polymer and composite materials study materials

8/12/2019 Polymer and Composite Materials Study Materials

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MF 9260 POLYMER AND COMPOSITE MATERIALS

UNIT 1 PROPERTIES OF POLYMERS

POLYMER CHEMISTRY

Polymer chemistry or macromolecular chemistry is a multidisciplinary science that deals withthe chemical synthesis and chemical properties of polymers or macromolecules. According to IUPACrecommendations, macromolecules refer to the individual molecular chains and are the domain ofchemistry. Polymers describe the bulk properties of polymer materials and belong to the field of polymer

physics as a subfield of physics.

Polymer chemistry is that branch of one, which deals with the study of synthesis and properties ofmacromolecules.

Biopolymers produced by living organisms:o structural proteins: collagen, keratin, elastin o chemically functional proteins: enzymes, hormones, transport proteins o structural polysaccharides: cellulose, chitin o storage polysaccharides: starch, glycogen o nucleic acids: DNA, RNA

Synthetic polymers used for plastics fibers, paints, building materials, furniture, mechanical parts, adhesives:

o thermoplastics: polyethylene, Teflon, polystyrene, polypropylene, polyester, polyurethane, polymethyl methacrylate, polyvinyl chloride, nylon, rayon, celluloid, silicone

o thermosetting plastics: vulcanized rubber, Bakelite, Kevlar, epoxy

Polymers are formed by polymerization of monomers. A polymer is chemically described by itsdegree of polymerisation, molar mass distribution, tacticity, copolymer distribution, the degree of

branching, by its end-groups, crosslinks, crystallinity and thermal properties such as its glass transitiontemperature and melting temperature. Polymers in solution have special characteristics with respect tosolubility, viscosity and gelation.

CLASSIFICATION OF POLYMERS:

Polymers may be classified as follows, according to the mechanical response at elevated temperatures

1. Thermoplasts2. Thermosets

THERMOPLASTS:

Thermoset polymers soften when heated and harden when cooled. Simultaneous application ofheat and pressure is required to fabricate these materials.

On the molecular level, when the temperature is raised, secondary bonding forces are diminishedso that the relative movement of adjacent chains is facilitated when a stress is applied.
http://en.wikipedia.org/wiki/Sciencehttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Macromoleculehttp://en.wikipedia.org/wiki/IUPAChttp://en.wikipedia.org/wiki/Chemistryhttp://en.wikipedia.org/wiki/Polymer_physicshttp://en.wikipedia.org/wiki/Polymer_physicshttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Biopolymerhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Collagenhttp://en.wikipedia.org/wiki/Keratinhttp://en.wikipedia.org/wiki/Elastinhttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Hormonehttp://en.wikipedia.org/wiki/Transport_proteinhttp://en.wikipedia.org/wiki/Polysaccharidehttp://en.wikipedia.org/wiki/Cellulosehttp://en.wikipedia.org/wiki/Chitinhttp://en.wikipedia.org/wiki/Starchhttp://en.wikipedia.org/wiki/Glycogenhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Fiberhttp://en.wikipedia.org/wiki/Painthttp://en.wikipedia.org/wiki/Building_materialhttp://en.wikipedia.org/wiki/Furniturehttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Adhesivehttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wikipedia.org/wiki/Polyethylenehttp://en.wikipedia.org/wiki/Teflonhttp://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Polyurethanehttp://en.wikipedia.org/wiki/Polymethyl_methacrylatehttp://en.wikipedia.org/wiki/Polyvinyl_chloridehttp://en.wikipedia.org/wiki/Nylonhttp://en.wikipedia.org/wiki/Rayonhttp://en.wikipedia.org/wiki/Celluloidhttp://en.wikipedia.org/wiki/Siliconehttp://en.wikipedia.org/wiki/Thermosetting_plastichttp://en.wikipedia.org/wiki/Vulcanizationhttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Bakelitehttp://en.wikipedia.org/wiki/Kevlarhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Polymerizationhttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Degree_of_polymerisationhttp://en.wikipedia.org/wiki/Molar_mass_distributionhttp://en.wikipedia.org/wiki/Tacticityhttp://en.wikipedia.org/wiki/Copolymerhttp://en.wikipedia.org/wiki/Branching_%28chemistry%29http://en.wikipedia.org/wiki/End-grouphttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Crystallinityhttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Solubilityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Gelhttp://en.wikipedia.org/wiki/Gelhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Solubilityhttp://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Crystallinityhttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/End-grouphttp://en.wikipedia.org/wiki/Branching_%28chemistry%29http://en.wikipedia.org/wiki/Copolymerhttp://en.wikipedia.org/wiki/Tacticityhttp://en.wikipedia.org/wiki/Molar_mass_distributionhttp://en.wikipedia.org/wiki/Degree_of_polymerisationhttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Polymerizationhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Kevlarhttp://en.wikipedia.org/wiki/Bakelitehttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Vulcanizationhttp://en.wikipedia.org/wiki/Thermosetting_plastichttp://en.wikipedia.org/wiki/Siliconehttp://en.wikipedia.org/wiki/Celluloidhttp://en.wikipedia.org/wiki/Rayonhttp://en.wikipedia.org/wiki/Nylonhttp://en.wikipedia.org/wiki/Polyvinyl_chloridehttp://en.wikipedia.org/wiki/Polymethyl_methacrylatehttp://en.wikipedia.org/wiki/Polyurethanehttp://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Teflonhttp://en.wikipedia.org/wiki/Polyethylenehttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wikipedia.org/wiki/Adhesivehttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Furniturehttp://en.wikipedia.org/wiki/Building_materialhttp://en.wikipedia.org/wiki/Painthttp://en.wikipedia.org/wiki/Fiberhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Glycogenhttp://en.wikipedia.org/wiki/Starchhttp://en.wikipedia.org/wiki/Chitinhttp://en.wikipedia.org/wiki/Cellulosehttp://en.wikipedia.org/wiki/Polysaccharidehttp://en.wikipedia.org/wiki/Transport_proteinhttp://en.wikipedia.org/wiki/Hormonehttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Chemical_reactionhttp://en.wikipedia.org/wiki/Elastinhttp://en.wikipedia.org/wiki/Keratinhttp://en.wikipedia.org/wiki/Collagenhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Biopolymerhttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Polymer_physicshttp://en.wikipedia.org/wiki/Polymer_physicshttp://en.wikipedia.org/wiki/Chemistryhttp://en.wikipedia.org/wiki/IUPAChttp://en.wikipedia.org/wiki/Macromoleculehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Science


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Most Linear polymers and those having branched structures with flexible chains arethermoplastics.

Thermoplastics are very soft and ductile.

The commercial available thermoplasts are

Polyvinyl Chloride (PVC) and Polystyrene Polymethyl methacrylate Polystyrene

B) Thermosets:

Thermosetting polymers become soft during their first heating and become permanently hardwhen cooled. They do not soften during subsequent heating. Hence, they cannot beremolded/reshaped by subsequent heating.

In thermosets, during the initial heating, covalent cross-links are formed between adjacentmolecular chain. These bonds anchor the chains together to resist the vibration and rotationalchain motions at high temperatures. Cross linking is usually extensive in that 10 to 15% of thechain mer units are cross linked. Only heating to excessive temperatures will cause severance ofthese crosslink bonds and polymer degradation.

Thermoset polymers are harder, stronger, more brittle than thermoplastics and have betterdimensional stability.

They are more usable in processes requiring high temperatures Most of the cross linked and network polymers which include

o Vulcanized rubberso Epoxieso Phenolico Polyester resins

are thermosetting.

