A survey is given of the recent advances in the study of and the present knowledge of the thermal degradation of polyvinyl chloride. The sites for initiation of the thermal degradation, the mechanism of the dehydrochiorination, the discolouration of PVC by heat and the influence of plasticizers on the rate of degradation are discussed.

No abstract

No abstract

A B S TRA C T:Poly(vinylch1oride) (PVC)was mixed with various poly(methacry1ate)s. poly(carb0nate)s and polymers containing nitrile groups (poly(acrylonitrile), poly(styreneco-acrylonit r i l e ) , nitrile rubber, hydrogenated nitrile rubber) a n d / o r C -C double bonds ( n i t r i l e rubber, high-impact poly(styrene)). The thermal stability was measured a t 180 OC in nitrogen, and the evolved HC1 was d e t e c t e d by conductometry.I t is shown that t h e n a t u r e of the e s t e r group and the content of nitrile groups and C-C double bonds a r e t h e dominating f a c t o r s for the thermal stability of poly(vinylchloride) in these blends. An influence of t h e miscibility of PVC with the various blend components on t h e t h e r m a l stability can not b e c l e a r l y detected.Differential scanning calorimetry (DSC) was used a s a powerful method to study the stabilizer distribution of heterogeneous PVC/poly(styrene-co-acrylonitrile) and PVC/poly(methylacrylate) blends. It is shown that the stabilizer can be solubilized either in t h e PVC phase (PVC/poly(methylacrylate)) or in both phases of t h e blends PVC/poly(styrene-co-acrylonitrile)).

The commercial stabilizers Ca‐Zn stearate and dibutyltin‐S,S′‐di(isooctyl thioglycolate) have been investigated as photostabilizers for rigid poly(vinyl chloride) (PVC) in the presence of two types of CaCO3 as filler (natural and modified). The results reveal the costabilizing efficiency of CaCO3, especially the natural type, when it is used in concentrations of 1–30% by weight. The stabilizing efficiency of CaCO3 is indicated by the longer induction period and the lower rate of dehydrochlorination. The stabilizing effect of CaCO3 may be attributed because of its opacity and action as a screening agent by reflecting ultraviolet light, thereby hindering the penetration of the light into the polymer matrix. In addition, CaCO3 has the ability to absorb the HCl evolved during processing. The slight difference in the stabilizing effect of natural CaCO3 compared to that of the modified one can be attributed to the modification process, that may decrease the number of active sites on the surface of CaCO3, that in turn are responsible for the absorption of the evolved HCl. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers