polyvinyl chloride-based blends

73

Polyvinyl Chloride-Based Blends

3 Polyvinyl Chloride-Based Blends

Mihai Rusu and Daniela L. Rusu

3.1 Introduction

Polyvinyl chloride, commercially known as PVC, is a linear thermoplastic polymer. NormalPVC contains few (<10) branches per molecule and the existence of more than one longchain per molecule is not probable. The presence of a chlorine atom causes an increase inthe attraction between molecules and also of the hardness and stiffness of the polymer. Ithas a glass transition temperature (Tg) of 80 °C. PVC is capable of acting as a weakproton donor and thus effective solvents are weak proton acceptors, such as cyclohexanoneand tetrahydrofuran [1, 2].

X-ray studies show that PVC is substantially amorphous, although a small percentage (< 5%)of crystallinity is present. Studies using nuclear magnetic resonance (NMR) techniquesspecify that conventional PVC is about 55% syndiotactic and the rest largely atactic instructure. The presence of chlorine in great quantities in the polymer gives it flameretardancy properties [2].

Polyvinyl chloride is of high commercially interest, because of the accessibility to basicraw materials and of possessed properties [3]. The applications of this polymer are to acertain extent limited because:

1. It is characterised by low temperatures brittleness,

2. It has reduced thermal stability, and

3. It has a relatively narrow thermal processing range.

Many of these disadvantages can be reduced using the copolymerisation of vinyl chloridewith other monomers, frequently:

1. vinyl acetate (VA),

2. vinylidene chloride,

74

Handbook of Polymer Blends and Composites

3. acrylic monomers (acrylic acid, acrylic esters, methyl, ethyl methacrylate).

Copolymers can be processed at much lower temperatures, and therefore are less affectedby the work out operations.

The improvement of the processing characteristics and of the articles manufactured fromPVC was possible through association of the polymer with:

1. thermal stabilisers,

2. lubricants,

3. impact modifiers,

4. plasticisers,

5. processing aids, and

6. antioxidants.

These additive groups, with the exception of impact modifiers and processing aids, arein most cases micromolecular substances [2]. However, with the emphasis on theadvantages offered by the polymer blends, many of the micromolecular additives used inPVC-based compositions were replaced with macromolecular compounds.

The use of another polymer blended with PVC offers three advantages:

1. It improves PVC impact strength,

2. It improves its processability, and

3. PVC has a higher heat distortion temperature (HDT) than systems using liquidplasticisers [4].

Although the studies on PVC based blends focus mainly on the properties, there are alsonumerous investigations aiming to establish the degree of compatibility betweencomponents.

The range of macromolecular compounds for which compatibility was determined and/or used for processability and utilisation characteristics modification of PVC-basedcompositions is extremely wide and covers both general use polymers [polyethylene,chemical modified polyethylene (PE) and ethylene-based copolymers, polypropylene (PP)and propylene copolymers, polystyrene (PS) and styrene-based copolymers, acrylic

75


polymers and copolymers, polyvinyl acetate (PVAc) and its derivatives, different types ofgeneral use elastomers] and engineering polymers (polyamides and copolyamides,thermoplastic polyesters and copolyesters, polycarbonates and, polyacetals).

3.2 PVC/Polyalkene Blends

The difference between solubility parameters of PVC (δPVC = 21.7 J1/2 ⋅ cm3/2) andpolyethylene (δPE = 16.4 J1/2 ⋅ cm3/2) is an indicator of the incompatibility of these polymers,which is also confirmed by the morphology and poor mechanical properties of the PVCblends realised with different sorts of PE [5–7].

Although the PVC/PE blends are heterogeneous and with low mechanical properties,they are interesting because:

1. They are characterised by superior processability,

2. They have good thermal stability,

3. They generate a small amount of chlorine acid when burned, and

4. They have better dielectric properties than PVC.

A great interest for PVC/PE blends is in electrets production, characterised through long-term stable polarisation (sometimes even several years [8]). Such electrets are used inmanufacturing air filters for air-conditioning devices and vacuum cleaners.

The introduction of liquid plasticisers (dioctyl phthalate; DOP) is followed by morphologymodification of PVC/PE blends, which continue to have a heterogeneous structure, afact sustained by the negative deviation from additivity in the diagrams representingmelting viscosity variation versus PVC proportion in the blends [9].

To enhance PVC/PE blend properties, Nakamura and co-workers [10, 11] studied thepossibility of components static co-crosslinking (30 minutes pressing at 100 °C), to increasephase separation area resistance. As a co-crosslinking agent they used a system based ontri-allyl cyanurate and α,α´-bis(t-butyl peroxide)isopropyl benzene peroxide.

The results showed that using 0.25 wt% peroxide and 4 wt% tri-allyl cyanurate gave thePVC/PE (2:1 parts) blend, a significant increase of tensile strength and elongation, higherperoxide proportions having little effect on the previously specified characteristics.

The same attempt was made by Rudin and van Ballegooie [12], using reactive extrusion,who obtained little difference from the Nakamura results that were related to the type of

76


PE [linear low density polyethylene (LLDPE)] and the different molecular weights ofthe polymers used.

The improvement of properties, as well as availability area extension of the PVC/PEblends was also achieved by using compatibilisers similar to grafted/chlorinated PE(CPE) or copolymers.

A mixture of PVC, high-density polyethylene (HDPE) and CPE was found suitable formanufacturing weather-snipping gasket for automobile windows.

Blends that comprised PVC, PE and a polymer derived from at least 80 wt% acrylic oralkyl, aryl, alkaryl, or methyl methacrylate ester and not more than 20 wt% acrylic orstyrenic monomers, were used for extrusion or injection moulding of pipes or pipefittings, garden tools, electrical, automotive and business machines or appliance parts,toys, sporting goods, footwear, battery cases, conducts, construction profiles for medicalapplications, automotive or furniture seating, wall coverings and bottles [13].

Another way to enhance PVC/polyolefin (PO) blend properties is chemical modificationof the components using substitution or grafting. The best example is PE chlorination.

There is a considerable body of literature concerning the changes in properties andcompatibility of PVC/CPE blends [4, 14–19].

The studies, using a great number of characterisation methods [viscometric method,dynamic mechanical analysis (DMA), thermal analysis, electron microscopy, gaspermeation, etc.], have demonstrated that the PVC/CPE blend compatibility dependsmainly on: chlorine content, its distribution on the PE backbone, chlorination method,the degree of residual crystallinity from CPE, and the proportion of CPE in the blend[4, 14–19].

CPE containing less than 25 wt% chlorine are incompatible with PVC and are generallynot used in PVC blends. Those with 24–40 wt% chlorine are the best impact modifiersbecause they have practical miscibility [19]. CPE with 45 wt% chlorine are misciblewith PVC with lower critical solution temperature behaviour (LCST).

The usual chlorine content in CPE from PVC/CPE blends varies between 25–40 wt%and a content of 36 wt% is known to provide the best impact strength [18].

Chlorinated PE with a high chlorine content (45–48 wt%), produced by solutionchlorination, with a statistical distribution of the chlorine atoms and a reduced degreeof residual crystallinity is more compatible with PVC than the same polymer producedby suspension or fluidised layer chlorination [17, 18].

77


Depending on the mixing ratio, the blend toughness varies from that of PVC to CPE, theheat resistance and heat distortion characteristics are nearly independent of CPE contentand outdoor weathering characteristics are similar to those of PVC. The electricalproperties, chemical and flame resistance of those blends are equivalent to those of PVC.

DOP as a plasticiser in PVC/CPE blends gives these polymers an increased degree ofcompatibility [20].

The mixtures of PVC, CPE and coal tar pitch were used as weather resistant roofingsheets. Inserting methyl methacrylate-butylacrylate copolymer in PVC/CPE blendsprovides excellent tensile and impact strength.

Remarkable results regarding the impact strength of the PVC/CPE blends were alsoobtained with addition of diamine (0.1–10 wt%) [13].

The impact strength of PVC/CPE blends was also increased considerably by addingmodifiers with elastomeric properties [copolymer ethylene with VA [21], various butadieneand butadiene-acrylonitrile oligomers, acrylic resins [22–24], ethylene-propylene-dieneterpolymer [18] and hydroxy-terminated polybutadiene (PB) [18], epoxidated naturalrubber [25, 26]]. The elastomeric additives produced better adhesion between thecomponents of the boundary interfacial surface. The introduction of epoxidated naturalrubber in to the PVC/CPE blends ensures the improvement of the antivibrationalcharacteristics [25].

It has also been proved to have good physical and mechanical properties and goodprocessability characteristics PVC/CPE blends charged with different filling materials(wood flour, kaolin, calcium carbonate).

PVC/CPE blends containing or not other additions (elastomers, filling materials,plasticisers, etc.), are suitable for the manufacture of sheets, shaped articles, films, blocksand coatings. The main processing procedures suitable for turning this blend into differentproducts are extrusion, injection, calendering, thermoforming and pressing. The processingshould be done at well-specified temperatures. The recommended extrusion temperatureis 150–175 °C, but when extruding window profiles the required impact strength isachieved only at 190–195 °C. For calendering and thermoforming, temperatures of 165–190 °C and 150–175 °C (mould temperature 60–70 °C) have been used, respectively.Compression moulding of blocks and sheets should be carried out at 175 °C and 120–130 °C, respectively. For injection moulding a melt temperature of 170–180 °C and amould temperature of 20–50 °C are recommended [20].

Applications of PVC/CPE blends include profiles for windows, guttering, street barriers,gas pipes, bench slats, sheet for facades, balcony cladding, chemical plant, refrigerators,

78


traffic signs, foil for identification and punch cards, flame retardant wall coverings, cases,prams and automobile interiors. Injection moulded components include extractor hoods,gullies in sewage systems, guttering parts, caps for road reflectors post and bench slats.

PVC/CPE blends are mainly used for outdoor applications, but are limited by the prevailingclimatic conditions. Performance has been satisfactory for more 30 years in countrieswhere the mean annual temperature during the hottest month is not greater than 24 °C.Under these conditions the blends show good impact resistance over the whole temperaturerange encountered in the applications, as well as being resistant to ageing, UV andweathering over the intended period of use. The upper temperature is 60–65 °C [20].

The PVC/sulfochlorinated polyethylene and PVC/CPE blends have similar properties,good processability, stability, impact strength and chemical resistance. They are usuallyprocessed by injection moulding, resulting in products suitable for the same applicationareas as PVC/CPE blends [13].

There have been many studies on the compatibility and properties of blends made ofPVC and PE copolymers. Most of them focus on PVC/ethylene-vinyl acetate copolymers(EVA) [27–37].

Gradually increasing the content of VA in EVA converts them from crystalline, nonpolar,rigid materials, into amorphous, polar rubbery materials. In blends of PVC with EVA,there may be separate phases from crystalline PVC, amorphous PVC, crystalline PE blocks,amorphous EVA, and one or two phases for molecular blends of amorphous PVC withamorphous EVA. The concrete morphology of PVC/EVA blends hangs on the VA contentin EVA, molecular weight and proportion of the components in blend, mixing conditions,and subsequent treatments the blends undergo [27–37].

The studies have confirmed that increasing the VA content in EVA increases the polaritycloser to that of PVC, which induces stronger interfacial bonding between phases andbetter miscibility of the two polymers. Simultaneous, increasing the VA content in EVAdecreases the PE crystallinity, making the polymer softer and more flexible. These twoeffects determine the efficiency of EVA as an impact modifier in rigid PVC, and as apolymeric plasticiser in PVC.

These affirmations have been confirmed by many studies emphasising that EVA of 50–80 wt% VA content produced maximum miscibility with PVC [32]. From DMA anddifferential scanning calorimetry (DSC) it has also been found that EVA with 45 wt%VA tends to mix with PVC on molecular scale when the content of the sample is greaterthan 25 wt% [33, 37].

79


When PVC was blended with 0–25 wt% EVA as impact modifier, synergistic peakimprovement occurred at 5–15 wt% EVA. At higher VA content in EVA, the peak tendsto move toward higher EVA content and becomes broader [38]. Electron microscopyshowed that increasing EVA content, gives rise to EVA domains whose size grows, untilphase inversion made the EVA continuous matrix phase and its properties transposefrom rigid high-impact plastics to thermoplastic elastomers [36]. For blends with betterimpact strength, the optimum VA content seems to be about 45 wt% [34]. Copolymershaving over 65 wt% VA are good plasticisers.

Research shows that addition of lubricants to PVC/EVA blends causes shifting of themaximum peak plotted in the curve showing the influence of EVA content on impactstrength [39].

When chlorine is introduced into the EVA copolymer, the compatibility with PVC issignificantly improved, but the rubber character of EVA is simultaneously stronglyinfluenced [34].

PVC blends with ethylene-VA-carbon monoxide copolymers (EVA-CO) were alsodisclosed. In these copolymers VA is the flexibilising monomer, and along with thecarbon monoxide it increases the polymer polarity so that it becomes completely misciblewith PVC [40]. The PVC/EVA-CO blends are transparent with excellent Izod impactstrength [40].

PVC/ethylene-ethylacrylate copolymer blends were found to be immiscible. The inclusionof carbon monoxide was able to improve the miscibility of ethylene-acrylic monomers(ethylacrylate, butylacrylate) copolymers with PVC [41]. A similar improvement inmiscibility was also observed in EVA – sulfur dioxide terpolymer [41]. These blendsshowed better processability, reduced rigidity, enhanced toughness and mechanicalperformance.

Because ethylene-carbon monoxide copolymer (COPO) is prone to photodegradationby ultraviolet light (UV), the PVC/COPO blends can be used to produce packagingmaterials with calibrated lifetimes for exposure to sunlight.

In addition, PVC blends with ethylene-propylene-diene monomers (EPDM) and ringopen polynorbonene with carboxy and carboxylic ester groups were reported. Theseblends were moulded into sheets with excellent impact resistance.

Commercial PVC blends with EVA copolymer grafted with vinyl chloride, (EVA-VC)have been used since the 1970s as a high impact strength rigid formulation [13].

80


Mechanical mixing, suspension polymerisation of vinyl chloride in the presence of EVAlatex, or compounding EVA-VA graft copolymer (comprising 50 wt% EVA) with PVC togive a final content of 5–15 wt% EVA, are the most usual blending techniques. Thisblend shows high hardness, rigidity, and adequate heat, chemical and flame resistance.The toughening effect can only be achieved, however, if the copolymers have low Tg andits separate phase consists of homogeneously distributed drops of optimised averagediameter.

The PVC/EVA blends are used for window profiles, roof gutters, drain pipes, profiles forbenches and fences, light panels, road sign posts, panels for facade cladding, ventilationsystems, for chemical waste, gas or draining pipes, for cable jacketing and cable conducts,thermoforming sheets, fitting, covers, bottles, and containers [13].

PVC and chlorinated PVC (CPVC) are antagonistically immiscible with PP. Accordingly,there are few studies on PVC/PP blends. These studies emphasised, however, that addinga little PP to the rigid PVC compositions gives them better processability and impactstrength [18]. The PVC/PP blends show a layered, wood-like structure.

Replacing PP with PVC-PP copolymer, the blends obtained can be calendered into goodimpact strength sheets.

3.3 PVC/Polystyrene or Styrene Copolymer Blends

Polyvinyl chloride is immiscible with PS, the blends of these polymers having a biphasicstructure and poor mechanical properties [4, 42–49]. However, taking into account theindividual performances of each of two polymers, it has been proved that the PVC/PSblends are interesting both theoretically and practically. For example, a reduction ofelastic properties of PVC melts was reported, coupled with improvement of certain opticaland physical properties on blending with PS [48].

The blends obtained as a result of styrene polymerisation in the presence of PVC are alsoheterogeneous, but with superior mechanical properties compared to those made bymechanical compounding [50].

An improvement of the mechanical properties of PVC/PS blends can be achieved byadding compatibility agents such as: styrene-ε-caprolactone copolymer, styrene-methylmethacrylate diblock copolymer [51, 52], styrene-butadiene-epoxided styrene triblockcopolymer [53], methyl methacrylate-styrene-methyl methacrylate triblock copolymer[54], PVC grafted with styrene [55], and styrene-butadiene copolymer grafted withcyclohexyl methacrylate [56].

81


There are many studies referring to blends comprising PVC, binary or tertiary copolymersof styrene. Among binary and tertiary copolymers, the most used in PVC blends arethose with acrylonitrile (ACN) and maleic anhydride.

Information in the literature referring to the compatibility of PVC with styrene-acrylonitrilecopolymer (SAN) is contradictory, some authors asserting their immiscibility [4, 57],others that they are miscible [58]. One thing was clearly established: SAN containing70–75 wt% styrene was found to provide useful polyblends. As little as 7.5 wt% SAN inthe PVC/SAN blend provided adequate mechanical strength and processability forcommercial applications [59].

The addition of SAN copolymer in PVC based compositions gave a thermal stabilityreduction [60, 61].

Styrene-maleic anhydride copolymers (SMA) as well as other polar styrenic copolymersare partially miscible with PVC [62]. Partial miscibility extends mutually to approximately10 wt% of either component. At higher concentrations, the mixture separates into atwo-phase system with neither phase being a pure component. The two phases differonly in the relative content of each pure component and are sufficiently chemically similarto exhibit significant microscopic adhesion between the phases. This adhesion betweenphases accounts for the favourable balance in mechanical properties attained.

The partial miscibility between PVC and SMA copolymers provides for a family of heatresistant, fire-retardant alloys spanning the heat resistance range of low-end engineeringthermoplastics. SMA copolymers systematically decrease the melt viscosity of PVC topromote flow and processability in alloy compositions. This flow promotion isaccompanied by an increase in heat resistance rather than the usual heat sacrifice fromtraditional flow additives for PVC.

The adhesion between phases is particularly evident in the exceptional impact strengthderived from alloys of SMA copolymers with PVC. The impact strength is superior toany of the competitive engineering thermoplastic as well as injection moulding gradesof PVC.

Among the ternary copolymers with styrene units suitable for PVC mixing, acrylonitrile-butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS) copolymersare most commonly used.

There were several studies of PVC/ABS blends, the results being in detail discussed in[13]. Up to this point, will be shortly emphasised some aspects regarding miscibility,mainly properties and application fields of PVC/ABS blends.

82


If at beginning the name ABS was assigned to copolymers comprising different proportionsof acrylonitrile, butadiene and styrene manufactured using several methods, now theyconstitute a generic denomination for a wide class of such polymeric materials. Becausemany studies referring to PVC/ABS blends do not present information about thecomposition and manufacturing method of ABS, the various results are obtained.Accordingly, while some authors treat PVC/ABS as being compatible, others assert onlya partial miscibility of PVC with ABS copolymers [4, 63-65].

The different opinions regarding the PVC miscibility with ABS copolymers did notinfluence, however, the common consent that as a result of the mixing of these polymers,materials with good tensile and impact strength, improved processability, suitable densityand high heat deformation temperature are obtained [13]. Adding 15 to 20 wt% ABS toPVC composites gives optimal characteristics.

The PVC/ABS blends offer excellent processability and they are formable by all standardmethods. They have been used to produce housing for electrical tools, electrical andelectronic equipment housing, mouldings for domestic appliances, aircraft, computers,business machines, impact resistant blow mouldings, divers automotive items, pipes andprofiles, industrial tools, plugs and receptacle covers.

Terpolymers of methyl methacrylate, butadiene and styrene (MBS) are similar to ABS,having a rubber dispersed phase and a plastic matrix. The studies of Tg, impact strengthand morphology of PVC/MBS blends conclude that the blends are immiscible [66]. Theimpact strength reaches a peak at 20 wt% MBS concentration, with a value much higherthan either MBS or PVC individually. MBS can be used as an impact modifier, despite itsimmiscibility. This is explained by the strong adhesive bond between MBS and PVCphases [3, 4, 67].

Newer type of MBS, designed as modifiers for PVC, have controlled size of elastomericparticles that make it possible to prepare transparent PVC/MBS sheets for packaging.For example, MBS with cluster-like structures is being offered. The individual particleforming the cluster has a diameter of 50–70 nm. They are held together by styrene-methyl methacrylate graft copolymer or terpolymer.

3.4 PVC/Acrylic Blends

The term acrylic describes a family of polymers or copolymers containing repeating unitsthat can be considered as derivatives of acrylic or substituted acrylic acid.

83


Aspects of PVC compatibility with acrylic polymers are discussed in Chapter 9. In thefollowing sections only the properties and application areas of the PVC/acrylics blendswill be presented.

A bulk analysis of PVC/acrylics blends denotes that by choosing the appropriate acryliccomponent one can assure an extremely wide area of properties like tensile strength,impact strength, low-temperature flexibility and blocking resistance, low-temperatureimpact behaviour, high HDT and toughness, good transparency, flame resistance, weatherresistance, chemical and solvent resistance, craze resistance, thermal stability and goodprocessability [13].

The PVC/acrylic blends can be obtained using all classical polymer-processing techniques(extrusion, injection moulding, calendering, pressing, thermoforming, etc.), with specificparameters for each type of blend.

PVC/acrylic extruded sheets have been used for thermoforming applications. Ease ofthermoformability, toughness, resistance to cleaning solvents and flame retardancycharacteristics of the blend have been the primary features leading to its use. The inherentflame retardancy and low smoke-generation characteristics of PVC/polymethylmethacrylate (PMMA) blends meet the aircraft fire safety standards. These aspects,coupled with low-cost, led to use in aircraft and mass-transport vehicles.

PVC/acrylic blends have been used to form industrial, commercial and consumer goods,(e.g., as wall coverings, corner guards, column covers, shelving, counter laminates, chairs,seats, trays, ceiling tiles, window frames, weather boards, roof gutter systems, pipes,swimming pools, ladders, claddings), in medical, electrical (cable ducts and conduits)and diverse engineering equipment, for food or beverage equipment, as aircraft or masstransit interior components, for powder tool housing, razor bodies, vacuum cleaner parts,protective helmets, steering wheels, records, toys, sport articles, aircraft componentssuch as toilet bowls, floor pans, air diffusers, emerging respirator enclosures, officeequipment and computer parts, and other applications requiring good resistance toweathering [13].

3.5 PVC/PVC and other Vinylic Polymer Blends

Although the classical definition of a polymer blend states that the components arechemically different [68], there are, however, several PVC blends affiliated to this polymericmaterials group.

84


Casy and Okano [69] showed that the 50/50 blend of quite higher molecular weightPVC (HMW-PVC) and relatively lower molecular weight PVC (LMW-PVC), of whichthe mathematical viscosity is equal to the medium molecular weight PVC, has a bettermelt flow index than the medium molecular weight PVC for injection moulding.Yamamoto and co-workers [70-71], and Kawakami and co-workers [72] find the sameresult, and furthermore, they established that the tensile strength and tensile modulus ofblended PVC are enhanced with increasing low molecular weight (LMW)-PVC contentand decreasing molecular weight of LMW-PVC. Hence, tensile properties, are affectedby molecular weight distribution (Mw/Mn) of blended PVC. The impact strength diminisheswith increasing LMW-PVC content, and, especially with decreasing molecular weight ofLMW-PVC. They have also found that the blends of HMW-PVC and LMW-PVC haveimproved thermal stability and processability [70-71].

Plasticised PVC membranes have been widely used as sensitive layers in potentiometricand fibre-optic ion sensors. More recently, carboxylated PVC (PVC-COOH) whichcontains 1–2 wt% carboxyl groups in the side chain of the PVC has attracted muchattention as a novel class of material for chemical sensor membranes [72, 73]. Given thisinformation, Babu and Gaikar [74] studied the possibility of making new ultrafiltrationmembranes based on PVC/PVC-COOH blends.

Using several methods, the authors first underlined the good compatibility of PVC andPVC-COOH, related to the same chemical nature and/or because of specific interactionsbetween C=O and Cl-CH groups.

The PVC/PVC-COOH (10/1) blend membranes, additivated with various solvents (methanol,ethanol, butanol, cyclohexanol, ethyl acetate), gave a higher flux (85–95 l/m2⋅h) and analogousrejection efficiency (94%) compared to PVC and CPVC membranes alone. The pore sizeof blend membranes in the range of 2 to 21 Å was also found to be suitable forultrafiltration.

Although there are contrary opinions, many studies highlighted the incompatibility ofPVC with PVAc and the fact that the degree of miscibility also depends upon the methodof manufactory the blend [75–77].

Even if they are characterised by good processing properties, PVC/PVAc blends havepoor mechanical properties and, as follows, limited use. This inconvenience may beavoided if, in making PVC/PVAc blends, the mechanical mixing of the constituents isreplaced with VA polymerisation in the presence of PVC. A similar effect can also beachieved if the blend with mainly components is associated with elastomers as:polyisobutylene (PIB), polyethersulfide, polychloroprene (CR), polyisoprene (IIR),butadiene-butylacrylate-styrene or vinyl chloride-ethylacrylate copolymers. The blends

85


show good overall performance, with particularly significant improvement in transparencyand impact strength [13, 77].

The homogeneity degree of PVC/PVAc blends can also be improved by application incertain conditions of heat treatment [78, 79].

McNeill and Jameison [80] have studied the immiscible PVC/PVAc blends bythermogravimetry and thermal volatilisation analysis and have concluded that HClproduced by the dehydrochlorination of PVC migrates into PVAc phase and causesaccelerated deacetylation of PVAc. Other studies [81] confirmed this conclusion.

Studies referring to PVC/polyvinyl alcohol (PVA) underlined that these two polymershave a limited miscibility, a better degree of miscibility being observed to outermostparts of the composition domain, 90/10 and 10/90 PVC/PVA, respectively.

Showing thermal stability and good processability, PVC/PVA blends can be used forcovers, synthetic fibres and blow moulding.

PVC/PVAc blend compatibility is determined by the nature of used aldehyde(formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde) and degree of PVCacetalisation. For PVC/polyvinyl formal blends, an acetalisation degree of between 65%and 78% guarantees good compatibility for the components. PVC/polyvinyl ethanolblends have good processability and are used in the electrotechnique industry.

3.6 PVC/Engineering Polymer Blends

Because of the great number of PVC/engineering polymer blends, in the following pagesonly compositions that include polyesters, polycarbonates, polyalkylene oxide, and liquidcrystal polymers (LCP) are discussed.

3.6.1 PVC/Polyester Blends

PVC/polyester blend morphology and properties are mainly subjected to type (aliphatic,aromatic or aliphatic-aromatic), structure (CH2:COO ratio) and molecular weight ofpolyesteric component.

If only PVC/aliphatic polyester (PEST) compositions are taken into consideration, theoreticcalculations demonstrated that the blends show a miscibility window between CH2:COOof 4 to 10 [82]. There are two types of hydrogen bonding governing the miscibility

86


between PVC and PEST; one is the interaction between hydrogen of the methylene andchlorine of PVC, and the other is the interaction between a hydrogen of PVC and carbonylgroup of PEST. It is difficult to separate quantitatively two attractive interactions, whichincrease an approach to zero as CH2:COO increases [83].

Upon overall consideration, at low values of the CH2:COO ratio, there is a strongattractive interaction within polar PEST molecules and self-association results in blendmiscibility. As the value of the CH2:COO ratio is increased, the intermolecular interactionbetween PVC and aliphatic PEST begins to overcome the self-association energy ofPEST. Although the energy should be definitely weak, because the intramolecularinteraction in PEST is not usually classified as strong self-association, the energy shouldbe stronger at lower CH2:COO ratio. The blend with a CH2:COO ratio value between5 and 7 shows an optimum in intermolecular interactions. The maximum miscibilityappears at a CH2:COO ratio of 6, where binary intermolecular parameter (B fromequation ∆Hmix/V = Bφ1φ2, where ∆Hmix is the enthalpy of mixing; V is the total volumeof the blend; φI is the volume fraction of component 1) was equal to –3.85 cal/cm3. Athigher values of the CH2:COO ratio, the interaction, and correspondingly begins toshow immiscibility. It has been reported for PVC/aliphatic PEST blends that theimmiscibility at high carbonyl content may be due to an unfavourable balance ofintramolecular interactions mostly occurring between methylene and carbonyl groups.In the immiscible region, because of the lack of favourable interactions, entropy effectssuch as unfavourable free volume effect should become more prominent, which werenot at all considered in the calculation.

The trend of interaction parameters from molecular dynamics simulation is generally inaccordance with those by the modified Guggenheim quasi-chemical method, except thatthe minimum of the B value is located at a CH2:COO value of 3.

Coleman and co-workers [84] used a solubility parameter method, modified with anadded term to account for the presence of favourable intermolecular interactions inpolymer blends. For a PVC/aliphatic PEST blend the optimum miscibility is located at aCH2:COO ratio of 3.5. In the framework of the miscibility guide they suggested, themiscibility is dependent on the balance between the favourable strong interactions, likehydrogen bonds, and the physical interactions, which in general are unfavourable.

Experimentally, the maximum miscibility by melting point depression method is locatedaround CH2:COO ratio of 7 [83]. Riedl and co-workers [85] have reported that for thethermodynamic study of this system by inverse-phase gas chromatography at 100 °C,the B values are dependent upon the methylene:carbonyl ratio, reaching a minimumvalue of 5, which corresponds to a PVC/poly ε-caprolactone (PCL) blends.

87


The position held by PCL in the aliphatic PEST series justifies the great number of studiesreferring to the system PVC/PCL [86–96]. From these studies, the blend system has beenfound to be miscible, in the amorphous or molten state, throughout the entire compositionrange 10–90 wt% PCL. These studies have also shown that some PCL becomes crystallineupon solidification in blends with 40 to 50 wt% or more PCL present.

Thus, PVC/PCL blends having less than 40 wt% PCL are homogenous, given to the fullcompatibility of the system components. In this kind of blend PCL acts as macromolecularplasticiser. The blends where the PEST component ratio exceeds 40 wt% have a complexstructure, being constituted from a mixture of homogenous PVC/PCL blend, withamorphous structure, associated with crystalline and amorphous domains of PCL. PVCis excluded from PCL crystallites, but remains in the interstitial areas of semicrystallinematerials [86]. The proportion of crystalline domains, the shape and size of PCL crystallitesfrom PVC/PCL blends having more than 40 wt% PCL depends on the molecular weightof the components, the real proportion of PEST component in the blend, of the methodobtaining the blend, thermal treatment and mechanical stress that the blend undergoes[89, 94–98]. Blends achieved by solution casting exhibit a greater degree of crystallinitythan those obtained by melting. Stretched films have a greater degree of crystallinitythan unstretched films. The stretching primarily involves the structural transformationof crystalline PCL from lamellae to microfibrils [94].

In solution, it was found that PVC and PCL are compatible over the whole range ofcomposition [91–93]. The characteristics of the solutions containing PVC/PCL blendsdepend on the nature of solvent [93].

PVC/PCL blends can be readily prepared by a hot compounding process. The compositionsare flexible, transparent, plasticised products [87, 99]. PVC partially destroys PCLcrystallinity. Thus, blends of two rigid polymers become soft and pliable compositions.However, at high PCL content (>40 wt%), the blends become translucent and more rigidbecause PCL crystallisation at time elapses. This effect is dependent on blend composition.

Although in many blends based on PVC, aliphatic polyesters operate as macromolecularplasticisers [99], the literature offers few studies that clearly show the influence of suchplasticisers on blend properties.

All PVC/polyneopentyl glycol adipate blends are transparent and showed one Tg. Theoptical clarity of the blends and the existence of one composition-dependent Tg wereevidence that polyneopentyl glycol adipate is miscible with PVC. All blends remainedtransparent when heated to 220 °C. Added in 5 wt% proportions to PVC compositions,polyneopentyl glycol adipate also acts as a thermal stabiliser [82]. The same effect was

88


recorded for PVC/polytetramethylene sebacate blend with a small proportion of aliphaticpolyester [100].

For PVC/polyethylene adipate blends, it was found that at reduced proportions of polyestericcomponent, an improvement of thermal stability is also established. Over a wider range ofblend composition, however, the thermogravimetric analysis results show complexbehaviour, with initial stabilisation of the polymer, seen at lower polyethylene adipatecontents, being replaced by marked destabilisation at a higher polyester content [101].

Hourston and Hughes [102-103] and Nishi and co-workers [104] studied acoustic dampingof PVC/polytetramethylene terephthalate – polytetramethylene ether glycol terephthalateblock copolymer. This segmented polyether ester (Hytrel 4055) is a block copolymer withcrystallisable tetramethylene terephthalate hard segments and polytetramethylene etherglycol terephthalate soft segments. Dynamic mechanical studies indicated that blendscontaining 25–50 wt% Hytrel were completely miscible, a single glass transition point wasobserved; but, as the Hytrel level was increased to 60 and 65 wt%, a shoulder becomesapparent on the low-temperature side of the glass transition peak. Finally, at 80 wt%Hytrel, two peaks were observed, indicating immiscibility of the blend. The Tg of PVC/Hytrel blends was found to decrease with the amount of added Hytrel [105, 106].

PVC/Hytrel blends are used in flexible hose manufacture and electrical cable insulation.

Park and co-workers [107] studying PVC/polyethylene glycol glutarate – polytetramethyleneglycol terephthalate block copolyester blends have emphasised the good impact strengthand processability of these materials. Blends with more than 4 wt% from this blockcopolymer have also high thermal stability.

Polyethylene terephthalate – caprolactone copolyesters are miscible with PVC only if thepolyethylene terephthalate (PET) content is between 35 and 44 wt% [108].

The blends of PVC with aliphatic polyester – aromatic polyester block copolymer (Perprene1002 from Toyobo Corp.), with physically crosslinked structures and service temperatureof 125 °C, were found useful for manufacturing heat-resistant insulation for electriccables [13].

PVC blends with semi-aromatic copolymers obtained by reacting PET with polybutyleneglycol and 1,4-butanediol are homogenous and have good low-temperature impactproperties [13].

Among thermoplastic polyesters, polybutylene terephthalate (PBT) – polytetramethyleneoxide (PTMO) block copolymers were reported to exhibit partial compatibility withPVC at room temperature, and in fact they have been classified as permanent PVC

89


plasticisers [85]. Nishi and co-workers [109] attributed miscibility to the soft segment,without clarification as to the specific group causing it. Robeson [110] ascribedcompatibility to the proton-acceptor potential of the ester carbonyl from PBT segmentby analogy to other polyester – PVC miscible blends.

Mixtures of PVC and PBT – polytetrahydrofuran (PTHF) block copolymers have beenreported to exhibit at least partial miscibility [111]. These block copolymers are excellentpermanent plasticisers for use in more demanding plasticised applications. These includethe examples previously cited for plasticised PVC with particular emphasis on shoecomponents, where abrasion resistance is important. PVC/PBT – PTHF copolymer blendshave been used in agricultural insecticide hose jackets to obtain better low-temperatureflexibility and abrasion resistance than typical plasticised PVC [112]. These blends havebeen used in interior automotive upholstery, food packaging film, wall coverings, flooring,and wire and cable coatings. PBT – PTHF block copolymer, is also used as a permanentplasticiser for PVC with better thermal stability, better release from highly polishedchrome-plated processing rolls, and the ability to use higher shear mixing screws inextrusion processing.

Addition of a relatively small amount of polypropylene terephthalate has given improvedprocessability, thermal, irradiation and impact resistance compared to that of neatPVC [13].

PVC/PBT blends with a small ratio of polyesteric component are homogenous, whilethose with great amounts of PBT induce biphasic mixtures, where a phase is homogenous,amorphous, arising from PVC/PBT blend and the other crystalline, from PBT [110].

With the commercial demand for plasticised PVC compositions of greater permanencyfor more demanding applications as well as for freedom from ecological implication ofplasticiser migration into the environment, recent emphasis has been placed on readilyavailable intermediate molecular weight plasticisers (Mn = 2000–4000). These oligomersare generally polyester types, e.g., adipate or adipic acid and ethylene glycol. Examplesof those oligomers are cited in reference [113] and will not be discussed in detail becausethe molecular weights are generally lower than the systems covered in this chapter.

3.7 PVC/Polycarbonate Blends

With relatively similar structure as aromatic PEST, bisphenol A polycarbonate (PC) provedto be incompatible with PVC [114]. However, to make these blends useful, systemcompatibilisation using polydimethylsiloxane (PDMS) multiblock copolymer orbis(hydroxyphenyl)-hexafluoropropane – PC (6F-PC) has been tested.

90


Gorelova and co-workers [115] studied the surface composition of PVC/PC/PDMS blendsand observed the formation of transparent solvent cast films from some of them. Papkovand co-workers [116, 117] discovered the same. This finding is interesting because thereflective indices of PVC, PC and PDMS are different and, consequently, transparency ofthe blend films may suggest miscibility of their constituents, despite the fact that PVC isindividually incompatible with both PC and PDMS. Another possible explanation ofthis event is that these blends are pseudocompatible and their transparency is caused bythe very small size of the dispersed block copolymer phase. As is already known, such anoptical effect can occur if the size of the dispersed phase particles does not exceed about100 nm. If this is the case, at certain blend compositions, specific conditions could arisethat lead to a very high level of dispersed PC/PDMS blend in the PVC matrix.

Adding at least 15 wt% 6F-PC to the PVC/PC blend, a homogenous mixture with asingle Tg is formed. These blends are flame-resistant, and are also resistant to acids,bases and many organic solvents. These mouldable, transparent and fireproof alloys hadthe stability and strength of PC and processability of PVC. They were used for packaging,bottles, parts of medical and chemical instruments, and for hot water pipes [13].

Theoretical calculations estimate that for PVC/polyalkylene oxides blends a compatibilitywindow exists at CH2:O ratios between 2 and 4. Experimental data have partiallyconfirmed this fact [118, 119]. Experimental evidence showed that only polyethyleneoxide (PEO) melt in PVC-rich compositions showed compatibility [120, 121]. The degreeof miscibility depends on molecular weight of the components from system and testingtemperature. Morphological, dynamic mechanical, thermal and other propertiesinvestigated, indicate that PVC/polypropylene oxide (PPO) blends are incompatible,whereas PVC/PTMO system shows miscibility in the melt [120, 121]. A literature surveyrevealed that PTMO and PPO have been tested as modifiers for PVC. However,experiments were not designed to investigate compatibility, and the results (impact strengthenhancement, melt index decrease, and PTMO melting point depression) could not providean unambiguous with respect to mutual compatibility.

The investigation made on a PVC/copolyester of 60% mol p-hydroxybenzoic acid and40% mol PET [122] showed that tensile strength and modulus appear to increase withincreasing LCP content for the blend with an LCP content lower than 15 wt%, and theydecreased significantly with further increasing LCP content. Thermal analysis indicatedthat PVC and LCP are partially miscible for the blends containing an LCP content lessthan 15 wt%, and miscibility at an LCP content above 15 wt%. The torque measurementshowed that the viscosity ratio between the LCP and PVC matrix is much smaller thanunity. Scanning electron microscopy (SEM) observation revealed that fine fibrils are formedonly in the skin layer of the mixtures with an LCP content below 15 wt%. The coresection of these blends exhibited an ellipsoidal feature. Two-phase morphology

91


disappeared in PVC/LCP blends with an LPC content above 15 wt% owing to thedecomposition of the LCP during injection moulding. In this case, the mechanical strengthof the PVC/LCP blends with the higher LCP content tend to decrease sharply withincreasing LCP content.

3.8 PVC/Elastomer Blends

Because of their nonpolarity, polybutadiene, polyisoprene, polyisobutylene and butylicrubbers are incompatible with PVC, therefore few studies referring to PVC/nonpolarelastomers blends can be found [123–127]. In order to enhance PVC – nonpolar elastomercompatibility, compatibilisation agents are added to the system [127], or are subjectedto chemical modification.

Among PVC/nonpolar elastomer chemically modified mixture, the PVC/epoxidatednatural rubber (ENR) blend was studied the most. Although in PVC/ENR blendselastomers with various epoxidation degrees have been used, in most cases natural rubberwith 50 mol% (ENR-50) epoxidation degree was used.

Epoxidated natural rubber with 50 mol% epoxidation is polar and has similar propertiesto synthetic elastomers [128]. These qualities generated interest in assessing thecompatibility of ENR with other polymers, particularly PVC [129–139].

It has been reported [129–134] that blends of rigid PVC with ENR-50 form a misciblesystem in which ENR-50 reduces Brabender torque [135] and melt viscosity of rigidPVC [131]. Both melt-mixed [131] and solution-cast [135] blends have been reported toexhibit a single Tg lying between that of PVC and ENR-50 [136]. The miscibility of PVCand ENR solid state has been established by the confirmation of hydrogen bonding fromFourier transform infrared spectroscopy (FTIR) studies [136] and synergism in mechanicaland dynamic properties [133, 134]. Rheological studies revealed the pseudoplastic natureof PVC/ENR blends [137]. Fracture studies also revealed that ENR-50 blends are capableof acting as impact modifiers for PVC [135].

Earlier work on PVC/ENR blends by Nasir and Ratnam [138] indicated the need to usesuitable mixing conditions to attain optimum properties. Similar observations have alsobeen reported by Ishiaku and co-workers [136, 137]. They found that using a BrabenderPlasticorder coupled with a mixture/measuring head for a PVC-rich blend, optimumproperties are obtained by mixing either at high temperature, say 150 °C, at low rotorspeed, or at higher rotor speed and lower temperature. On the contrary, for an ENR-richblend, optimum conditions are rather restricted to high temperature and low rotor speedonly. They also indicate that the choice of optimum blending conditions is not limited to

92


any particular temperature, mixing time or rotor speed. Rather, optimum blends can beobtained by selecting any set of conditions within a processing window (130–150 °C, 2–9 minutes, 20–50 rpm).

The clarity of the film or sheets made from the PVC/ENR-50 blend support the idea thatthe miscibility inferred from the melt state is equally true for the solid state. This statementis further supported by the observation of synergism in the tensile properties. The tensilestrength of the PVC-rich blend, i.e., 40–80 wt% PVC, exceeds the value expected if theproperties are merely additive [140]. A similar trend is also observed for elongation atbreak, where this exceeds the additivity line at all compositions [136]. Maximumsynergistic effects in tensile strength occurred around the 70 wt% PVC region, whichalso coincide with the observed increase in density. The sudden deviation from the observedtrends of such properties around the 70 wt% PVC composition range could also be areflection of improved packing.

The composition dependence of hardness of PVC/ENR-50 blends have illustrated that atlow PVC content, i.e., up to 40 wt%, the hardness of blends is between 30 and 70 IRHD,which is the hardness range for soft vulcanised rubber [136]. At these concentrations,the blends behave like a typical filled rubber system, in which ENR is the continuousmatrix phase. The properties are therefore rubber dominant with PVC acting as thefiller.

PVC/ENR blends are prone to thermo-oxidative ageing. This has been attributed toinitial PVC degradation, which releases HCl that catalyses the ring-opening reaction ofthe epoxided group. The combination of an optimum amount of antioxidant (2,2,4-trimethyl-1,2-dihydroquinoline (TMQ)), and has been proven to be effective in curingthe thermooxidative ageing and irradiation stability of the blends [138, 141].

To increase PVC/ENR flexibility the influence of different types of plasticisers (DOP,epoxidated soya oil (ESO), and ether-thioether (ETE)) on many characteristics of theseblends was also investigated [132].

Varughese and co-workers [132] concluded that melt mixed blends of plasticised PVCand ENR-50 have a phase morphology close to a single phase system. These blends havea single Tg lying between the Tg of the blend components as shown from DMA and DSCthermograms. Plasticised PVC has the maximum broadening in glass-rubber transitionof all the samples. The drastic reduction in Tg width of plasticised PVC with theincorporation of ENR may be due to uniform distribution of dibutyl phthalate amongENR molecules, which has joined with PVC particles. This reduction in Tg width fromplasticised PVC to the PVC/ENR blend suggests a more defined single-phase morphologyin the latter. Since the Tg of plasticised PVC/ENR blends is much lower than that of rigidPVC/ENR blends [131], the former have greater low temperature flexibility.

93


The tensile strength drops significantly with an increase in plasticiser concentration inthe PVC/ENR blends. ETE initially gives better strength at lower concentrations (below15 phr) followed by DOP, then ESO [136]. However, this trend is reversed at higherconcentrations. The decrease in tensile strength with increasing plasticiser content maybe due to the masking of the centres of forces holding PVC molecules together (the gelconcept), or it may be due to the lubrication effect, which makes it easier to pull chainsapart according to the lubricity theory.

In the case of elongation at break, DOP-plasticised blends show higher elongation atbreak at all concentrations, while other plasticisers do not perform so well, particularlyETE, which yield values well below acceptable levels at higher concentrations. DOP andESO, has reduced the tear strength significantly. This could be due to excessiveplasticisation, which makes it easier to pull the chains apart.

The presence of plasticisers modifies PVC/ENR blend thermo-oxidative behaviour. Theway this modification, shown by mechanical tests (tensile strength, elongation at break,tear strength, modulus, hardness), takes place, before and after degradation, depends onthe nature and proportion of plasticisers from system [136].

From the previous discussion, it can be inferred that each type of plasticiser has its ownpotential and limitations. For instance, the incorporation of DOP generally decreasesthe mechanical properties of the PVC/ENR blends, although it simultaneously stabilisesthe blend against thermooxidative degradation.

The improvement in the degradation properties of PVC/ENR with DOP incorporationimplies that presence of DOP is effective in altering the epoxided/heavy metal salt balance.According to the gel theory of plasticisation, the plasticiser breaks the loose attachmentsin PVC and makes the centres of force, consequently reducing the number of attachmentin the dynamic equilibrium of solvation and desolvation. This action is known to conferstability to PVC formulations and thus incidence of release of HCl is reduced.

Based on the narrowing of the glass transition region observed by Varughese and co-workers [132] in the DOP-plasticised PVC/ENR blend, it can be inferred that DOP isintimately miscible with ENR, as is the case with PVC.

Sulfur dynamic vulcanisation of PVC/ENR blend insures its transformation inthermoplastic elastomers (TPE). The addition than increase of sulfur amount results intensile strength, modulus, elongation at break, tear strength and hardness improvement,concurrently with swelling index reduction. Significant enhancement in resistance againstthermooxidative ageing has also been observed by sulfur incorporation in the plasticisedPVC/ENR TPE [136]. This has been attributed to the increase in crosslink density of thedynamically vulcanised TPE.

94


Several compositions of PVC/ENR/CPE blends using various types of CPE (22, 35 and45% chlorine contents), ENR-25, and ENR-50 were studied [140, 141]. The resultsobtained indicate that some compositions using amorphous medium chlorine contentCPE and ENR-50 have a good miscibility, mechanical properties, and a damping behavioursuitable for high performance vibration absorbers. Furthermore, flake-shaped fillers(graphite, mica) could be used to improve the damping behaviour of PVC/ENR/CPEblends [140].

The investigation carried out on DOP plasticised PVC and epoxidated 1,2-polybutadiene(1,2-EPB), epoxidated 1,4-polybutadiene (1,4-EPB) mixtures mainly tracked the co-stabiliser effect of the rubber in combination with metal soaps [Zn/Ca (2/1) stearates][142, 143]. It has been reported that 1,2-EPB exhibits good compatibility and finelydispersed into compound PVC as compared to 1,4-EPB and that epoxidated PB build upsynergistic blends with metallic soaps. The synergistic effect of 1,2-EPB is superior to1,4-EPB effect.

3.9 PVC/Butadiene-Acrylonitrile Copolymer Blends

This type of blend historically represents the initial observation that miscibility of polymermixtures is possible [144]. The investigations on this particular blend outnumber anyother miscible polymer blend. It is also the result of scientific and commercial interest inthis blend over the past five decades [144-204].

The great number of existent studies referring to PVC/butadiene-acrylonitrile rubber(NBR) blends take into account two aspects:

1. degree of compatibility of components and

2. practical use of this blend.

The compatibility of the PVC/NBR blends was studied by numerous methods [dynamicmechanical, dynamic viscoelastic behaviour, viscosimetric measurements, dynamic thermalanalysis (DTA), DSC, light scattering, gas permeability, density, stress-strain measurements,mechanical properties, optical and transmission electron miscibility].

Dynamic mechanical tests have been a common method of investigation PVC/NBR blendscompatibility [105, 106, 145, 148, 154, 205-209]. Nielsen [145] and Breuers and co-workers [148] found for PVC/NBR blends that a single maximum in damping occurs ata temperature between the corresponding temperatures of the pure components. Theyreasoned that the polymers were soluble each in other. Nielsen [154] concluded that the

95


broad damping peak found for a PVC/NBR blend indicated that the polymers weresoluble in each other, but the intermolecular attraction is so weak that considerableassociation of like segments is taking place in the soluble mixture. Nielsen also pointedout that in plasticised PVC, crystallites act as crosslinks preventing the rubber materialfrom flowing under load, even if it is not crosslinked by a chemical reaction, as invulcanised rubber.

Takayanagi and co-workers [155, 156, 163] measured the dynamic viscoelastic behaviourof PVC/NBR blends prepared in solution and recovered by evaporation of the solvent.

They concluded that even though the two polymers mix molecularly there is somemicroheterogeneity shown because of the different segmented environments. Matsuoand co-workers [161, 165] examined a mill-mixed blend of PVC with NBR containing8%–40% ACN. The results of the dynamic viscosity measurement were interpreted toindicate that a 20% ACN elastomer gave almost homogenous blends. Electron microscopypictures were interpreted to indicate that microheterogeneity existed even in the blendswith 40% ACN elastomer. Using DTA, Oganesov and co-workers [164] investigated thehomogeneity of mill-mixed blend of PVC with NBR containing 40% ACN. They cameto the conclusion that blends can be single or two phases depending upon the polymerratio. Feldman and Rusu [166, 168] examined the compatibility of PVC with NBRcontaining 40% ACN by viscosimetric measurements of a blend solution incyclohexanone. They found that the polymers are compatible. Vasile and co-workersarrived at the same conclusion [196, 209], using the same viscosimetric method for PVC/NBR blends with 38% ACN elastomer and a Mooney plasticity of 45. Krause [170], inher review on polymer compatibility, lists the combination of PVC with NBR ascompatible.

Using DTA and DMA, Jorgensen and co-workers [175] demonstrated the presence oftwo Tg in commercial non-crosslinked NBR with less than 35% ACN content. Theyconcluded that for PVC/NBR blends containing 70% NBR, PVC acts as selective solventfor only that portion of NBR which is highest in ACN content. Zakrzewski [176] usedphase contrast microscopy, DSC and torsion pendulum analysis to examine thecompatibility of mill-mixed PVC/NBR blends. He concluded that nitrile elastomerscontaining 25%–45% ACN are compatible with PVC at all levels of PVC.

Landi [171, 172, 177] reviewed previous studies on PVC/NBR blends compatibility andused DSC to measure Tg. When a 29% ACN elastomer with two Tg was mixed withPVC, only the higher Tg was affected. Only a nitrile elastomer containing 34% ACNexhibited a single Tg in its PVC blends. Ranby and co-workers [183, 184, 190] examinedtwo properties of mill-mixed PVC/NBR blends with 22–34% ACN using light scattering,

96


gas permeability, density and DMA. Increasing the amount of ACN in the elastomersresulted in better compatibility with PVC.

Wang and Cooper [191] investigated the morphology of PVC/NBR blends spincast fromtetrahydrofuran. Their studies were carried out at various temperatures using DSC, DMA,transmission electron microscopy (TEM) and infrared dichroism technique. Nitrileelastomer containing 44% ACN was found to be incompatible with PVC used underconditions of their blend preparation. Nitrile elastomer containing 31% ACN was foundto be compatible with the PVC with some indications of heterogeneity in form ofmicrodomains which are rich in either PVC or NBR.

Reznikova and co-workers [146, 147, 149, 150] studied the effects of varying the ACNcontent in the nitrile elastomer and the amount of NBR in the compositions, on PVC/NBR blends properties. Nitrile elastomers containing 10%–50% ACN were mill-mixedwith PVC over a range of 0%–100% PVC. Nitrile elastomers containing 28% or lessACN had poor compatibility with PVC giving blends which were cloudy and had weakand poor elasticity. Lel’ckuk and Sedlis [151, 152] studied PVC/NBR blends prepared bylatex blending, followed by coagulation and then milling at 130–140 °C. Nitrile elastomerswith 19%–40% ACN were used. The effect of varying the molecular weight from40,000 to 390,000 of a 35% ACN elastomer was investigated. Nitrile elastomerscontaining 35%–40% ACN with low molecular weight gave the best processability andproperties.

The morphological behaviour of PVC/NBR blends is complex. It appears to be a windowof compatibility whose boundaries are related to ACN content in NBR. The locations ofthe boundaries of this window are not clearly defined. The centre of the window appearsto lie in the region 30%–40% ACN content in the nitrile elastomers [193, 203]. Jorgensen[175] has shown that all commercial non-crosslinked NBR with less than 35% ACNhave two Tg. These correlate with fractions of different ACN content. In the blends withthese copolymers, PVC tends to solubilise the fractions with higher ACN content. Evenin the region near the centre of the window, microheterogeneity in this region may bedue to the multiphase nature of NBR, to the crystallites and residual ‘primary’ particlesof PVC [105, 106, 200–202].

The general PVC/NBR blends properties analysis emphasised that the rubber acts as aplasticiser for PVC and PVC reinforces the rubber. Originally NBR was used as plasticiserfor PVC and PVC was used to improve ozone resistance and weathering of nitrileelastomer. Today, PVC/NBR blends form a class of polymeric materials in their ownright and should be considered as such.

97


When used as thermoplastic materials, the PVC proportion of the blend is frequently50 wt% or above and the properties are nearer those of a plasticised PVC. The nitrileelastomer behaves as a special type of plasticiser, because it is:

1. Non-extractable;

2. Non-migratory;

3. Non-volatile.

Replacement of normal type PVC plasticisers with nitrile rubber gives improved:

1. Oil and solvent resistance;

2. Abrasion resistance;

3. Heat ageing;

4. Brittle temperature;

5. Impact strength;

6. Elongation at break and

7. Retention of mould patterns or embossing [146, 147, 149, 150, 158, 159, 167, 180,181, 187].

Blends intended for use as rubbery type polymers regularly contain a major fraction ofnitrile elastomer and are compounded and crosslinked to give rubbery end products.The most significant advantages obtained by addition of PVC into nitrile elastomer are:

1. It reinforces the rubber;

2. It imparts weathering and ozone resistance;

3. It reduces compound costs.

Compared to a nitrile elastomer a NBR/PVC compound has higher hardness andimproved:

1. Gum strength and modulus;

2. Weather and ozone resistance;

98


3. Solvent and fuel resistance;

4. Abrasion and tear properties;

5. Flame resistance;

6. Volume resistivity;

7. Compound costs [169].

Properties worsened are:

1. Low temperature flexibility;

2. Compression set (particularly at elevated temperatures);

3. Resilience at room temperature.

The extent to which the tracked properties for PVC/NBR blends are achieved is influencedby a great number of factors:

1. PVC/NBR ratio;

2. PVC molecular weight;

3. ACN content in NBR;

4. Nitrile elastomer viscosity;

5. NBR pre-crosslinking degree;

6. Mixing technique;

7. Presence in the system of other additions etc. [167].

Reed [210] stated that nitrile elastomers plasticise PVC by a solvation mechanism in thesame way as monomeric plasticisers. He pointed out that when powdered PVC is addedto NBR and the batch is hot milled, the blend becomes clear and behaves as a normalplasticised compound. The use of nitrile elastomer as a plasticiser resulted in a blendwith excellent resistance to swelling and to loss plasticiser due to extraction and volatility[88]. Increasing levels of ACN will improve the oil resistance but the brittlenesstemperature also increases. The optimum range of addition of plasticised PVC to nitrileelastomers is 20–40 wt% NBR with 29%–39% ACN content [88].

99


Kronman and Karghin [160] found that the impact resistance of PVC was markedlyimproved by low levels of NBR containing 18% ACN. Higher levels of 26 wt%acrylonitrile copolymer were required for comparable improvement and the addition of40 wt% acrylonitrile copolymer had no appreciable effect.

Mann and Williamson [181] stated that a controlled degree of compatibility is requiredfor reinforcement. They also refer to the work of Davenport and co-workers [154] whofound that the impact strength decreased somewhat with an addition of up to 5 phr andthen increased with rubber content.

Kühne [169] established that impact resistance was appreciably greater if the NBR washighly branched and partially crosslinked rather then linear. A suitable modifier was9:1 NBR polymerised to 99% conversion and latex blended with PVC. The optimumparticle size was 0.1–0.3 µm and larger particles were thought to act as notched.

Schwartz and Edwards [182] reported that most of the processing and vulcanisationproperties of compounds based on NBR/PVC blends are affected, often dramatically, byone or more of the fundamental properties of the constituents of the blends, as well as bythe blend ratio.

In the preparation of blends from PVC and NBR there are two very important conditions,which must always be satisfied if the optimum properties are to be obtained. These are:(1) good dispersion of one polymer into the other, and (2) satisfactory fluxing of therubber into the PVC [167].

Nowadays, PVC/NBR blends are prepared by either mechanical compounding in themolten state or mixing NBR latex with emulsion or suspension PVC (followed bycoagulation, fluxing and drying). Furthermore, the blends can either be pre-compoundedor directly blended in the same extruder or moulding machine that is used to form theproduct. However, increasing the degree of fluxing produces tougher, stiffer, blends withhigher melt viscosities, which are more difficult to process.

Mechanical blends of the solid polymers must also be fluxed at higher temperatures (150–160 °C) to cause the complete homogeneity of the two polymers and to obtain the optimumproperties from the blend. A too low temperature will result in underfluxed material withless than optimum properties. Too high a temperature may result in decomposition ofPVC, and possible gellation of the rubber. This results in inconsistency of the product, anddiscoloured, high viscosity materials with a poor processing properties [167].

100


It can be appreciated that the formation of blends of PVC and NMR from solid polymerscan be a difficult process, and certain one that requires very careful control to obtainconsistently good products.

The availability of pre-fluxed blend, i.e., a blend made via a latex blending stage, basedon specially developed polymers, offers many advantages:

1. Excellent processing properties and relatively low viscosity;

2. As the blends are fluxed during manufacture, further high temperature mixing is notrequired;

3. Because of the advantages described in (1) and (2) conventional rubber processingequipment may be used to handle these blends;

4. Homogenous, consistent end-products;

5. Single stock item instead of two, i.e., PVC and NBR;

6. Convenience of polymer from, i.e. thin sheet – easy for handling and weighing or chip– for solution work; automatic weighing systems [167].

When powdered nitrile elastomers became available, they were combined with powderedPVC compounds to make possible the processing of PVC/NBR blends in powder form.The advantages of powder processing are discussed in several publications which showtypical compound formulations useful for thermoplastic applications [171, 172]. Theuse of pre-crosslinked and powdered nitrile elastomer is reported to be effective in reducingthe elastic memory (nerve) of PVC/NBR blends [167].

In the last years, the investigations referring to PVC/NBR blends mainly centred on theirproperty enhancement. With that end in view, they realised and characterised more typesof interpenetrating polymer structures, giving PVC/NBR compositions with substantiallyimproved impact strength, compression set, permanent set, resiliency and high temperatureshape retention [192, 194, 195, 196–200, 203].

Correct compounding of PVC/NBR blends is important, particularly from the point ofview of weathering and ozone resistance. The use of highly reinforcing fillers should beavoided in products that will be used under strained conditions [167].

Because PVC reinforces NBR, a blend has high gum strength. This means that mixingthe blend with fillers such as whiting and clay may produce cheap light colouredcompounds. For cheap black compounds, a similar mixture may be used with the additionof a small amount of carbon black.

101


The use of a small amount of a highly reinforcing filler is permissible together with thecheaper filler or of moderate amount of less reinforcing fillers. In this way, manyspecifications may be matched without the loss of weathering properties. In areas wherethe end product is not going to be used under strained conditions, then highly reinforcingfillers will produce compounds with increased tensile, modulus, tear and abrasion resistance.

Plasticisers for PVC/NBR blends are the ones normally used in nitrile elastomers or PVCto modify viscosity, tensile properties or to improve resilience and low temperatureproperties.