Thermosets cannot be recycle, do not melt, are usable at higher temperatures than thermoplastics,and are more chemically inert

THERMOPLASTIC

A thermoplastic , also known as a thermosoftening plastic , is a polymer that turns to a liquidwhen heated and freezes to a very glassy state when cooled sufficiently. Most thermoplastics are high-molecular-weight polymers whose chains associate through weak Van der Waals forces (polyethylene) ;stronger dipole-dipole interactions and hydrogen bonding (nylon) ; or even stacking of aromatic rings(polystyrene) . Thermoplastic polymers differ from thermosetting polymers (Bakelite) in that they can be

remelted and remoulded. Many thermoplastic materials are addition polymers; e.g., vinyl chain-growth polymers such as polyethylene and polypropylene.
http://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Molecular_masshttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Chain_%28sequence%29http://en.wikipedia.org/wiki/Van_der_Waals_forcehttp://en.wikipedia.org/wiki/Polyethylenehttp://en.wikipedia.org/wiki/Dipolehttp://en.wikipedia.org/wiki/Hydrogen_bondhttp://en.wikipedia.org/wiki/Nylonhttp://en.wikipedia.org/wiki/Aromatichttp://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Thermosetting_plastichttp://en.wikipedia.org/wiki/Bakelitehttp://en.wikipedia.org/wiki/Addition_polymerhttp://en.wikipedia.org/wiki/Vinylhttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Vinylhttp://en.wikipedia.org/wiki/Addition_polymerhttp://en.wikipedia.org/wiki/Bakelitehttp://en.wikipedia.org/wiki/Thermosetting_plastichttp://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Aromatichttp://en.wikipedia.org/wiki/Nylonhttp://en.wikipedia.org/wiki/Hydrogen_bondhttp://en.wikipedia.org/wiki/Dipolehttp://en.wikipedia.org/wiki/Polyethylenehttp://en.wikipedia.org/wiki/Van_der_Waals_forcehttp://en.wikipedia.org/wiki/Chain_%28sequence%29http://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Molecular_masshttp://en.wikipedia.org/wiki/Polymer


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Theory

Stress strain graph of thermoplastic material.

Thermoplastics are elastic and flexible above a glass transition temperature T g, specific for eachone the midpoint of a temperature range in contrast to the sharp melting point of a pure crystallinesubstance like water. Below a second, higher melting temperature, T m, also the midpoint of a range, mostthermoplastics have crystalline regions alternating with amorphous regions in which the chainsapproximate random coils. The amorphous regions contribute elasticity and the crystalline regionscontribute strength and rigidity, as is also the case for non-thermoplastic fibrous proteins such as silk.

(Elasticity does not mean they are particularly stretchy; e.g., nylon rope and fishing line. ) Above T m allcrystalline structure disappears and the chains become randomly inter dispersed. As the temperatureincreases above T m, viscosity gradually decreases without any distinct phase change.

Some thermoplastics normally do not crystallize: they are termed amorphous plastics and areuseful at temperatures below the T g. They are frequently used in applications where clarity is important.Some typical examples of amorphous thermoplastics are PMMA, PS and PC. Generally, amorphousthermoplastics are less chemically resistant and can be subject to environmental stress cracking. Thermoplastics will crystallize to a certain extent and are called semi-crystalline for this reason.Typical semi-crystalline thermoplastics are PE, PP, PBT and PET. The speed and extent to whichcrystallization can occur depends in part on the flexibility of the polymer chain. Semi-crystallinethermoplastics are more resistant to solvents and other chemicals. If the crystallites are larger than the

wavelength of light, the thermoplastic is hazy or opaque.

Semi-crystalline thermoplastics become less brittle above T g. If a plastic with otherwise desirable properties has too high a T g, it can often be lowered by adding a low-molecular-weight plasticizer to themelt before forming (Plastics extrusion; molding) and cooling. A similar result can sometimes beachieved by adding non-reactive side chains to the monomers before polymerization. Both methods makethe polymer chains stand off a bit from one another. Before the introduction of plasticizers, plasticautomobile parts often cracked in cold winter weather. Another method of lowering T g (or raising T m) isto incorporate the original plastic into a copolymer, as with graft copolymers of polystyrene, or into acomposite material. Lowering T g is not the only way to reduce brittleness. Drawing (and similar processesthat stretch or orient the molecules) or increasing the length of the polymer chains also decrease

brittleness.

Thermoplastics can go through melting/freezing cycles repeatedly and the fact that they can bereshaped upon reheating gives them their name. This quality makes thermoplastics recyclable. The

processes required for recycling vary with the thermoplastic. The plastics used for soda bottles are acommon example of thermoplastics that can be and are widely recycled. Animal horn, made of the protein-keratin, softens on heating, is somewhat reshapable, and may be regarded as a natural, quasi-thermoplastic material.
http://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Amorphous_solidhttp://en.wikipedia.org/wiki/Random_coilhttp://en.wikipedia.org/wiki/Hooke%27s_lawhttp://en.wikipedia.org/wiki/Fibrous_proteinhttp://en.wikipedia.org/wiki/Silkhttp://en.wikipedia.org/wiki/Ropehttp://en.wikipedia.org/wiki/Fishing_linehttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Phase_%28matter%29http://en.wikipedia.org/wiki/Poly%28methyl_methacrylate%29http://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Polycarbonatehttp://en.wikipedia.org/wiki/Environmental_stress_crackinghttp://en.wikipedia.org/wiki/Polyethylenehttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Polybutylene_terephthalatehttp://en.wikipedia.org/wiki/Polyethylene_terephthalatehttp://en.wikipedia.org/wiki/Plasticizerhttp://en.wikipedia.org/wiki/Plastics_extrusionhttp://en.wikipedia.org/wiki/Molding_%28process%29http://en.wikipedia.org/wiki/Side_chainhttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Polymerizationhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Weatherhttp://en.wikipedia.org/wiki/Copolymerhttp://en.wikipedia.org/wiki/Graft_copolymerhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Drawing_%28manufacturing%29http://en.wikipedia.org/wiki/Horn_%28anatomy%29http://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Keratinhttp://en.wikipedia.org/wiki/Keratinhttp://en.wikipedia.org/wiki/Keratinhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Horn_%28anatomy%29http://en.wikipedia.org/wiki/Drawing_%28manufacturing%29http://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Graft_copolymerhttp://en.wikipedia.org/wiki/Copolymerhttp://en.wikipedia.org/wiki/Weatherhttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Polymerizationhttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Side_chainhttp://en.wikipedia.org/wiki/Molding_%28process%29http://en.wikipedia.org/wiki/Plastics_extrusionhttp://en.wikipedia.org/wiki/Plasticizerhttp://en.wikipedia.org/wiki/Polyethylene_terephthalatehttp://en.wikipedia.org/wiki/Polybutylene_terephthalatehttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Polyethylenehttp://en.wikipedia.org/wiki/Environmental_stress_crackinghttp://en.wikipedia.org/wiki/Polycarbonatehttp://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Poly%28methyl_methacrylate%29http://en.wikipedia.org/wiki/Phase_%28matter%29http://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Fishing_linehttp://en.wikipedia.org/wiki/Ropehttp://en.wikipedia.org/wiki/Silkhttp://en.wikipedia.org/wiki/Fibrous_proteinhttp://en.wikipedia.org/wiki/Hooke%27s_lawhttp://en.wikipedia.org/wiki/Random_coilhttp://en.wikipedia.org/wiki/Amorphous_solidhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperature


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Although modestly vulcanized natural and synthetic rubbers are stretchy, they are elastomericthermosets, not thermoplastics. Each has its own T g, and will crack and shatter when cold enough so thatthe crosslinked polymer chains can no longer move relative to one another. But they have no T m and willdecompose at high temperatures rather than melt. Recently, thermoplastic elastomers have becomeavailable.

TERMINOLOGY

The literature on thermoplastics is huge, and can be quite confusing, as the same chemical can beavailable in many different forms (for example, at different molecular weights), which might have quitedifferent physical properties. The same chemical can be referred to by many different tradenames, bydifferent abbreviations; two chemical compounds can share the same name; a good example of the latteris the word Teflon which is used to refer to a specific polymer (PTFE); to related polymers such asPFA, and generically to fluoropolymers.

TESTING

Testing of thermoplastics can take various forms.

Tensile tests ISO 527 -1/-2 and ASTM D 638 set out the standardized test methods. These standards aretechnically equivalent. However they are not fully comparable because of the difference in testing speeds.The modulus determination requires a high accuracy of 1 micrometer for the dilatometer.

Flexural tests 3-points flexural tests are among the most common and classic methods for semi rigidand rigid plastics.

Pendulum impact tests impact tests are used to measure the behavior of materials at higherdeformation speeds. Pendulum impact testers are used to determine the energy required to break astandardized specimen by measuring the height to which the pendulum hammer rises after impacting the

test piece.

PROPERTIES OF THERMOPLASTICS:

Typical values of some common thermoplastics can be found in the table below.

ThermoplasticSpecificGravity

TensileYieldStrength(10 3 psi )

TensileModulus(10 3 psi )

Coefficientsof LinearExpansion(10 6 in/in o F )

ThermalConductivity(Btu in /h ft 2 o F )

SpecificHeat(Btu/lbo F )

MaximumTemperatureLimit(o F / o C )

ABS 1.08 7.0 340 60 1.35 0.34 180/80

PVC 1.4 8.0 410 30 1.1 0.25 150/65
http://en.wikipedia.org/wiki/Elastomerhttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Thermoplastic_elastomerhttp://en.wikipedia.org/wiki/Fluoropolymerhttp://en.wikipedia.org/wiki/Dilatometerhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://www.engineeringtoolbox.com/young-modulus-d_417.htmlhttp://www.engineeringtoolbox.com/young-modulus-d_417.htmlhttp://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.htmlhttp://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.htmlhttp://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.htmlhttp://www.engineeringtoolbox.com/conductive-heat-transfer-d_428.htmlhttp://www.engineeringtoolbox.com/conductive-heat-transfer-d_428.htmlhttp://www.engineeringtoolbox.com/specific-heat-capacity-d_339.htmlhttp://www.engineeringtoolbox.com/specific-heat-capacity-d_339.htmlhttp://www.engineeringtoolbox.com/specific-heat-capacity-d_339.htmlhttp://www.engineeringtoolbox.com/specific-heat-capacity-d_339.htmlhttp://www.engineeringtoolbox.com/conductive-heat-transfer-d_428.htmlhttp://www.engineeringtoolbox.com/conductive-heat-transfer-d_428.htmlhttp://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.htmlhttp://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.htmlhttp://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.htmlhttp://www.engineeringtoolbox.com/young-modulus-d_417.htmlhttp://www.engineeringtoolbox.com/young-modulus-d_417.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://en.wikipedia.org/wiki/Dilatometerhttp://en.wikipedia.org/wiki/Fluoropolymerhttp://en.wikipedia.org/wiki/Thermoplastic_elastomerhttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Elastomer


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CPVC 1.54 8.0 420 35 1.0 0.20 210/100

PE 0.95 3.2 120 90 3.2 0.55 160/70

PEX 0.94 2.8 . 90 3.2 0.55 210/100

PB 0.92 4.2 55 72 1.5 0.45 210/100

PVDF 1.76 7.0 220 70 1.5 0.29 300/150

1 psi (lb/in 2 ) = 6,894.8 Pa (N/m 2 ) Note! You can use the pressure unit converter on this page to switch to Pa (N/m 2 ) units.

1 (Btu/lb o F) = 4,186.8 (J/kg K) = 1 (kcal/kg oC)

TENSILE YIELD STRENGTH

Tensile yield strength is the maximum engineering stress in psi (or Pa) at which a permanent non-elastic deformation of the thermoplastic material begins.

YIELD POINT

Yield point is the first point where the specimen yields, where the specimen s cross-sectional area begins to contract significantly, or where the strain can increase without increase in the stress.

ULTIMATE TENSILE STRENGTH

Ultimate tensile strength is the maximum stress the thermoplastic material can withstand beforefailing, whichever occurs at the higher stress level.

TENSILE MODULUS

Tensile modulus or Young s Modulus is the ratio of stress to strain within the elastic region of thestress-strain curve before the yield point.

THERMOPLASTIC CHARACTERISTICS

ABS Acrylonitrile Butadiene Styrene

strong and rigid resistant to a variety of bases and acids some solvents and chlorinated hydrocarbons may damage the material maximum usable temperature 160 o F (71 oC) common as DEV Drainage, Waste and Vent pipes
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PB Polybutylene

flexible pipe used for pressurized water systems usable for hot and cold water only compression and banded type joints used

PE Polyethylene

flexible pipe used for pressurized water systems sprinkler.. not usable for hot water

PEX Polyethylene Cross Linked

flexible pipe used for pressurized water systems sprinkler..

PP Polypropylene

lightweight temperature up to 180 o F (82 oC) highly resistant to acids, bases and many solvents usable in laboratory plumbing

PVC Polyvinyl Chloride

strong and rigid

resistant to a variety of acids and bases may be damaged by some solvents and chlorinated hydrocarbons maximum usable temperature 140 o F (60 oC) usable for water, gas and drainage systems not useable in hot water systems

CPVC Chlorinated Polyvinyl Chloride

similar to PVC but designed for water up to 180 o F (82 oC)

PVDF Polyvinylidene Fluoride

strong and very tough material resistant to abrasion, acids, bases, solvents and much more usable to 280 o F (138 oC) usable in laboratory plumbing


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THERMOSETTING PLASTICS

A thermosetting plastic , also known as a thermoset , is polymer material that irreversibly cures. The cure may be done through heat (generally above 200 C (392 F)), through a chemical reaction (two-

part epoxy, for example), or irradiation such as electron beam processing.

Thermoset materials are usually liquid or malleable prior to curing and designed to be moldedinto their final form, or used as adhesives. Others are solids like that of the molding compound used insemiconductors and integrated circuits (IC).

According to IUPAC recommendation: A thermosetting polymer is a prepolymer in a soft solid orviscous state that changes irreversibly into an infusible, insoluble polymer network by curing. Curing can

be induced by the action of heat or suitable radiation, or both. A cured thermosetting polymer is called athermoset.

PROCESS

The curing process transforms the resin into a plastic or rubber by a cross-linking process. Energyand/or catalysts are added that cause the molecular chains to react at chemically active sites (unsaturatedor epoxy sites, for example), linking into a rigid, 3-D structure. The cross-linking process forms amolecule with a larger molecular weight, resulting in a material with a higher melting point. During thereaction, the molecular weight has increased to a point so that the melting point is higher than thesurrounding ambient temperature, the material forms into a solid material.

Uncontrolled reheating of the material results in reaching the decomposition temperature beforethe melting point is obtained. Therefore, a thermoset material cannot be melted and re-shaped after it iscured. This implies that thermosets cannot be recycled, except as filler material.

STATISTICS

Thermoset materials are generally stronger than thermoplastic materials due to this 3-D networkof bonds (cross-linking), and are also better suited to high -temperature applications up to thedecomposition temperature. However, they are more brittle.

ECOLOGY

Many thermosetting polymers are difficult to recycle.

EXAMPLES

Some examples of thermosets are:

Polyester fiberglass systems: (SMC Sheet molding compounds and BMC Bulk moldingcompounds)

Vulcanized rubber Bakelite, a phenol-formaldehyde resin (used in electrical insulators and plasticware) Duroplast, light but strong material, similar to Bakelite (used for making car parts) Urea-formaldehyde foam (used in plywood, particleboard and medium-density fibreboard)
http://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Curing_%28chemistry%29http://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Irradiationhttp://en.wikipedia.org/wiki/Electron_beam_processinghttp://en.wikipedia.org/wiki/Malleablehttp://en.wikipedia.org/wiki/Molding_%28process%29http://en.wikipedia.org/wiki/Adhesivehttp://en.wikipedia.org/wiki/Semiconductorshttp://en.wikipedia.org/wiki/Integrated_circuitshttp://en.wikipedia.org/wiki/IUPAChttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Catalysthttp://en.wikipedia.org/wiki/Dimensionhttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Melthttp://en.wikipedia.org/wiki/Melthttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Vulcanizationhttp://en.wikipedia.org/wiki/Bakelitehttp://en.wikipedia.org/wiki/Duroplasthttp://en.wikipedia.org/wiki/Urea-formaldehydehttp://en.wikipedia.org/wiki/Plywoodhttp://en.wikipedia.org/wiki/Plywoodhttp://en.wikipedia.org/wiki/Urea-formaldehydehttp://en.wikipedia.org/wiki/Duroplasthttp://en.wikipedia.org/wiki/Bakelitehttp://en.wikipedia.org/wiki/Vulcanizationhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wikipedia.org/wiki/Melthttp://en.wikipedia.org/wiki/Melthttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Dimensionhttp://en.wikipedia.org/wiki/Catalysthttp://en.wikipedia.org/wiki/Cross-linkhttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/IUPAChttp://en.wikipedia.org/wiki/Integrated_circuitshttp://en.wikipedia.org/wiki/Semiconductorshttp://en.wikipedia.org/wiki/Adhesivehttp://en.wikipedia.org/wiki/Molding_%28process%29http://en.wikipedia.org/wiki/Malleablehttp://en.wikipedia.org/wiki/Electron_beam_processinghttp://en.wikipedia.org/wiki/Irradiationhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Curing_%28chemistry%29http://en.wikipedia.org/wiki/Polymer


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Melamine resin (used on worktop surfaces) Epoxy resin (used as the matrix component in many fibre reinforced plastics such as glass

reinforced plastic and graphite-reinforced plastic) Polyimides (used in printed circuit boards and in body parts of modern airplanes) Cyanate Esters or Polycyanurates for electronics applications with high demands on dielectric

properties and high glass temperature requirements in composites Mold or Mold Runners (the black plastic part in Integrated Circuits (IC) or semiconductors)

Some methods of molding thermosets are:

Reactive injection molding (used for objects such as milk bottle crates) Extrusion molding (used for making pipes, threads of fabric and insulation for electrical cables) Compression molding (used to shape most thermosetting plastics) Spin casting (used for producing fishing lures and jigs, gaming miniatures, figurines, emblems as

well as production and replacement parts)

WHAT IS THE DIFFERENCE BETWEEN THERMOSETTING AND THERMOPLASTICS?

The difference between thermoplastics and thermosetting plastics is that thermoplastics becomesoft, remoldable and weldable when heat is added. Thermosetting plastics however, when heated, willchemically decompose, so they can not be welded or remolded. On the other hand, once a thermosetting iscured it tends to be stronger than a thermoplastic.

BENEFITS IN THERMOSETTING PLASTICS AND REACTIVE RESINS

The unique structure of Neuburg Siliceous Earth gives rise, in addition to the product characteristicsmentioned, to further benefits with respect to:

Special rheological properties: depending on requirements, self-running as well as dimensionallystable coatings can be formulated

Good physical properties: tear resistance, tensile strength, moduli Good scratch and abrasion resistance Good weather resistance Good chemical resistance Excellent surface finish
http://en.wikipedia.org/wiki/Melamine_resinhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Fibre_reinforced_plastichttp://en.wikipedia.org/wiki/Graphite-reinforced_plastichttp://en.wikipedia.org/wiki/Polyimideshttp://en.wikipedia.org/wiki/Injection_moldinghttp://en.wikipedia.org/wiki/Extrusion_moldinghttp://en.wikipedia.org/wiki/Compression_moldinghttp://en.wikipedia.org/wiki/Spin_castinghttp://en.wikipedia.org/wiki/Fishing_lurehttp://en.wikipedia.org/wiki/Jig_%28fishing%29http://en.wikipedia.org/wiki/Miniature_figure_%28gaming%29http://en.wikipedia.org/wiki/Figurinehttp://en.wikipedia.org/wiki/Figurinehttp://en.wikipedia.org/wiki/Miniature_figure_%28gaming%29http://en.wikipedia.org/wiki/Jig_%28fishing%29http://en.wikipedia.org/wiki/Fishing_lurehttp://en.wikipedia.org/wiki/Spin_castinghttp://en.wikipedia.org/wiki/Compression_moldinghttp://en.wikipedia.org/wiki/Extrusion_moldinghttp://en.wikipedia.org/wiki/Injection_moldinghttp://en.wikipedia.org/wiki/Polyimideshttp://en.wikipedia.org/wiki/Graphite-reinforced_plastichttp://en.wikipedia.org/wiki/Fibre_reinforced_plastichttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Melamine_resin


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UNIT 2 PROCESSING OF POLYMERS

EXTRUSION

Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is

pushed or drawn through a die of the desired cross-section. The two main advantages of this process overother manufacturing processes are its ability to create very complex cross-sections and work materialsthat are brittle, because the material only encounters compressive and shear stresses. It also forms finished

parts with an excellent surface finish.

Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). The extrusion process can be done with the material hot or cold.

Commonly extruded materials include metals, polymers, ceramics, concrete and foodstuffs.

Hollow cavities within extruded material cannot be produced using a simple flat extrusion die, because there would be no way to support the center barrier of the die. Instead, the die assumes the shapeof a block with depth, beginning first with a shape profile that supports the center section. The die shapethen internally changes along its length into the final shape, with the suspended center pieces supportedfrom the back of the die.

Pr ocess

Extrusion of a round blank through a die.

The process begins by heating the stock material (for hot or warm extrusion). It is then loadedinto the container in the press. A dummy block is placed behind it where the ram then presses on thematerial to push it out of the die. Afterward the extrusion is stretched in order to straighten it. If better

properties are required then it may be heat treated or cold worked.

The extrusion ratio is defined as the starting cross-sectional area divided by the cross-sectionalarea of the final extrusion. One of the main advantages of the extrusion process is that this ratio can bevery large while still producing quality parts.
http://en.wikipedia.org/wiki/Cross_section_%28geometry%29http://en.wikipedia.org/wiki/Die_%28manufacturing%29http://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Ceramichttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Heat_treathttp://en.wikipedia.org/wiki/Cold_workhttp://en.wikipedia.org/wiki/Cold_workhttp://en.wikipedia.org/wiki/Heat_treathttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Ceramichttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Shear_stresshttp://en.wikipedia.org/wiki/Compressive_stresshttp://en.wikipedia.org/wiki/Die_%28manufacturing%29http://en.wikipedia.org/wiki/Cross_section_%28geometry%29


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HOT EXTRUSION

Hot extrusion is a hot working process, which means it is done above the material'srecrystallization temperature to keep the material from work hardening and to make it easier to push thematerial through the die. Most hot extrusions are done on horizontal hydraulic presses that range from230 to 11,000 metric tons (250 to 12,000 short tons). Pressures range from 30 to 700 MPa (4,400 to100,000 psi), therefore lubrication is required, which can be oil or graphite for lower temperatureextrusions, or glass powder for higher temperature extrusions. The biggest disadvantage of this process isits cost for machinery and its upkeep.

Hot extrusion temperature for various metal s[1]

Material Temperature [C (F)]

Magnesium 350-450 (650-850)

Aluminium 350-500 (650-900)

Copper 600-1100 (1200-2000)

Steel 1200-1300 (2200 2400)

Titanium 700-1200 (1300-2100)

Nickel 1000-1200 (1900 2200)

Refractory alloys up to 2000 (4000)
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The extrusion process is generally economical when producing between several kilograms(pounds) and many tons, depending on the material being extruded. There is a crossover point where rollforming becomes more economical. For instance, some steels become more economical to roll if

producing more than 20,000 kg (50,000 lb).

COLD EXTRUSION

Cold extrusion is done at room temperature or near room temperature. The advantages of thisover hot extrusion are the lack of oxidation, higher strength due to cold working, closer tolerances, goodsurface finish, and fast extrusion speeds if the material is subject to hot shortness.

Materials that are commonly cold extruded include: lead, tin, aluminum, copper, zirconium,titanium, molybdenum, beryllium, vanadium, niobium, and steel.

Examples of products produced by this process are: collapsible tubes, fire extinguisher cases,shock absorber cylinders, automotive pistons, and gear blanks.

WARM EXTRUSION

Warm extrusion is done above room temperature, but below the recrystallization temperature ofthe material the temperatures ranges from 800 to 1800 F (424 to 975 C). It is usually used to achieve the

proper balance of required forces, ductility and final extrusion properties.

EQUIPMENT

A horizontal hydraulic press for hot aluminum extrusion (loose dies and scrap visible inforeground)

There are many different variations of extrusion equipment. They vary by four major characteristics:

1. Movement of the extrusion with relation to the ram. If the die is held stationary and the rammoves towards it then its called "direct extrusion". If the ram is held stationary and the die movestowards the ram its called "indirect extrusion".

2. The position of the press, either vertical or horizontal.3. The type of drive, either hydraulic or mechanical.4. The type of load applied, either conventional (variable) or hydrostatic.

A single or twin screw auger, powered by an electric motor, or a ram, driven by hydraulic pressure(often used for steel and titanium alloys), oil pressure (for aluminum), or in other specialized processessuch as rollers inside a perforated drum for the production of many simultaneous streams of material.

