Comparison of x-ray diffraction and thermal analysis methods for assessing order in poly(vinyl chloride)

Thermal analysis and wide‐angle x‐ray diffraction were used to assess the crystallinity for a series of poly(vinyl chloride) (PVC) samples, and the use of two complementary techniques was found beneficial. Two polymers were studied; a commercial suspension grade PVC, and an experimental grade of higher syndiotacticity. Both were examined as powders, and after processing. All samples were also examined after heat treatment at various temperatures between 100 and 175°C. Annealing the suspension grade of PVC appeared to cause a small change in total crystallinity, but little change in crystallite size. When the low temperature powder was annealed, some increase in crystallinity was detected. However, when this polymer was milled, there was a significant increase in crystallite size, and crystallinity seemed to increase further. Particularly noticeable was the increase in the amount of high melting crystallites.