For the compositions based on NBR/PVC, two classes of additives play a significantrole: the vulcanisation agents and those belonging to the protection group, which areintended to provide an increase of end-product resilience. In order to accomplish purethermal destruction, thermooxidative and ozonant protection, one must make allowancesfor both the elastomer part and PVC part protection [182, 188]. Among antidegradantsare suggested diphenylamine derivates, oligomers of dihydroquinoline in combinationwith mercaptobenzimidazole or bis(4-hydroxyphenyl)propionate derivates [106, 179].The protection of some mixtures was accomplished using alkyl-aryl and diaryl derivatesof N,N´-disubstitute p-phenylendiamine, giving good performances until 150 °C [174,181, 189].

The PVC/NBR blends are primarily designed for extrusion and calendering, but injection,blow, compression and transfer moulding are feasible as well. The blends are used inmanufacture of hoses, rolls, wire and cable insulation, footwear, sheets for expandedinsulation, foamed extruded profiles for door and window seals, automotive accessories,diaphragms, conveyor belts, protective clothing, shoe soles, jacketing, roll covers, cableand wire jackets [13, 166].

3.10 PVC/SBR Blends

Although incompatible with PVC, styrene-butadiene statistic copolymers (SBR) arecommonly used to blend with this polymer, to modify impact strength or to obtainthermoplastic elastomers [211, 212]. To enhance PVC miscibility with SBR one canresort to dynamic vulcanisation and/or chemical modification of the elastomer, additionto the blend of micromolecular (anionic tensile active agents [213]) or macromolecular(NBR [214]) compatibilisation agents.

Dynamic vulcanisation of PVC/SBR blends containing or not containing NBR, providesan increase of the adhesion between phases and decrease of particles size dispersed inSBR [214].

102


For PVC/styrene-butadiene-styrene block copolymer (SBS), CPE or acrylic monomergrafted SBS can be used as compatibilisation agent.

The chemical modification of butadiene-styrene copolymers in order to enhance thecompatibility with PVC is often done by epoxidation. For an epoxidated styrene-butadieneblock copolymer (ESB) with 34% degree of epoxidation, it was established that thecompatibility with PVC occurs when the ratio of epoxy functional groups: CHCl is aminimum of 0.5, as in the case of ENR blending.

The blends with epoxy functional groups content less than the minimum required arebiphasic; a phase represents homogeneous blend PVC/ESB and the other PVC [215–217]. SBR star copolymers are less miscible than linear copolymers, because of stericrestrains of epoxidated elastomer segments (miscible in PVC) from nonpolar styrenicsegments.

The most important commercial PVC-based blends are presented in Table 3.1.

103


]812,31[sdnelbCVPlaicremmoC1.3elbaT

dnelB ytilibicsiM reilppusrorerutcafunaM/emanedarT

,EDPL(EP/CVP)EPDH,EPDLL

elbitapmocnI .proCnehciV/nivahtE

EPC/CVP 52nahtsselgniniatnocEPCeraenirolhc%tw

.elbitapmocni%tw54–42gniniatnocEPC

.elbitapmoceraenirolhc

.proCesenaleCtshceoH/ZtilatsoH

yavloS/civneB

AVE/CVP AV%tw08–05htiwAVEmumixamsecudorptnetnoc

.ytilibicsimwolebtnetnocAVhtiwAVE

.elbitapmocnisi%tw05

.cnIetosotnaP/tsalatnaP

sremyloPocenneT/ocenneT

OC-VE/CVP elbitapmoC tnoPuD/nyrclA

MDPE/CVP elbitapmocnI .proClacimehClatnediccO/futyxO

SP/CVP elbitapmocnI slacimehC&knInoppiniaD/aremiL

NAS/CVP elbitapmocniroelbitapmoCtnetnocNAnognidneped

.NASmorf

.oClacimehCatsiV/lerpuSstcudorPremyloPotnasnoM/nartsuL

SBA/CVP noitisopmocnognidnepeD.euqinhcetgniniatbodna

slacimehCcetbA/240nosbAhcirdooGFB

yavloS/civneB.proC.ltnIyollamoC/022yollamoC

scimanyDdecnavdA/A008xudnoCscitsalPEG/yolocyC

.oCnoeGehT/92-KnivocyChcirdooGFB/52-KnivocyChcirdooGFB/BAKnivocyC

ukagaKikneD/SHakneDsussavehC;ukagaKikneD/SCLakneD

ukagaKikneD/nalemiaTakneD&lacimehCahplA/6X/677laruD

scitsalPfluGaigroeG/0322-FH

ihcufaganaK/NxelpnEakenaKslacimehC

Commercial PVC blends

104


deunitnoC1.3elbaT


SBA/CVPdeunitnoC

otomimuS;layorinU/citsalarKcitsalpomrehT.gnEitaL/xelfitsaL

.oClacimehCotnasnoM/SBAnartsuL.tnIcitsalPMSD/yolavraM.oCiesaKnoeZ/LAnoepiN

&scitsalPhcetavoN/0009yollavoNlacimehC

.cnInamuhcS.A/namyloP.cnInamuhcS.A/905,605namyloP

.tnIscitsalPMSD/VyollafnoRsnoS&namuhSspilihP/087namuhS

.oClacimehCdlohieR/etmivuhS.oClacimehCatsiV/AVSlerpuS

;.oClacimehCotnasnoM/EBCxairTGAreyaB

otnasnoM-ihsibustiM/BVxerfurT

SBA/RB/CVP eimehC-niehR/enelirtiN

SBM/CVP elbicsimmI yevloS/civneBsaaHdnamhöR/diolaraP

ASA/CVP elbitapmocnI scitsalPEG/0221YGyoleGscitsalPEG/3002PXyoleG

SAA/CVP elbitapmocnI lacimehCihcatiH/NVnenfiV

/SBA/CVPAMMSMA

noitisopmocnognidnepeD ihcufaganaK/xelpnEakenaKslacimehC

AMMP/CVP elbitapmocniroelbitapmoCfoeergedehtnognidneped

AMMPfoyticitcaton

tnoPuD/EKDsaaHdnamhöR/001xedyK

aissuR/zorpiniV

cilyrca/CVPsyolla

elbitapmocniroelbitapmoCcilyrcanognidneped

tonnetfo(epytremylop)deificeps

.oCrebbuR&eriTlareneG/nivilyrcAeirtsudninebraFGI/nolatsA

nameloDdrahciR/xuldalCEG;ebU;renraW-groB/yoloceD

scitsalPtnoPuD/EKD

.proCakenaK/xelpnE.oCnoeGehT/XTHcalrebiF


105


deunitnoC1.3elbaT


cilyrca/CVPsyolla

deunitnoC

noeZnoppiN/nelubiaHtshceöH/MH,HtilatsoH

slacimehCihcufaganaK/ecA-enaKsaaHdnamhöR/enedyK

saaHdnamhöR/001xedyKnoyaRihsibustiM/nelubateM

etilayoR/tsacyloPscitsalPakanustusT/DKdiolanuS

eirtsudninebraFGI/diolulorTeirtsudninebraFGI/rudivorT

scitsalPFSAB/rudiniV

htiwsyollaCVPedimiratulg

cilyrcaremylopoc

elbicsiM fluGaigroeG/10raelCyrutneC-rosyeK/721CK

&scitsalPhcetavoN/dnelbavoNlacimehC

lacimehClatnediccO/0914raelcyxO.proC

syollaCVP elbitapmoC .proClacimehClatnediccO/dnelbyxO.proCmehciV/nivirT

cAVP/CVP elbitapmocnI .cnIremyloP/dnertsirB

FVP/CVP hcirdooGFB/laesoroK

UPT/CVP .cnIlacimehCdlohcieR/enatuhS

RBN/CVP NA%03wolebhtiwRBNhtiwRBNelbitapmocniera

eraNA%54–%03elbitapmoc

yevloS/civneB.cnIlacimehCyraC/yolraC

&eriTraeydooG/EPT/nugimehC.oCrebbuR

sussavehC;ukagaKikneD/SCLakneDhcirdooGFBnoeG

hcirdooGFB/racyN/noeGhcirdooGFB/racyH

rebbuRcitehtnySnappaJ/VNRSJreyaB;.cnIseliM;rasyloP/VNcanyrK

GA.dtL.oCnoeZnoppiN/lopiN


106


References

1. J.A. Brydson, Plastics Materials, 5th Edition, Butterworths, London, UK, 1989.

2. J. Frissell in Encyclopaedia of PVC, Ed., L.I. Nass, Marcel Dekker, Inc., NewYork, NY, USA, 1976, 1, 258.

deunitnoC1.3elbaT


RBN/CVPdeunitnoC

.oCnoeZnopiN/remylopreTlopiN.dtL

.proCmehciV/nivortiNmehcyxO/dnelbyxO

.oClacimehClayorinU/OZAlyrcaraP.cnI

.oClacimehClayorinU/OZOlyrcaraP.cnI

sremyloPocenneT/ocenneTscitsalPdnaslacimehCahplA/etinyV

.proCretxeD

remotsale/CVP remotsalenognidnepeD)deificepston(erutan

.cnIslacimehCyraC/yolraCseliM;GAreyaB/009CEdnelborkaM

.cnI.proClacimehClatnediccO/dnelbyxO

.A;iesaKihsibustiM/enerpnuS.cnInamuhS

.cnInamuhS.A/akiniV

RB/CVP slacimehCsdnarBdradnatS/calyT

RBA/CVP .mehCdlohcieR/etinivuhS

RBN/UPT/CVP scitsalP&lacimehCahplA/xelaruD

rebbureneidatuB:RBremylopoceneryts-)retse(etalyrca-elirtinolyrcA:SAA

rebbureneidatub-)retse(etalyrcA:RBAediroulflynivyloP:FVP

enahteruylopcitsalpomrehT:UPT:AMMSMA α remylopocetalyrcahtemlyhtem-enerytslyhtem-


107


3. Polymer Data Handbook, Ed., J.E. Mark, Oxford University Press, Oxford, UK,1999.

4. J.C. Huang, D.C. Chang and R.D. Deanin, Advances in Polymer Technology,1993, 12, 1, 81.

5. R.D. Deanin and C.H. Chung in Handbook of Polyolefins: Synthesis andProperties, Eds., C. Vasile and R.B. Seymour, Marcel Dekker, Inc., New York,NY, USA, 1993, 779.

6. D.R. Paul in Polymer Blends, Eds., R.D. Paul and S. Newman, Academic Press,New York, NY, USA, 1978, 2, 35.

7. H. Ling and B.D. Favis, Industrial Engineering & Chemistry Research, 1997, 36,1211.

8. A. Tripathi, H.K. Tripathi and P.C.K. Rallai, Journal of Applied Physics, 1988,64, 4, 2081.

9. R. Mikkoian and A. Savoleinen, Journal of Applied Polymer Science, 1990, 39,8, 1709.

10. Y. Nakamura, Polymeric Materials: Science and Engineering, 1987, 57, 775.

11. Y. Nakamura, A. Watanabe, K. Mori, K. Tomura and H. Niyazaki, Journal ofPolymer Science, Part C: Polymer Letters, 1987, 25, 3, 127.

12. A. Rudin and P. van Ballegooie, Journal of Applied Polymer Science, 1990, 39,10, 2097.

13. L.A. Utracki, Commercial Polymer Blends, Chapman and Hall, London, UK, 1998.

14. J. Zalinger, Journal of Polymer Science, 1969, C16, 4259.

15. Y.J. Shurand and B. Ranby, Journal of Applied Polymer Science, 1976, 20, 3105.

16. J.J. del Val, C. Lacabanne and A. Hiltner, Journal of Applied Physics, 1988, 63,5312.

17. A. Tse, R. Laakso, E. Baer and A. Hiltner, Journal of Applied Polymer Science,1991, 42, 1205.

18. S. Stroeva, P. Kartalov and K. Jankova, Journal of Polymer Science: Part BPolymer Physics, 1998, 36, 1595.

108


19. X. Xu, L. Zang and H. Li, Polymer Engineering and Science, 1987, 27, 398.

20. M.F. Champagne and R.E. Prud’homme, Journal of Polymer Science: Part BPolymer Physics, 1994, 34, 615.

21. G.F. Ignatova, V.L. Trizno, A.F. Nicolaev and N.V. Daniel, Plasticheskie Massy(USSR), 1994, 31, 1, 136.

22. H. Xi, Z. Liwn and L. Huilin, Polymer Engineering and Science, 1987, 27, 2,328.

23. M. Rusu, M.D. Bucevschi, F. Petraru and L. Gramescu, Iranian Journal ofPolymer Science and Technology, 1995, 3, 2, 121.