Typical extrusion presses cost more than $100,000, whereas dies can cost up to $2000.
http://en.wikipedia.org/wiki/Roll_forminghttp://en.wikipedia.org/wiki/Roll_forminghttp://en.wikipedia.org/wiki/Cold_workinghttp://en.wikipedia.org/w/index.php?title=Hot_shortness&action=edit&redlink=1http://en.wikipedia.org/wiki/Fire_extinguisherhttp://en.wikipedia.org/wiki/Shock_absorberhttp://en.wikipedia.org/wiki/Hydrostatichttp://en.wikipedia.org/wiki/Hydrostatichttp://en.wikipedia.org/wiki/Shock_absorberhttp://en.wikipedia.org/wiki/Fire_extinguisherhttp://en.wikipedia.org/w/index.php?title=Hot_shortness&action=edit&redlink=1http://en.wikipedia.org/wiki/Cold_workinghttp://en.wikipedia.org/wiki/Roll_forminghttp://en.wikipedia.org/wiki/Roll_forming


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entire length of the container. Because of this the greatest force required is at the beginning of process andslowly decreases as the billet is used up. At the end of the billet the force greatly increases because the

billet is thin and the material must flow radially to exit the die. The end of the billet (called the butt end)is not used for this reason.

INDIRECT EXTRUSION

In indirect extrusion, also known as backwards extrusion, the billet and container move togetherwhile the die is stationary. The die is held in place by a "stem" which has to be longer than the containerlength. The maximum length of the extrusion is ultimately dictated by the column strength of the stem.Because the billet moves with the container the frictional forces are eliminated. This leads to thefollowing advantages:

A 25 to 30% reduction of friction, which allows for extruding larger billets, increasing speed, andan increased ability to extrude smaller cross-sections

There is less of a tendency for extrusions to crack because there is no heat formed from friction The container liner will last longer due to less wear The billet is used more uniformly so extrusion defects and coarse grained peripherals zones are

less likely.

The disadvantages are:

Impurities and defects on the surface of the billet affect the surface of the extrusion. These defectsruin the piece if it needs to be anodized or the aesthetics are important. In order to get around thisthe billets may be wire brushed, machined or chemically cleaned before being used.

This process isn't as versatile as direct extrusions because the cross-sectional area is limited bythe maximum size of the stem.

HYDROSTATIC EXTRUSION

In the hydrostatic extrusion process the billet is completely surrounded by a pressurized liquid, exceptwhere the billet contacts the die. This process can be done hot, warm, or cold, however the temperature islimited by the stability of the fluid used. The process must be carried out in a sealed cylinder to containthe hydrostatic medium. The fluid can be pressurized two ways:

1. Constant-rate extrusion : A ram or plunger is used to pressurize the fluid inside the container.2. Constant-pressure extrusion : A pump is used, possibly with a pressure intensifier, to pressurize

the fluid, which is then pumped to the container.

The advantages of this process include:

No friction between the container and the billet reduces force requirements. This ultimatelyallows for faster speeds, higher reduction ratios, and lower billet temperatures.

Usually the ductility of the material increases when high pressures are applied. An even flow of material. Large billets and large cross-sections can be extruded. No billet residue is left on the container walls.
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The disadvantages are:

The billets must be prepared by tapering one end to match the die entry angle. This is needed toform a seal at the beginning of the cycle. Usually the entire billet needs to be machined to removeany surface defects.

Containing the fluid under high pressures can be difficult.

DRIVES

Most modern direct or indirect extrusion presses are hydraulically driven, but there are somesmall mechanical presses still used. Of the hydraulic presses there are two types: direct-drive oil pressesand accumulator water drives.

Direct-drive oil presses are the most common because they are reliable and robust. They candeliver over 35 MPa (5000 psi). They supply a constant pressure throughout the whole billet. Thedisadvantage is that they are slow, between 50 and 200 mm/s (2 8 ips).

Accumulator water drives are more expensive and larger than direct-drive oil presses, and theylose about 10% of their pressure over the stroke, but they are much faster, up to 380 mm/s (15ips). Because of this they are used when extruding steel. They are also used on materials thatmust be heated to very hot temperatures for safety reasons.

Hydrostatic extrusion presses usually use castor oil at pressure up to 1400 MPa (200 ksi). Castoroil is used because it has good lubricity and high pressure properties.

EXTRUSION DEFECTS

Surface cracking - When the surface of an extrusion splits. This is often caused by the extrusiontemperature, friction, or speed being too high. It can also happen at lower temperatures if theextruded product temporarily sticks to the die.

Pipe - A flow pattern that draws the surface oxides and impurities to the center of the product.Such a pattern is often caused by high friction or cooling of the outer regions of the billet.

Internal cracking - When the center of the extrusion develops cracks or voids. These cracks areattributed to a state of hydrostatic tensile stress at the centerline in the deformation zone in thedie. (A similar situation to the necked region in a tensile stress specimen)

Surface lines - When there are lines visible on the surface of the extruded profile. This dependsheavily on the quality of the die production and how well the die is maintained, as some residuesof the material extruded can stick to the die surface and produce the embossed lines.

MATERIALS

METAL

Metals that are commonly extruded include:

Aluminium is the most commonly extruded material. Aluminium can be hot or cold extruded. Ifit is hot extruded it is heated to 575 to 1100 F (300 to 600 C). Examples of products include

profiles for tracks, frames, rails, mullions, and heat sinks.
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Copper (1100 to 1825 F (600 to 1000 C)) pipe, wire, rods, bars, tubes, and welding electrodes.Often more than 100 ksi (690 MPa) is required to extrude copper.

Lead and tin (maximum 575 F (300 C)) pipes, wire, tubes, and cable sheathing. Molten leadmay also be used in place of billets on vertical extrusion presses.

Magnesium (575 to 1100 F (300 to 600 C)) aircraft parts and nuclear industry parts.Magnesium is about as extrudable as aluminum.

Zinc (400 to 650 F (200 to 350 C)) rods, bar, tubes, hardware components, fitting, andhandrails.

Steel (1825 to 2375 F (1000 to 1300 C)) rods and tracks. Usually plain carbon steel is extruded, but alloy steel and stainless steel can also be extruded.

Titanium (1100 to 1825 F (600 to 1000 C)) aircraft components including seat tracks, enginerings, and other structural parts.

Magnesium and aluminium alloys usually have a 0.75 m (30 in) RMS or better surface finish.Titanium and steel can achieve a 3 micrometres (120 in) RMS.

In 1950, Ugine Sjournet, of France, invented a process which uses glass as a lubricant for extrudingsteel. The Ugine-Sejournet, or Sejournet, process is now used for other materials that have meltingtemperatures higher than steel or that require a narrow range of temperatures to extrude. The processstarts by heating the materials to the extruding temperature and then rolling it in glass powder. The glassmelts and forms a thin film, 20 to 30 mils (0.5 to 0.75 mm), in order to separate it from chamber wallsand allow it to act as a lubricant. A thick solid glass ring that is 0.25 to 0.75 in (6 to 18 mm) thick is

placed in the chamber on the die to lubricate the extrusion as it is forced through the die. A secondadvantage of this glass ring is its ability to insulate the heat of the billet from the die. The extrusion willhave a 1 mil thick layer of glass, which can be easily removed once it cools.

Another breakthrough in lubrication is the use of phosphate coatings. With this process, inconjunction with glass lubrication, steel can be cold extruded. The phosphate coat absorbs the liquid glassto offer even better lubricating properties.

PLASTIC

Plastics extrusion commonly uses plastic chips or pellets, which are usually dried in a hopper before going to the feed screw. The polymer resin is heated to molten state by a combination of heatingelements and shear heating from the extrusion screw. The screw forces the resin through a die, formingthe resin into the desired shape. The extrudate is cooled and solidified as it is pulled through the die orwater tank. In some cases (such as fibre-reinforced tubes) the extrudate is pulled through a very long die,in a process called pultrusion.
http://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Plain_carbon_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/Thou_%28length%29http://en.wikipedia.org/wiki/Plastics_extrusionhttp://en.wikipedia.org/wiki/Plastics_extrusionhttp://en.wikipedia.org/wiki/Thou_%28length%29http://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/Root_mean_squarehttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Plain_carbon_steelhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Copper


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A multitude of polymers are used in the production of plastic tubing, pipes, rods, rails, seals, andsheets or films.

CERAMIC

Ceramic can also be formed into shapes via extrusion. Terracotta extrusion is used to produce pipes. Many modern bricks are also manufactured using a brick extrusion process.

