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UDKUDKUDKUDK 678.744678.744678.744678.744 :::: 66.095.26-911.4866.095.26-911.4866.095.26-911.4866.095.26-911.48 :::: 541.64541.64541.64541.64 ==== 111111111111 ScientificScientificScientificScientific paperpaperpaperpaper

GRAFTGRAFTGRAFTGRAFT COPOLYMERIZATIONCOPOLYMERIZATIONCOPOLYMERIZATIONCOPOLYMERIZATIONOFOFOFOF ACRYLATEACRYLATEACRYLATEACRYLATE ANDANDANDANDMETHACRYLATEMETHACRYLATEMETHACRYLATEMETHACRYLATEMONOMERSMONOMERSMONOMERSMONOMERSWITHWITHWITHWITH POLY(VINYLPOLY(VINYLPOLY(VINYLPOLY(VINYL CHLORIDE)CHLORIDE)CHLORIDE)CHLORIDE) ININININ

EMULSIONEMULSIONEMULSIONEMULSION

LjubiLjubiLjubiLjubiššššaaaa NikoliNikoliNikoliNikolićććć1111,,,, DraganDraganDraganDragan JovanoviJovanoviJovanoviJovanovićććć2222,,,, VesnaVesnaVesnaVesna NikoliNikoliNikoliNikolićććć1111&&&&AgneAgneAgneAgnešššš KaporKaporKaporKapor33331Faculty of Technology, Leskovac, Serbia,2Hanplast, Žitoradja, Vladičin Han, Serbia

3Faculty of Science, Institute of Physics, Novi Sad, Serbia

A direct graft copolymerization of poly (vinyl-chloride) (PVC) was carried outby using two monomers: n-butyl methacrylate and iso-butyl acrylate.Copolymerization was carried out in the emulsion with dioctyl sodium sulfosuccinateused as an emulgator, in the quantity above the critical mycelial concentration, at 80º Cand with benzoyl peroxide. The graft copolymer obtained was extracted by ethylacetate in order to remove the molecules of homopolymer which originated from themonomer used in the comopolymerization reaction and then characterized by infra redspectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction(XRD). FT-IR spectra of a graft copolymer prove the existence of groups of monomersused in copolymerization, which point to the achieved copolymer synthesis. The resultsshow that the sample crystallinity decreases with the increase of the quantity of graftmonomers. DSC curves show that the copolymer glass transition temperature decreasesin relation to the pure poly (vinyl-chloride)- the higher content of a graft monomerleads to the larger decrease. Depending on the relative elongation, the curves of stressprove that n-butyl methacrylate and iso-butyl acrylate graft with PVC increases thevalue of the elongation of samples.

IntroductionIntroductionIntroductionIntroduction

Poly(vinyl chloride) (PVC) is one of the very used polymers and it is producedall over the world in enormous quantities due to its good physical properties. However,its disadvantages are poor plasticity and low thermal stability and these shortcomingsare moderated by adding plasticizers, thermal stabilizers, lubricants, fillers, and otherpolymers. This fault of poly(vinyl chloride) can be eliminated by copolymerizationwith other monomers, or by subsequent graft copolymerization of the poly(vinylchloride) [1, 2]. For graft copolymerization, PVC can be dehydrogenated, and thencopolymerized by radical mechanism [3 - 6]. A number of examples of direct emulsionand suspension copolymerization of vinyl chloride and other monomers are present inthe literature: ethylene [7], propylene [8], 1,3-butadiene [9], styrene [10], allyl chloride[11], vinylidene chloride [12], allyl acetate [13], vinyl acetate [14, 15], acrylonitrile [16,17], acrylic acid [18], 2-ethylhexyl acrylate [19], methyl acrylate [20], acrylamide [21],methacrylic acid and methyl methacylate [22], glycidyl methacrylate [23], maleic

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anhydride [24], N-vinyl pyrolidone [25] etc. The purpose of this paper is to carry outthe graft polymerization of acrylate and mathacrylate monomers with poly(vinylchloride) without dehydrochlorination.

