Crystallization of poly(vinyl chloride) at high temperatures

A sample of poly(vinyl chloride) having a very good thermal stability and a high initial crystallinity was annealed between 80 and 260°C, either as it was or mixed with stabilizers, in sealed ampoules or in KBr pellets, and studied by X‐ray and IR techniques. When the sample is treated in glass ampoules, practically no changes in IR spectra are observed up to 240°C; the X‐ray diagrams, however, show an increase in the size of the crystallites but no increase in the amount of crystalline material. The melting point is observed by X‐ray between 250 and 260°C. If the sample is heated in the KBr pellets, it undergoes some stress which causes an increase of the crystalline IR bands at 604 and 635 cm −1 , but no change in the X‐ray diagram. At higher temperatures, dehydrochlorination is enhanced by the KBr and involves chiefly the amorphous regions.