FOOD

Extrusion has application in food processing. Products such as certain pastas, many breakfastcereals, Fig Newtons, premade cookie dough, Murukku, Sevai, Idiappam, jalebi, some french fries, certain baby foods, dry pet food and ready-to-eat snacks are mostly manufactured by extrusion. In theextrusion process, raw materials are first ground to the correct particle size (usually the consistency ofcoarse flour). The dry mix is passed through a pre-conditioner, where other ingredients are added (liquid

sugar, fats, dyes, meats and water depending on the product being made), steam is injected to start thecooking process. The preconditioned mix is then passed through an extruder, and then forced through adie where it is cut to the desired length. The cooking process takes place within the extruder where the

product produces its own friction and heat due to the pressure generated (10 20 bar). The process caninduce both protein denaturation and starch gelatinization, depending on inputs and parameters. Extrudersusing this process have a capacity from 1 25 tonnes per hour depending on design.

As with other forms of cooking, extrusion achieves the following nutritionally:

Inactivation of raw food enzymes Destruction of certain naturally occurring toxins Diminishing of microorganisms in the final product

Slight increase of iron-bioavailability Creation of insulin-desensitizing starches, which are a risk-factor for developing diabetes Loss of the essential amino: lysine, which is essential to developmental growth and nitrogen

management Simplification of complex starches, increasing rates of tooth decay Marked increase of processed foods' glycemic indexes Destruction of Vitamin A (beta-carotene)
http://en.wikipedia.org/wiki/Terracottahttp://en.wikipedia.org/wiki/Pastahttp://en.wikipedia.org/wiki/Breakfast_cerealhttp://en.wikipedia.org/wiki/Breakfast_cerealhttp://en.wikipedia.org/wiki/Fig_Newtonshttp://en.wikipedia.org/wiki/Cookie_doughhttp://en.wikipedia.org/wiki/Murukkuhttp://en.wikipedia.org/wiki/Sevaihttp://en.wikipedia.org/wiki/Idiappamhttp://en.wikipedia.org/wiki/Jalebihttp://en.wikipedia.org/wiki/French_frieshttp://en.wikipedia.org/w/index.php?title=Baby_foods&action=edit&redlink=1http://en.wikipedia.org/wiki/Pet_foodhttp://en.wikipedia.org/wiki/Sugarhttp://en.wikipedia.org/wiki/Fatshttp://en.wikipedia.org/wiki/Dyeshttp://en.wikipedia.org/wiki/Meatshttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Protein_denaturationhttp://en.wikipedia.org/wiki/Starch_gelatinizationhttp://en.wikipedia.org/wiki/Enzymeshttp://en.wikipedia.org/wiki/Toxinshttp://en.wikipedia.org/wiki/Microorganismhttp://en.wikipedia.org/wiki/Type_II_Diabeteshttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Lysinehttp://en.wikipedia.org/wiki/Glycemic_indexhttp://en.wikipedia.org/wiki/Beta-carotenehttp://en.wikipedia.org/wiki/Beta-carotenehttp://en.wikipedia.org/wiki/Glycemic_indexhttp://en.wikipedia.org/wiki/Lysinehttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Type_II_Diabeteshttp://en.wikipedia.org/wiki/Microorganismhttp://en.wikipedia.org/wiki/Toxinshttp://en.wikipedia.org/wiki/Enzymeshttp://en.wikipedia.org/wiki/Starch_gelatinizationhttp://en.wikipedia.org/wiki/Protein_denaturationhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Meatshttp://en.wikipedia.org/wiki/Dyeshttp://en.wikipedia.org/wiki/Fatshttp://en.wikipedia.org/wiki/Sugarhttp://en.wikipedia.org/wiki/Pet_foodhttp://en.wikipedia.org/w/index.php?title=Baby_foods&action=edit&redlink=1http://en.wikipedia.org/wiki/French_frieshttp://en.wikipedia.org/wiki/Jalebihttp://en.wikipedia.org/wiki/Idiappamhttp://en.wikipedia.org/wiki/Sevaihttp://en.wikipedia.org/wiki/Murukkuhttp://en.wikipedia.org/wiki/Cookie_doughhttp://en.wikipedia.org/wiki/Fig_Newtonshttp://en.wikipedia.org/wiki/Breakfast_cerealhttp://en.wikipedia.org/wiki/Breakfast_cerealhttp://en.wikipedia.org/wiki/Pastahttp://en.wikipedia.org/wiki/Terracotta


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Extrusion is also used to modify starch and to pellet animal feed.

DRUG CARRIERS

Extrusion through nano-porous, polymeric filters is being used to manufacture suspensions oflipid vesicles liposomes or Transfersomes for use in pharmaceutical products. The anti-cancer drugDoxorubicin in liposome delivery system is formulated by extrusion, for example.

BIOMASS BRIQUETTES

The extrusion production technology of fuel briquettes is the process of extrusion screw wastes(straw, sunflower husks, buckwheat, etc.) or finely shredded wood waste (sawdust) under high pressurewhen heated from 160 to 350 C. The resulting fuel briquettes do not include any of the binders, but onenatural - the lignin contained in the cells of plant wastes. The temperature during compression, causesmelting of the surface of bricks, making it more solid, which is important for the transportation of

briquettes.

DESIGN

The design of an extrusion profile has a large impact on how readily it can be extruded. Themaximum size for an extrusion is determined by finding the smallest circle that will fit around the cross-section, this is called the circumscribing circle . This diameter, in turn, controls the size of the dierequired, which ultimately determines if the part will fit in a given press. For example, a larger press canhandle 60 cm (24 in) diameter circumscribing circles for aluminium and 55 cm (22 in). Diameter circlesfor steel and titanium.

The complexity of an extruded profile can be roughly quantified by calculating the shape factor ,which is the amount of surface area generated per unit mass of extrusion. This affects the cost of toolingas well as the rate of production.

Thicker sections generally need an increased section size. In order for the material to flow properly legs should not be more than ten times longer than their thickness. If the cross-section isasymmetrical, adjacent sections should be as close to the same size as possible. Sharp corners should beavoided; for aluminium and magnesium the minimum radius should be 0.4 mm (1/64 in) and for steelcorners should be 0.75 mm (0.030 in) and fillets should be 3 mm (0.12 in). The following table lists theminimum cross-section and thickness for various materials.

Material Minimum cross-section [cm (sq. in.)] Minimum thickness [mm (in.)]

Carbon steels 2.5 (0.40) 3.00 (0.120)

Stainless steel 3.0-4.5 (0.45-0.70) 3.00-4.75 (0.120-0.187)

Titanium 3.0 (0.50) 3.80 (0.150)

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EQUIPMENT

An injection molding machine

Injection molding machines consist of a material hopper, an injection ram or screw-type plunger,and a heating unit. They are also known as presses, they hold the molds in which the components areshaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine canexert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The totalclamp force needed is determined by the projected area of the part being molded. This projected area ismultiplied by a clamp force of from 2 to 8 tons for each square inch of the projected areas. As a rule ofthumb, 4 or 5 tons/in 2 can be used for most products. If the plastic material is very stiff, it will requiremore injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The requiredforce can also be determined by the material used and the size of the part, larger parts require higherclamping force.

MOLD

Mold or die are the common terms used to describe the tooling used to produce plastic parts inmolding.

Since molds have been expensive to manufacture, they were usually only used in mass productionwhere thousands of parts were being produced. Typical molds are constructed from hardened steel, pre-hardened steel, aluminum, and/or beryllium-copper alloy. The choice of material to build a mold from is

primarily one of economics; in general, steel molds cost more to construct, but their longer lifespan willoffset the higher initial cost over a higher number of parts made before wearing out. Pre-hardened steelmolds are less wear-resistant and are used for lower volume requirements or larger components. The

typical steel hardness is 38 45 on the Rockwell-C scale.

Hardened steel molds are heat treated after machining. These are by far the superior in terms of wearresistance and lifespan. Typical hardness ranges between 50 and 60 Rockwell-C (HRC). Aluminummolds can cost substantially less, and, when designed and machined with modern computerizedequipment, can be economical for molding tens or even hundreds of thousands of parts. Beryllium copperis used in areas of the mold that require fast heat removal or areas that see the most shear heat generated.
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The molds can be manufactured either by CNC machining or by using Electrical Discharge Machining processes

Injection molding die with side pulls

"A" side of die for 25% glass-filled acetal with 2 side pulls.