24. M. Rusu, M.D. Bucevschi, F. Petraru and L. Gramescu, Iranian Journal ofPolymer Science and Technology, 1996, 4, 1, 64.

25. N. Yamada, S. Shoji, H. Sasuhi, A. Nagatani, K. Yamaguchi, S. Kahjiva and A.S.Hashim, Journal of Applied Polymer Science, 1999, 71, 855.

26. N.S. Koklas, D.D. Sotiropouloer, J.K. Kollitsis and N.K. Kolfoglu, Polymer,1991, 32, 1, 26.

27. C.F. Hammer, Macromolecules, 1971, 4, 1, 69.

28. D. Feldman and M. Rusu, European Polymer Journal, 1974, 10, 1, 41.

29. C. Elmqvist and S.E. Svanson, Kolloid – Zeitschrift und Zeitschrift fur Polymere,1975, 253, 327.

30. C. Elmqvist and S.E. Svanson, European Polymer Journal, 1975, 11, 789.

31. J. Shur and B. Ranby, Journal of Applied Polymer Science, 1975, 19, 5, 1337.

32. B.G. Ranbt, Journal of Polymer Science: Symposium, 1975, 51, 1973.

33. C. Elmqvist and B. Ranby, European Polymer Journal, 1976, 12, 559.

34. J. Zelinger, V. Heidingsfeld and V. Altman, Plasty a Kaucuk, 1976, 7, 131.

35. E. Nolley, D.R. Paul and J.W. Barlow, Journal of Applied Polymer Science, 1979,23, 623.

36. R.D. Deanin and N.A. Shah, Journal of Vinyl Technology, 1983, 4, 2, 167.

109


37. C.A. Cruz-Ramas and R.D. Paul, Macromolecules, 1989, 22, 1289.

38. R.D. Deanin and N.A. Shah, Organic Coatings and Plastics Chemistry, 1981, 45,2, 290.

39. G. F. Hofman, R.J. Statz and R.B. Case, Journal of Vinyl Technology, 1994, 16,1, 16.

40. J.A. Wingrave, Journal of Vinyl Technology, 1980, 2, 2, 204.

41. J.J. Hickman and R.M. Ikeda, Journal of Polymer Science, Part A2, 1973, 11,1713.

42. R.D. Paul, C.E. Viston and C.E. Locke, Polymer Engineering and Science, 1972,12, 157.



45. M. Rusu, Materiale Plastice, 1982, 19, 4, 231.

46. L.G. Boulard and D. Brountstein, Journal of Applied Polymer Science, 1986, 32,6131.

47. A. Danit and D.P. Dehponde, Polymer Science, 1994, 2, 692.

48. J.S. Orville, The Science and Technology of Polymer Films, Wiley, New York,NY, USA, 1971, 2.

49. Y. Haiyang, Z.P. Pingping, L. Guofen, W. Peng and R. Feng, Polymer Journal,1999, 35, 345.

50. T. Hayashi, J. Ito, K. Mitani and Y. Mizutani, Journal of Applied PolymerScience, 1987, 33, 375.

51. J. Heushen, J.M. Vion, R.Y. Jerome and P. Teyssie, Polymer, 1990, 31, 1473.

52. G.T. Carreba and S. Kandiraju, Advances in Polymer Technology, 1990, 10, 237.

53. J.K. Kallitsis and N.K. Kalfoglou, Polymer, 1989, 30, 2258.

110


54. T.P. Russel, A.M. Mayers, V.R. Daline and T.C. Chung, Macromolecules, 1992,25, 5783.

55. B. Boutevin, Y. Pietrosonta, J.J. Robin and T. Pallat, European Polymer Journal,1988, 24, 953.

56. D. Braun, M. Fisher and G.P. Hellman, Die Makromolekulare Chemie –Macromolecular Symposia, 1994, 83, 77.

57. M. Rink, L. Monfrini, P. Gasparini and A. Paven, Plastics and Rubber Processingand Applications, 1983, 3, 2, 145

58. R.Y. Jerome, B. Albert and P. Teyssie, Polymer Preprints, 1986, 27, 1, 72.

59. A. Rudin, S. Bloembergen and S. Cork, Journal of Vinyl Technology, 1985, 7, 1,103.

60. D. Braun, B. Böhringer, N. Eidam, M. Fischer and S. Krömerling, AngewandteMakromolekulare Chemie, 1994, 216, 1.

61. K. Kuzelova and Z. Vymazol, European Polymer Journal, 1999, 35, 351.

62. J.G. Bryner, Journal of Vinyl Technology, 1990, 12, 2, 105.

63. A.K. Kulshreshtha, B.P. Sing and Y.N. Sharma, European Polymer Journal, 1988,24, 1, 33.



66. D.M. Fann, H.Y. Shih, C.M. Hsiao and S.K. Huang, Journal of Vinyl Technology,1989, 11, 129.

67. S. Hawriliak and T.J. Shortridge, Journal of Polymer Science: Part B PolymerPhysics, 1990, 28, 1987.

68. L.A. Utrachi, International Polymer Processing, 1987, 2, 1, 1.

69. W.J. Casey and K. Okano, Journal of Vinyl Technology, 1986, 1, 1, 37.

70. K. Yamamoto, T. Maehala, K. Mitani and Y. Mizutani, Journal of AppliedPolymer Science, 1993, 50, 753.

111


71. K. Yamamoto, T. Maehala, K. Mitani and Y. Mizutani, Journal of AppliedPolymer Science, 1994, 51, 755.

72. E. Linder, E Graf, Z. Niegreisz, K. Toth, E. Pungor and R.P. Buch, AnalyticalChemistry, 1988, 60, 295.

73. J. Anzai and C.C. Li, Polymer Communications, 1999, 31, 10, 375.

74. P.R. Babu and V.G. Gaikar, Journal of Applied Polymer Science, 1999, 73, 1117.

75. D.E. Bhagwager, C.I. Serman, P.C. Painter and M.M. Coleman, Macromolecules,1989, 22, 4654.

76. H. de Jager and G. ten Brinke, Macromolecules, 1991, 24, 3454.

77. C. Vasile, A. Stoleru, M. Esanu and G. Adamescu, Materiale Plastice, 1990, 27,3, 117.

78. C. Vasile and I.A. Schneider, European Polymer Journal, 1971, 7, 1205.

79. M. Sabliovschi and G. Grigoriu, Journal of Thermal Analysis, 1983, 26, 1, 23.

80. I.C. McNeill and A. Jamieson, Journal of Polymer Science, Part A: PolymerChemistry Edition, 1974, 12, 387.

81. S.H. Goh, Thermochimica Acta, 1993, 215, 291.

82. R.E. Prud’homme, Polymer Engineering and Science, 1982, 22, 1138.

83. S. Lee, J.G. Lee, H. Lee and S.J. Mumby, Polymer, 1999, 40, 5137.

84. M.M. Coleman, C.I. Serman, D.E. Bhagwager and P.C. Painter, Polymer, 1990,31, 1187.

85. B.R. Riedl and R.E. Prud’homme, Journal of Polymer Science: Part B PolymerPhysics, 1986, 24, 2565.

86. R.S. Stein, A. Mirva, T. Yuasa and F.B. Khambatta, Pure and Applied Chemistry,1977, 49, 915.

87. J.V. Kaleske in Polymer Blends, Eds., D.R. Paul and S. Newman, Academic Press,New York, NY, USA, 1978, 369.

88. O. Olabisi, L.M. Robeson and M.T. Shaw, Polymer-Polymer Miscibility,Academic Press, New York, NY, USA, 1979.

112


89. P.T. Gilmore, R. Falabella and R.L. Laurence, Macromolecules, 1980, 13, 4, 880.

90. M. Abutin and R.E. Prud’homme, Macromolecules, 1988, 21, 2941.

91. P. Zhy, H. Yang and S. Wang, European Polymer Journal, 1998, 34, 1, 91.

92. H. Yang, P. Zhy, S. Wang and Q. Guo, European Polymer Journal, 1998, 34, 3/4,91.

93. H. Yang, P. Zhy, S. Wang and Q. Guo, European Polymer Journal, 1998, 34, 9,1303.

94. D. Keroack, Y. Zhao and R.E. Prud’homme, Polymer, 1999, 40, 243.

95. H.L. Chen, J.L. Li and T.L. Lin, Macromolecules, 1998, 31, 2255.

96. D. Ma, H. Cai, J. Zang and X. Liaolie, Macromolecular Chemistry and Physics,1999, 200, 2040.

97. J.R. Runt and P.B. Rim, Macromolecules, 1983, 16, 762.

98. S. Nojima and A. Peterlin, Journal of Polymer Science, Part A2, 1971, 9, 1191.

99. C.F. Hammer in Polymer Blends, Eds., D.R. Paul and S. Newman, AcademicPress, New York, NY, USA, 1978, 2.

100. I.C. McNeill and L.T. Memetea, Polymer Degradation and Stability, 1991, 33,263.

101. I.C. McNeill and S. Basan, Polymer Degradation and Stability, 1993, 41, 311.

102. D.J. Hourston and D.I. Hughes, Journal of Applied Polymer Science, 1977, 21,3099.

103. D.J. Hourston and D.I. Hughes, Polymer, 1979, 20, 829.

104. T. Nishi, T.K. Kwei and T.T. Wang, Journal of Applied Physics, 1975, 46, 4157.

105. S-Y. Kwak, Polymer Journal (Japan), 1994, 26, 4, 491.

106. N. Nakajima and S.Y. Kwak, International Polymer Processing, 1995, 10, 1, 1.

107. I.H. Park, J.S. Jang and Y. Chujo, Angewandte Makromolecular Chemie, 1995,226, 1.

113


108. D.Z. Ma and R.E. Prud’homme, Polymer, 1990, 31, 917.

109. T. Nishi and T.K. Kwei, Journal of Applied Polymer Science, 1976, 20, 1331.

110. L.M. Robeson, Journal of Polymer Science, Part A: Polymer Letters, 1978, 16, 261.

111. D.J. Hourston and I.D. Hughes, Journal of Applied Polymer Science, 1977, 21,3093.

112. R.P. Kane, Journal of Elastomers and Plastics, 1977, 9, 416.

113. P. Penczek and G. Cynkowoska, International Polymer Science and Technology,1977, 4, 5, 19.

114. S. Krause in Polymer Blends, Eds., D.R. Paul and S. Newman, Academic Press,New York, NY, USA, 1978, 1.

115. M.M. Gorelova, A.J. Pertsin, V.Y. Levin, L.I. Makarova and L.V. Filimonova,Journal of Applied Polymer Science, 1992, 45, 2075.

116. V.S. Papkov, G.G. Nikiforova, I.M. Raygorodsky and I.P. Storozlurk,Vyskomolekulyarnye Soedineniya, Series B, 1975, 37, 428.

117. V.S. Papkov, G.G. Nikiforova, V.G. Nikal’ski, I.A. Krasotkin andE.S.Obolonkova, Polymer, 1998, 39, 3, 631.

118. W.H. Jo and I.H. Kwon, Macromolecules, 1991, 24, 3368.

119. C. Marco, M.A. Gómez, J.G. Fatou, A. Etxeberria, M.M. Elorza and J.J. Iruin,European Polymer Journal, 1993, 29, 11, 1477.

120. A.G. Margaritis and N.K. Kalfoglou, Journal of Polymer Science: Part B PolymerPhysics, 1988, 26, 1595.

121. A.G. Margaritis and N.K. Kalfoglou, Journal of Polymer Science: Part B PolymerPhysics, 1989, 27, 1767.

122. Y.Z. Meng and S.C. Tjong, Polymer, 1999, 40, 2711.

123. J. Zelinger and V. Heidingsfeld, Sbornik Vysoke Skoly Chemicko-TechnologickePraze, 1996, 9, 63.

124. D. Feldman and M. Rusu, European Polymer Journal, 1971, 7, 2, 215.

114


125. N.K. Naqvi and A.N. Sen, Polymer Degradation and Stability, 1991, 93, 367.

126. E.V. Kolawale and P.O. Olugbeni, European Polymer Journal, 1985, 21, 8, 187.

127. Y. Zhang, Y. Yong, S. Han, X. Zhang and C. Yang, Polymer-PolymerCompositions, 1994, 2, 3, 1981.

128. I.R. Gelling and M. Porter in Natural Rubber Science and Technology, Ed., A.D.Roberts, Oxford University Press, Oxford, UK, 1988.