ExperimentalExperimentalExperimentalExperimentalMaterialsMaterialsMaterialsMaterialsPoly(vinyl chloride) (Sigma-Aldrich, Wisconsin)iso-Butyl acrylate (Sigma-Aldrich, Wisconsin)n-Butyl methacrylate (Sigma-Aldrich, Wisconsin)Dioctyl sodium sulfosuccinate (Sigma-Aldrich, Wisconsin)Benzoyl peroxide (Sigma-Aldrich, Wisconsin)

SynthesisSynthesisSynthesisSynthesis procedureprocedureprocedureprocedureThe copolymerization was completed in water emulsion with the emulgator dioctylsodium sulfosuccinate in quantities above the critical mycelial concentration at 80oC.Benzoyl peroxide was used as the radical formation instigator. The monomers wereapplied in various ratios (20, 40 and 60%) to PVC. Synthesized graft copolymersundergo Soxlet extraction with ethyl acetate in order to extract homopolymer, whichwas dissoluble in ethyl acetate and then dried at 100°C.

CharacteriazationCharacteriazationCharacteriazationCharacteriazation ofofofof graftgraftgraftgraft copolymerscopolymerscopolymerscopolymers

InfraInfraInfraInfra redredredred spectroscopyspectroscopyspectroscopyspectroscopy withwithwithwith FourierFourierFourierFourier transformationtransformationtransformationtransformation (FT-IR)(FT-IR)(FT-IR)(FT-IR)FTIR spectra of the samples were recorded in KBr pellet (0.6 mg sample, 140 mg KBr)in the range of wavelengths from 4000 to 400 cm-1 on a Bomem Hartmann&BraunMB-series FTIR spectrophotometer.

DifferentialDifferentialDifferentialDifferential scanningscanningscanningscanning calorimetrycalorimetrycalorimetrycalorimetry (DSC)(DSC)(DSC)(DSC)DSC curves of the samples were recorded on a DuPont DSC differential scanningcalorimeter with the scanning rate of 10oC/min in the temperature range from 30 oC to280oC in closed aluminum pans in nitrogen atmosphere.

X-RayX-RayX-RayX-Ray diffractiondiffractiondiffractiondiffraction (XRD)(XRD)(XRD)(XRD)X-ray diffraction was performed on a Phillips X'Pert powder diffractometer under thefollowing conditions: samples were exposed to monochrome CuK α radiation(λ=1,54178 Ǻ) and analyzed under angle 2θ between 5 and 65o with 0.05o incrementsand recording time, τ=5 sec. The voltage and the strength of the electric current were40 kV and 20 mA, respectively.

MechanicalMechanicalMechanicalMechanical propertiespropertiespropertiesproperties

Breaking strain and relative breaking elongation were measured on a homemade breaking apparatus at Čerprom, Aleksinac. The samples were 100 mm in length.

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30 mm wide and 2 mm in thickness. The initial operation length of the samples was 30mm.

ResultsResultsResultsResults andandandand discussondiscussondiscussondiscusson

Poly(vinyl chloride) reaction with radicals R • is followed by making aradical center in the polymer chain capable of reacting with the monomerpresent in the reaction mixture. Once a monomer molecule reacts with theradical center in poly(vinyl chloride) chain, other monomer molecules continueadding thus making a side chain. To achieve the effective reaction the effectivemixing is needed and dioctyl sodium sulfosuccinate supplement enables a betterwetting of solid poly(vinyl chloride) with a liquid monomer.Figure 1 shows a reaction scheme of the graft copolymerization poly(vinyl chloride)and n-butyl methacrylate .Graft copolymerization reaction of poly(vinyl chloride) and iso-butyl acrylate areshown in Figure 2.