Close up of removable insert in "A" side.

"B" side of die with side pull actuators.

Insert removed from die.
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MOLD DESIGN

Standard two plates tooling core and cavity are inserts in a mold base "family mold" of five different parts

The mold consists of two primary components, the injection mold (A plate) and the ejector mold(B plate). Plastic resin enters the mold through a sprue in the injection mold, the sprue bushing is to seal

tightly against the nozzle of the injection barrel of the molding machine and to allow molten plastic toflow from the barrel into the mold, also known as the cavity . The sprue bushing directs the molten plasticto the cavity images through channels that are machined into the faces of the A and B plates. Thesechannels allow plastic to run along them, so they are referred to as runners. The molten plastic flowsthrough the runner and enters one or more specialized gates and into the cavitygeometry to form thedesired part.

The amount of resin required to fill the sprue, runner and cavities of a mold is a shot. Trapped airin the mold can escape through air vents that are ground into the parting line of the mold. If the trappedair is not allowed to escape, it is compressed by the pressure of the incoming material and is squeezed intothe corners of the cavity, where it prevents filling and causes other defects as well. The air can become socompressed that it ignites and burns the surrounding plastic material. To allow for removal of the molded

part from the mold, the mold features must not overhang one another in the direction that the mold opens,unless parts of the mold are designed to move from between such overhangs when the mold opens(utilizing components called Lifters).

Sides of the part that appear parallel with the direction of draw (The axis of the cored position(hole) or insert is parallel to the up and down movement of the mold as it opens and closes )[16] aretypically angled slightly with (draft) to ease release of the part from the mold. Insufficient draft can causedeformation or damage. The draft required for mold release is primarily dependent on the depth of thecavity: the deeper the cavity, the more draft necessary. Shrinkage must also be taken into account whendetermining the draft required. If the skin is too thin, then the molded part will tend to shrink onto thecores that form them while cooling, and cling to those cores or part may warp, twist, blister or crack whenthe cavity is pulled away. The mold is usually designed so that the molded part reliably remains on the

ejector (B) side of the mold when it opens, and draws the runner and the sprue out of the (A) side alongwith the parts. The part then falls freely when ejected from the (B) side. Tunnel gates, also known assubmarine or mold gate, is located below the parting line or mold surface. The opening is machined intothe surface of the mold on the parting line. The molded part is cut (by the mold) from the runner systemon ejection from the mold. Ejector pins, also known as knockout pin, is a circular pin placed in either halfof the mold (usually the ejector half), which pushes the finished molded product, or runner system out ofa mold.
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The standard method of cooling is passing a coolant (usually water) through a series of holesdrilled through the mold plates and connected by hoses to form a continuous pathway. The coolantabsorbs heat from the mold (which has absorbed heat from the hot plastic) and keeps the mold at a propertemperature to solidify the plastic at the most efficient rate.

To ease maintenance and venting, cavities and cores are divided into pieces, called inserts , andsub-assemblies, also called inserts , blocks , or chase blocks . By substituting interchangeable inserts, onemold may make several variations of the same part.

More complex parts are formed using more complex molds. These may have sections calledslides, that move into a cavity perpendicular to the draw direction, to form overhanging part features.When the mold is opened, the slides are pulled away from the plastic part by using stationary angle pinson the stationary mold half. These pins enter a slot in the slides and cause the slides to move backwardwhen the moving half of the mold opens. The part is then ejected and the mold closes. The closing actionof the mold causes the slides to move forward along the angle pins.

Some molds allow previously molded parts to be reinserted to allow a new plastic layer to formaround the first part. This is often referred to as overmolding. This system can allow for production ofone-piece tires and wheels.

Two-shot or multi-shot molds are designed to "overmold" within a single molding cycle and must be processed on specialized injection molding machines with two or more injection units. This process isactually an injection molding process performed twice. In the first step, the base color material is moldedinto a basic shape. Then the second material is injection-molded into the remaining open spaces. Thatspace is then filled during the second injection step with a material of a different color.

A mold can produce several copies of the same parts in a single "shot". The number of"impressions" in the mold of that part is often incorrectly referred to as cavitation. A tool with oneimpression will often be called a single impression(cavity) mold. A mold with 2 or more cavities of thesame parts will likely be referred to as multiple impression (cavity) mold. Some extremely high

production volume molds (like those for bottle caps) can have over 128 cavities.

In some cases multiple cavity tooling will mold a series of different parts in the same tool. Sometoolmakers call these molds family molds as all the parts are related.

EFFECTS ON THE MATERIAL PROPERTIES

The mechanical properties of a part are usually little affected. Some parts can have internalstresses in them. This is one of the reasons why it is desirable to have uniform wall thickness whenmolding. One of the physical property changes is shrinkage. A permanent chemical property change is thematerial thermoset, which can't be remelted to be injected again.

TOOL MATERIALS

Tool steel or beryllium-copper are often used. Mild steel, aluminum, nickel or epoxy are suitableonly for prototype or very short production runs. Modern hard aluminum (7075 and 2024 alloys) with

proper mold design, can easily make molds capable of 100,000 or more part life.
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I NJECTI ON PROCESS

Small injection molder showing hopper, nozzle and die area

With injection molding, granular plastic is fed by gravity from a hopper into a heated barrel. Asthe granules are slowly moved forward by a screw-type plunger, the plastic is forced into a heatedchamber, where it is melted. As the plunger advances, the melted plastic is forced through a nozzle thatrests against the mold, allowing it to enter the mold cavity through a gate and runner system. The mold

remains cold so the plastic solidifies almost as soon as the mold is filled.

INJECTION MOLDING CYCLE

The sequence of events during the injection mold of a plastic part is called the injection moldingcycle. The cycle begins when the mold closes, followed by the injection of the polymer into the moldcavity. Once the cavity is filled, a holding pressure is maintained to compensate for material shrinkage. Inthe next step, the screw turns, feeding the next shot to the front screw. This causes the screw to retract asthe next shot is prepared. Once the part is sufficiently cool, the mold opens and the part is ejected.

Although most injection molding processes are covered by the conventional process description above,there are several important molding variations including:

Co-injection (sandwich) molding Fusible (lost, soluble) core injection molding Gas-assisted injection molding In-mold decoration and in mold lamination Injection-compression molding Insert and outsert molding Lamellar (microlayer) injection molding Low-pressure injection molding Metal injection molding Microinjection molding Microcellular molding Multicomponent injection molding Multiple live-feed injection molding Powder injection molding Push-Pull injection molding Reaction injection molding Resin transfer molding Rheomolding
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Structural foam injection molding Structural reaction injection molding Thin-wall molding Vibration gas injection molding Water assisted injection molding Rubber injection Injection_molding_of_liquid_silicone_rubber

PROCESS TROUBL ESHOOTI NG

Optimal process settings are critical to influencing the cost, quality, and productivity of plastic injectionmolding. The main trouble in injection molding is to have a box of good plastics parts contaminated withscrap. For that reason process optimization studies have to be done and process monitoring has to take

place. First article inspection of internal and external geometry including imperfections such as porositycan be completed using Industrial CT Scanning a 3D x-ray technology. For external geometry verificationonly a Coordinate-measuring machine or white light scanner can be used.

To have a constant filling rate in the cavity the switch over from injection phase to the holding phase can be made based on a cavity pressure level.Having a stable production window the following issues are worth to investigate:

The Metering phase can be optimized by varying screw turns per minute and backpressure.Variation of time needed to reload the screw gives an indication of the stability of this phase.

Injection speed can be optimized by pressure drop studies between pressure measured in the Nozzle (alternatively hydraulic pressure) and pressure measured in the cavity. Melted material with alower viscosity has less pressure loss from nozzle to cavity than material with a higher viscosity. Varyingthe Injection speed changes the shear rate. Higher speed = higher shear rate = lower viscosity. Payattention increasing the mold and melt temperature lowers the viscosity but lowers the shear rate too.

Gate seal or gate freeze / sink mark / weight and geometry studies have the approach to prevent sink marks and geometrical faults. Optimizing the high and duration of applied holding pressure based on cavity pressure curves is the appropriate way to go. The thicker the part the longer the holding pressure applied. The thinner the part the shorter the holding pressure applied.