129. A.G. Margaritis, J.K. Kallitsis and N.K. Kalfoglou, Journal of Applied PolymerScience, 1986, 32, 2867.

130. A.G. Margaritis and N.K. Kalfoglou, European Polymer Journal, 1988, 24,1043.

131. K.T. Varughese, G.B. Nando, P.P. De and S.K. De, Journal of Materials Science,1988, 23, 3894.

132. K.T. Varughese, P.P. De, S.K. Sanyal and S.K. De, Journal of Applied PolymerScience, 1989, 37, 2537.

133. U.S. Ishiaku, M. Nasir and Z.A.M. Ishak, Journal of Vinyl Technology, 1994, 16,219.

134. U.S. Ishiaku, M. Nasir and Z.A.M. Ishak, Journal of Vinyl Technology, 1994, 16,226.

135. K.T. Varughese, P.P. De, G.B. Nando and S.K. De, Journal of Vinyl Technology,1987, 9, 161.

136. U.S. Ishiaku and Z.A.M. Ishak in Polymer Blends and Alloys, Eds., G.O.Shanaike and G.P. Simon, Marcel Dekker, Inc., New York, NY, USA, 1999, 663.

137. U.S. Ishiaku, M. Nasir and Z.A.M. Ishak, Journal of Vinyl Additive Technology,1995, 1, 142.

138. Z.A. Nasir and C.T. Ratnam, Journal of Applied Polymer Science, 1989, 38,1219.

139. L.A. Utracki, Polymer Engineering and Science, 1982, 22, 1166.

140. S.N. Koklas, D.D. Sotiropoulou, K.K. Kallitsis and N.K. Kalfoglou, Polymer,1991, 32, 66.

115


141. N. Yamada, S. Shoji, H. Saski, A. Nagatami, K. Yamaguchi, S. Kohjiya and A.S.Hashima, Journal of Applied Polymer Science, 1999, 71, 855.

142. T. Iida, J. Kawato, K. Murayama and K. Goto, Journal of Applied PolymerScience, 1987, 34, 2355.

143. T. Iida, J. Kawato, S. Tanie and K. Goto, Journal of Applied Polymer Science,1989, 37, 1685.

144. A. Emmet, Industrial & Engineering Chemistry, 1944, 36, 730.

145. L.E. Nielsen, Journal of the American Chemical Society, 1953, 75, 1435.

146. R.A. Reznikova, A.D. Zaionchkovsky and S.S. Voyutsky, Kolloidnyi Zhurnal,1953, 15, 111.

147. R.A. Reznikova, S.S. Voyutsky and A.D. Zaionchkovsky, Kolloidnyi Zhurnal,1954, 16, 207.

148. W. Breuers, W. Hild, H. Wolf, W. Burmeister and E. Hoyer, Plaste undKautschuk, 1954, 1, 2, 170.

149. R.A. Reznikova, A.D. Zaionchkovsky and S.S. Voyutsky, Zhurnal TeknicheskoiFiziki, 1955, 25, 6, 1045.

150. S.S. Voyutsky, A.D. Zaionchkovsky and R.A. Reznikova, Kolloidnyi Zhurnal,1956, 18, 511.

151. S.L. Lel’chuk and V.I. Sedlis, Zhurnal Prikladnoi Khimii, 1957, 30, 1041.

152. S.L. Lel’chuk and V.I. Sedlis, Zhurnal Prikladnoi Khimii, 1958, 31, 790.

153. N.E.Devenport, L.W. Hubbard and N.P. Pettit, British Plastics, 1959, 32, 12,549.

154. L.E. Nielson, Mechanical Properties of Polymers, Reinhold PublishingCorporation, New York, NY, USA, 1962.

155. M. Takayanagi, H. Harima and Y. Iwatu, Memoirs of the Faculty of Engineering,Kyushu Imperial University, 1963, 23, 1.

156. M. Takayanagi, H. Harima and Y. Iwatu, Journal of the Japanese Society ofMaterials Testing, 1963, 12, 389.

116


157. W. Rovatti and E. Bobalek, Journal of Applied Polymer Science, 1963, 7, 6,2269.

158. M. Iamoto, Y. Minoura, K. Goto, A. Yabe, M. Takimya, I. Ando, Y. Ymakura, H.Kenbishi, S. Yabuta, T. Hidaka, K. Komuro, H. Tahara, M. Shundo and K. Mega,Nippon Gomu Kyokaishi, 1965, 38, 482.

159. M. Iamoto, Y. Minoura, K. Goto, A. Yabe, M. Takimya, I. Ando, Y. Ymakura, H.Kenbishi, S. Yabuta, T. Hidaka, K. Komuro, H. Tahara, M. Shundo and K. Mega,Nippon Gomu Kyokaishi, 1965, 38, 657.

160. A.G. Kronman and V.Karghin, Vyskomolekulyarnye Soedineniya, Series A, 1966,8, 1874.

161. M. Matsuo, Japanese Plastics, 1968, 2, 6.

162. L. Bohn, Rubber Chemistry and Technology, 1968, 41, 495.

163. S. Manabe, R. Murakami and M. Takayanagi, Memoirs of the Faculty ofEngineering, Kyushu Imperial University, 1969, 28, 295.

164. Y.G. Oganesov, V.S. Ospchiuk, K.G. Mindyarov, V.G. Rayevsky and S.S.Voyntski, Vyskomolekulyarnye Soedineniya, Series A, 1969, 11, 4, 896.

165. M. Matsuo, C. Nozaki and Y. Jyo, Polymer Engineering and Science, 1969, 9, 197.

166. D. Feldman and M. Rusu, European Polymer Journal, 1970, 6, 627.

167. K.A. Pedley, Polymer Age, 1970, 1, 3, 97.

168. D. Feldman and M. Rusu, Revue Generale des Caoutchoucs et Plastiques, 1971,48, 6, 687.

169. G.F. Kühne, SPE Technical Papers, 1971, 17, 491.

170. S. Krause, Journal of Macromolecular Science – Reviews in MacromolecularChemistry, 1972, C7, 2, 251.

171. V. Landi, Rubber Chemistry and Technology, 1972, 45, 222.

172. V. Landi, Rubber Chemistry and Technology, 1972, 45, 1684.

173. R.D. DeMarco, M.E. Woods and L.F. Arnold, Rubber Chemistry andTechnology, 1972, 45, 1111.

117


174. I. Fetterman, Rubber Chemistry and Technology, 1972, 46, 4, 927.

175. A.H. Jorgensen, A.L. Chandler and E.A. Collins, Rubber Chemistry andTechnology, 1973, 46, 1087.

176. G.A. Zakrzewski, Polymer, 1973, 14, 347.

177. V. R. Landi, Applied Polymer Symposia, 1974, 25, 223.

178. D. Feldman and M. Rusu, Plaste und Kautschuk, 1973, 20, 4, 259.

179. M.H. Abbelkader and S.M. Yussif, Plaste und Kautschuk, 1974, 21, 3, 521.

180. P.J. Corish and B.D.W. Powell, Rubber Chemistry and Technology, 1974, 47, 3, 481.

181. J. Mann and R. Williamson in Physics of Glassy Polymers, Ed., N.R. Haward,John Wiley & Sons, New York, NY, USA, 1973, Chapter 8.

182. H.F. Schwartz and W.S. Edwards, Applied Polymer Symposia, 1974, 25, 243.

183. B.G. Ranby, Journal of Polymer Science: Polymer Symposia, 1975, 51, 89.

184. Y.J. Shur and B.G. Ranby, Journal of Applied Polymer Science, 1975, 19, 2143.

185. P.H. Geil, Industrial Engineering Chemistry Product Research Development,1975, 14, 59.

186. J.R. Dunn, Rubber Chemistry and Technology, 1976, 49, 4, 978.

187. J.R. Dunn, D.C. Coulthard and H.A. Pfisterer, Rubber Chemistry andTechnology, 1978, 61, 389.

188. J.R. Dunn, H.A. Pfisterer and J.J. Ridhend, Rubber Chemistry and Technology,1979, 52, 2, 331.

189. P.H. McKinstay, International Plastic and Rubber, 1980, 30, 1, 10.

190. B. Terselius and B.G. Ranby, Pure and Applied Chemistry, 1981, 53, 421.

191. C.B. Wang and S.L. Cooper, Journal of Polymer Science: Part B Polymer Physics,1983, 21, 11.

192. K.E. George, R. Joseph and D.J. Francis, Journal of Applied Polymer Science,1986, 32, 2867.

118


193. J.R. Wolfe Jr., in Thermoplastic Elastomers, A Comprehensive Review, Eds., N.R.Legge, G. Holden and H.E. Schroeder, Hanser Publishers, Munich, Germany,1987, 117.

194. G. Ivan, E. Bugan, R. Plesa and P. Bujenita, Industrie Usoara (Bucharest), 1988,35, 2, 64.

195. P. Ramesh and S.K. De, Polymer Communications, 1990, 31, 466.

196. C. Vasile, M. Badea, E. Costea, G. Adamescu, A. Caileanu and S. Ioan, MaterialePlastice, 1990, 27, 4, 199.

197. M. Kozlowski, V. Duchacek and A. Kuta, Polimery TworzywaWielkoczasteczkowe, 1991, 36, 5, 181.

198. K. Fukumori, N. Sato and T. Kurauchi, Rubber Chemistry and Technology, 1991,64, 4, 522.

199. C. Vasile, A. Stoleru, E. Costea and M. Sava, Bulletin of the Polytechnic Instituteof Iasi, Section II, 1992, 36, 1-2, 75.

200. A. Mathew, B.C. Charobathy and P.C. Deb, Journal of Applied Polymer Science,1994, 53, 8, 1107.

201. N. Nakajima and S.Y. Kwak, Journal of Macromolecular Science Part B: Physics,1995, 34, 1-2, 137.

202. S.Y. Kwak and N. Nakajima, Journal of Macromolecular Science Part B: Physics,1995, 34, 1-2, 153.

203. M. Giugiuca and G. Ivan, Materiale Plastice, 1995, 32, 3-4, 217.

204. B.E. Krisyuk, A.A. Popov, N.M. Livanova and A.P. Farmakovskaya,Vyskomolekulyarnye Soedineniya, Series A, 1999, 41, 1, 102.

205. D.C. Andrei and C. Andrei, Materiale Plastice, 1990, 27, 1, 23.

206. D.C. Andrei and C. Andrei, Materiale Plastice, 1990, 27, 2, 79.

207. M. Rusu and D. Feldman, Materiale Plastice, 1972, 9, 4, 175.

208. M. Rusu and D. Feldman, Materiale Plastice, 1972, 9, 10, 521.

119


209. C. Vasile, M. Badea, E. Costea, G. Adamescu, A. Stoleru, A. Caileanu and G.Ioanid, Materiale Plastice, 1991, 28, 1-2, 30.

210. M.C. Reed, Modern Plastics, 1949, 27, 12, 117.

211. P. Zhou and Z. Sun, Polymer, 1986, 27, 1899.

212. P. Zhou and Z. Sun, Plastics and Rubber Processing and Applications, 1987, 7,229.

213. Z. Sun and B. Ling, Polymer Preprints, 1987, 28, 2, 54.

214. S. Sha, T. Zhang and Z. Xie, Xiangjao Gongye, 1992, 40, 15, 297.

215. A. G. Mongavitis, I.K. Kollitsis and N.K. Kalfoglou, Polymer, 1989, 30, 2, 2253.

216. S.N. Koklas and N.K. Kalfoglou, Polymer, 1992, 33, 1, 75.

217. S.N. Koklas, N.G. Gavralas and N.K. Kalfoglou, Polymer, 1994, 35, 7, 1425.

218. L.A. Utracki, Polymer Alloys and Blends, Thermodynamics and Rheology,Hanser Publishers, Munich, Germany, 1989.

View publication statsView publication stats

https://www.researchgate.net/publication/236132890

polyvinyl chloride-based blends

Documents