CH2 CH CH2

Cl

CH CH2

Cl

CH

Cl

R CH2 CH CH2

Cl

CH CH2 CH

Cl

R+ Cl

CH2 CH CH2

Cl

CH CH2 CH

Cl+ H2C C C

OO (CH2)3CH3

CH2 CH CH2

Cl

CH CH2 CH

Cl

C CO

O (CH2)3CH3

CH2

CH3

H3C

Poly(vinyl chloride) Poly(vinyl chloride) radical

n-Butyl methacrylate

Poly(vinyl chloride-g-n-butyl methacrylate)Figure 1. Graft copolymerization poly(vinyl chloride) and n-butyl methacrylate

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CH2 CH CH2

Cl

CH CH2

Cl

CH

Cl

R CH2 CH CH2

Cl

CH CH2 CH

Cl

R+ Cl

CH2 CH CH2

Cl

CH CH2 CH

Cl+ CH2 CH C

OO CH

CH2CH3

CH3

CH2 CH CH2

Cl

CH CH2 CH

Cl

CH CO

O CHCH2CH3

CH3

CH2

Poly(vinyl chloride) radicalPoly(vinyl chloride)

iso-Butyl acrylate

Poly(vinyl chloride-g-iso-butyl acrylate)

Figure 2. Graft copolymerization reaction of poly(vinyl chloride) and iso-butyl acrylate

FT-IR spectra of poly(vinyl chloride) and graft copolymer poly(vinyl chloride-g-n-butyl methacrylate) with 20% of n-butyl methacrylate and 20% of iso-butylacrylate are shown in Figures 3 and 4, respectively. FT-IR spectra of graft copolymershow a strong band at about 1730 cm-1 originating from C=OC=OC=OC=O valence vibrations frommonomers used for grafting copolymerization, n-butyl methacrylate and iso-butylacrylate. Poly(vinyl chloride) has no C=OC=OC=OC=O group so there is no band in this frequencyarea . In graft spectra there are also strong bands at 1158.14 cm-1 (in spectrumpoly(vinyl chloride-g-n-butyl methacrylate) (Figure 3) and at 1168.12 cm-1 (inspectrum poly(vinyl chloride-g-iso-butyl acrylate) (Figure 4), originationg fromvalence vibration of a C-O-CC-O-CC-O-CC-O-C group of aliphatic esters not present in the poly(vynylchloride) molecule structure.

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Figure 3. FT-IR spectra of poly(vinyl chloride) and graft copolymer poly(vinylchloride-g-n-butyl methacrylate) with 20% of n-butyl methacrylate

FIgure 4. FT-IR spectra of poly(vinyl chloride) and graft copolymer poly(vinylchloride-g-iso-butyl acrylate) with 20% iso-butyl acrylate

There is no significant difference in the recorded diffractograms of poly(vinylchloride) and graft copolymers poly(vinyl chloride-g-n-butyl methacrylate) andpoly(vinyl chloride-g-iso-butyl acrylate) (Figures 5 i 6). The poly(vinyl chloride)sample give a wide peak at 2θ=8,2; 16,6; 18,8; 24,4; i 40,0 ° . Generally, the sample

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crystallinity decreases with the increase of the quantity of grafted monomer. DSCcurves confirm that the copolymer glass transition temperature is smaller incomparison to the pure poly(vinyl chloride) (Figures 7 i 8). Exothermal peaks on DSCcurves of graft copolymers (curves 2 to 7) at about 130 to 170 °C originate, mostprobably, from the grafted copolymer acrylate segments crosslinking with PVC.Namely, the literature gives a description of heating poly(vinyl chloride) above 100°Cwhich makes the polymer degrade and emit HCl [26]. HCl that catalyzes theelimination of HCl from the next monomer unit, resulting in the rapid unzipping offurther acid to give polyene sequences. The polyenes undergo secundary reaction suchas crosslinking [26].

Figure 5. X-ray powder diffraction patterns of poly(vinyl chloride) (1), graft copolymerpoly(vinyl chloride-g-n-butyl methacrylate) with 20% (2), 40% (3) and 60% (4) n-butyl methacrylate

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Figure 6. X-ray powder diffraction patterns of poly(vinyl chloride) (1), graft copolymerpoly(vinyl chloride-g-iso-butyl acrylate) with 20% (5), 40% (6) and 60% (7) iso-butylacrylate

Stress-strain curves (Figure 9) show that graft copolymers poly(vinyl chloride-g-n-butyl methacrylate) gave greater values for material strength and elongation values,while graft copolymers poly(vinyl chloride-g-iso-butyl acrylate) gave greaterelongation values but the breaking strength was reduced. The strength of PVC wasincreased by n-butyl methacrylate, while copolymerization of PVC with iso-butylacrylate gave PVC the plasticity and enabled an easier polymer breaking.