Cooling time starts once the injection phase is finished. The hotter the melted plastics thelonger the cooling time the thicker the part produced the longer the cooling time.

MOLDING TRIAL

When filling a new or unfamiliar mold for the first time, where shot size for that mold isunknown, a technician/tool setter usually starts with a small shot weight and fills gradually until the moldis 95 to 99% full. Once this is achieved a small amount of holding pressure will be applied and holding

time increased until gate freeze off (solidification time) has occurred.

Gate freeze off time can be determined by increasing the hold time and then weighing the partwhen the weight of the part does not change we then know that the gate has frozen and no more materialis injected into the part. Gate solidification time is important as it determines cycle time and the qualityand consistency of the product, which itself is an important issue in the economics of the production

process.
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Holding pressure is increased until the parts are free of sinks and part weight has been achieved.Once the parts are good enough and have passed any specific criteria, a setting sheet is produced for

people to follow in the future. The method to setup an unknown mold the first time can be supported byinstalling cavity pressure sensors. Measuring the cavity pressure as a function of time can provide a goodindication of the filling profile of the cavity. Once the equipment is set to successfully create the molded

part, modern monitoring systems can save a reference curve of the cavity pressure. With that it is possibleto reproduce the same part quality on another molding machine within a short setup time.

MOLDING DEFECTS

Injection molding is a complex technology with possible production problems. They can be caused either by defects in the molds or more often by part processing (molding)

MoldingDefects

Alternativename

Descriptions Causes

Blister BlisteringRaised or layeredzone on surface ofthe part

Tool or material is too hot, often caused by a lackof cooling around the tool or a faulty heater

Burn marksAir burn/gas

burn/dieseling

Black or brown burntareas on the partlocated at furthest

points from gate orwhere air is trapped

Tool lacks venting, injection speed is too high

Color streaks(US) Colour streaks(UK) Localized change ofcolor/colour

Masterbatch isn't mixing properly, or the material

has run out and it's starting to come through asnatural only. Previous colored material"dragging" in nozzle or check valve.

Delamination

Thin mica like layersformed in part wall

Contamination of the material e.g. PP mixed withABS, very dangerous if the part is being used fora safety critical application as the material hasvery little strength when delaminated as thematerials cannot bond

Flash BurrsExcess material inthin layer exceedingnormal part geometry

Mold is over packed or parting line on the tool is

damaged, too much injection speed/materialinjected, clamping force too low. Can also becaused by dirt and contaminants around toolingsurfaces.

Embedded Embedded Foreign particle Particles on the tool surface, contaminated
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contaminates particulates (burnt material orother) embedded inthe part

material or foreign debris in the barrel, or toomuch shear heat burning the material prior toinjection

Flow marks Flow linesDirectionally "offtone" wavy lines or

patterns

Injection speeds too slow (the plastic has cooled

down too much during injection, injection speedsmust be set as fast as you can get away with at alltimes)

Jetting

Deformed part byturbulent flow ofmaterial

Poor tool design, gate position or runner.Injection speed set too high.

Knit lines Weld lines

Small lines on the

backside of core pinsor windows in partsthat look like justlines.

Caused by the melt-front flowing around anobject standing proud in a plastic part as well as atthe end of fill where the melt-front comestogether again. Can be minimized or eliminatedwith a mold-flow study when the mold is indesign phase. Once the mold is made and the gateis placed, one can minimize this flaw only bychanging the melt and the mold temperature.

Polymerdegradation

Polymer breakdownfrom hydrolysis, oxidation etc.

Excess water in the granules, excessivetemperatures in barrel

Sink marks [sinks]Localized depression(In thicker zones)

Holding time/pressure too low, cooling time tooshort, with sprueless hot runners this can also becaused by the gate temperature being set too high.Excessive material or thick wall thickness.

Short shot Non-fill / Shortmold

Partial partLack of material, injection speed or pressure toolow, mold too cold, lack of gas vents

Splay marks Splash mark /Silver streaks

Circular patternaround gate caused

by hot gas

Moisture in the material, usually whenhygroscopic resins are dried improperly. Trappingof gas in "rib" areas due to excessive injectionvelocity in these areas. Material too hot.

Stringiness StringingString like remainfrom previous shottransfer in new shot

Nozzle temperature too high. Gate hasn't frozenoff
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Voids

Empty space within part (Air pocket)

Lack of holding pressure (holding pressure isused to pack out the part during the holding time).Filling too fast, not allowing the edges of the partto set up. Also mold may be out of registration(when the two halves don't center properly and

part walls are not the same thickness).

Weld lineKnit line / Meldline / Transferline

Discolored linewhere two flowfronts meet

Mold/material temperatures set too low (thematerial is cold when they meet, so they don't

bond). Point between injection and transfer (to packing and holding) too early.

Warping Twisting Distorted part

Cooling is too short, material is too hot, lack ofcooling around the tool, incorrect watertemperatures (the parts bow inwards towards thehot side of the tool) Uneven shrinking betweenareas of the part

Methods such as industrial CT scanning can help with finding these defects externally as well asinternally.

TOLERANCES AND SURFACES

Molding tolerance is a specified allowance on the deviation in parameters such as dimensions, weights,shapes, or angles, etc. To maximize control in setting tolerances there is usually a minimum andmaximum limit on thickness, based on the process used. Injection molding typically is capable oftolerances equivalent to an IT Grade of about 9 14. The possible tolerance of a thermoplastic or athermoset is 0.008 to 0.002 inches. Surface finishes of two to four microinches or better can beobtained. Rough or pebbled surfaces are also possible.

Molding Type Typical [in] Possible [in]

Thermoplastic 0.008 0.002

Thermoset 0.008 0.002

LUBRI CATION AND COOLI NG

Obviously, the mold must be cooled in order for the production to take place. Because of the heatcapacity, low cost, and availability of water, water is used as the primary cooling agent. To cool the mold,water can be channeled through the mold to account for quick cooling times. Usually a colder mold ismore efficient because this allows for faster cycle times. However, this is not always true becausecrystalline materials require the opposite: a warmer mold and lengthier cycle time.
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POWER REQUIREM ENTS

The power required for this process of injection molding depends on many things and varies betweenmaterials used. Manufacturing Processes Reference Guide states that the power requirements depend on"a material's specific gravity, melting point, thermal conductivity, part size, and molding rate." Below is atable from page 243 of the same reference as previously mentioned that best illustrates the characteristicsrelevant to the power required for the most commonly used materials.

Material Specific gravity Melting point (F)

Epoxy 1.12 to 1.24 248

Phenolic 1.34 to 1.95 248

Nylon 1.01 to 1.15 381 to 509

Polyethylene 0.91 to 0.965 230 to 243

Polystyrene 1.04 to 1.07 338

I NSERTS

Metal inserts can also be injection molded into the workpiece. For large volume parts the insertsare placed in the mold using automated machinery. An advantage of using automated components is thatthe smaller size of parts allows a mobile inspection system that can be used to examine multiple parts in adecreased amount of time. In addition to mounting inspection systems on automated components,

multiple axial robots are also capable of removing parts from the mold and place them in latter systemsthat can be used to ensure quality of multiple parameters. The ability of automated components todecrease the cycle time of the processes allows for a greater output of quality parts.

Specific instances of this increased efficiency include the removal of parts from the moldimmediately after the parts are created and use in conjunction with vision systems. The removal of parts isachieved by using robots to grip the part once it has become free from the mold after in ejector pins have

been raised. The robot then moves these parts into either a holding location or directly onto an inspectionsystem, depending on the type of product and the general layout of the rest of the manufacturer's

production facility. Visions systems mounted on robots are also an advancement that has greatly changedthe way that quality control is performed in insert molded parts. A mobile robot is able to more preciselydetermine the accuracy of the metal component and inspect more locations in the same amount of time as

a human inspector.

Blow molding (also known as blow moulding or blow forming ) is a manufacturing process bywhich hollow plastic parts are formed. In general, there are three main types of blow molding: extrusion

blow molding, injection blow molding, and stretch blow molding. The blow molding process begins withmelting down the plastic and forming it into a parison or preform. The parison is a tube-like piece of

plastic with a hole in one end in which compressed air can pass through.
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The parison is then clamped into a mold and air is pumped into it. The air pressure then pushesthe plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the

part is ejected.

TYPOLOGI ES OF BL OW M

polymer and composite materials study materials

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