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The effect of Ca/Zn stabilizers on the thermooxidative degradation poly(vinyl chloride) /chlorinated polyethylene blends

Abstract

Termooksidacijska razgradnja mješavina poli(vinil-klorida) (PVC) i polimernoga modifikatora kloriranoga polietilena (CPE) istraživana je metodama diferencijalne pretražne kalorimetrije i termogravimetrije u dinamičkim i izotermnim uvjetima. Ustanovljeno je da istraživani sastavi mješavina PVC-a i CPE-a (sadržaja klora 42 %) nisu mješljivi. U temperaturnom području od 50 do 650 ºC termooksidacijska razgradnja mješavina zbiva se kroz dva temeljna razgradna stupnja. U prvome, do 400 ºC, osnovne reakcije su dehidrokloriranje PVC-a i CPE-a, premda se brzine i mehanizam razgradnje polimera znatno razlikuju. Istraživan je utjecaj Ca/Zn karboksilata različitih omjera kalcija i cinka na toplinsku postojanost komponenata mješavine. Ca/Zn karboksilati stabiliziraju PVC mijenjajući mu brzinu i mehanizam razgradnje, ali istodobno utječu i na razgradnju polimernoga modifikatora CPE-a.The thermooxidative degradation of blends of poly(vinyl chloride) (PVC) and polymeric modifier chlorinated polyethylene (CPE) was investigated by means of differential scanning calorimetry (DSC) and thermogravimetry (TG) under dynamic and isothermal conditions. The immiscibility of PVC and CPE (chlorine content 42 %) was established for all the investigated compositions of the blends. The thermooxidative degradation of PVC/CPE blends in temperature range of 50 – 650 ºC occurs in two basic degradation steps. In the first, up to 400 ºC, the main degradation reactions are dehydrochlorination of PVC and CPE, but the rates and mechanisms of the polymer degradation are significantly different. The influence of Ca/Zn carboxylates with different Ca/Zn ratios, on thermooxidative stability of the blends components was also investigated. Ca/Zn carboxylates stabilize PVC by changing its degradation rate and mechanism, but, at the same time, these stabilizers influence the degradation of the polymeric modifier CPE

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