247

Figure 7. DSC curves of poly(vinyl chloride) (1), graft copolymer poly(vinyl chloride-g-n-butyl methacrylate) with 20% (2), 40% (3) and 60% (4) n-butyl methacrylate

Figure 8. DSC curves of graft copolymer poly(vinyl chloride-g-iso-butyl acrylate) with20% (5), 40% (6) and 60% (7) iso-butyl acrylate

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Figure 9. Curves of stress vs. relative elongation for poly(vinyl chloride) (1), graftcopolymers poly(vinyl chloride-g-n-butyl methacrylate) with 20% (2), 40% (3) and60% (4), poly(vinyl chloride-g-iso-butyl acrylate) with 20% (5), 40% (6) and 60% (7)iso-butyl acrylate

Table 1. Breaking strain and relative elongation values for poly(vinyl chloride) andgraft copolymers

Polymer Breaking strain, N/mm2 Elongation, %Poly(vinyl chloride) 2.18 150Poly(vinyl chloride-g-n-butylmethacrylate) 20 %

2.63 370

Poly(vinyl chloride-g-n-butylmethacrylate) 40 %

3.20 302

Poly(vinyl chloride-g-n-butylmethacrylate) 60 %

3.14 273

Poly(vinyl chloride-g-iso-butylacrylate) 20 %

0.81 192

Poly(vinyl chloride-g-iso-butylacrylate) 40 %

0.83 222

Poly(vinyl chloride-g-iso-butylacrylate) 60 %

0.87 229

The FTIR analysis show that co-polymerization has been achieved by graftingn-butyl methacrylate and iso-butyl acrylate monomers into the synthesized poly(vinyl

249

chloride). The investigation of physical properties shows that the properties ofpoly(vinyl chloride) and graft copolymers poly(vinyl chloride-g-n-butyl methacrylate)and poly(vinyl chloride-g-iso-butyl acrylate) are different. Curves of stress vs. relativeelongation for poly(vinyl chloride) and graft copolymers also show that grafting of n-butyl methacrylate and iso-butyl acrylate monomers increases the elongation of thesamples thus improving the physical properties of poly(vinyl chloride).

LiteratureLiteratureLiteratureLiterature

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This paper was supported by Ministry of Science and Environmental Protection –Republic of Serbia, project TR-6708B.

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U ovom radu je izvedena direktna kalem kopolimerizacija poli(vinil-hlorida)(PVC) sa dva monomera: n-butil-metakrilatom i izo-butil-akrilatom. Kopolimerizacijaje izvedena u emulziji pri čemu je kao emulgator iskorišćen dioktil sulfo sukcinat ukoličini iznad kritične micelarne koncentracije, na temperaturi od 80 °C uz benzoil-peroksid. Dobijeni kalem kopolimer je ekstrahovan etil-acetatom da odstrani molekulehomopolimera nastalog od monomera koji je korišćen u reakciji kopolimerizacije, azatim okarakterisan infracrvenom spektroskopijom (FT-IR), diferencijalnomskenirajućom kalorimetrijom (DSC) i difrakcijom X-zraka (XRD). FT-IR spektrikalem kopolimera pokazuju prisustvo grupa iz monomera korišćenih ukopolimerizaciji, što ukazuje na ostvarenu sintezu kopolimera. Time je iskorišćenaosobina PVC-a da ima hlorov atom u svojoj strukturi koji se lako uključuje u prenosaktivnosti pri radikalnoj kopolimerizaciji. Rezultati pokazuju da opada kristaličnostuzoraka sa povećanjem količine kalemljenog monomera. DSC krive pokazuju da sesnižava temperatura staklastog prelaza kopolimera u odnosu na čist poli(vinil hlorid) ito sniženje je veće ukoliko je veći sadržaj kalemljenog monomera. Krive napona uzavisnosti od relativnog izduženja pokazuju da se kalemljenjem n-butil metakrilata iiso-butil akrilata sa PVC-om povećava vrednost elongacije uzoraka.