The microstructure of poly(vinyl chloride) as revealed by x‐ray and light scattering

Abstract

AbstractSmall‐angle x‐ray scattering (SAXS) and wide‐angle x‐ray scattering (WAXS) as well as small‐angle light‐scattering (SALS) techniques have been applied to investigate the microstructure of a number of commercial poly(vinyl chloride) (PVC) samples. From the wide‐angle x‐ray scattering, crystallinity and crystal size parameters have been determined. The crystallinity of the samples investigated range from 5% to 10%. Superstructure parameters such as crystallite thickness, distribution functions of crystallite and amorphous thicknesses, and size of ordered regions have been obtained by an analysis of the SAXS curves using the cluster model. The crystallinity agrees well with the WAXS crystallinities indicating that most of the crystals are lamellar shaped, though some rodlike entities are present in the sample as is shown by the small‐angle light scattering. From the SAXS analysis, the microstructure is described as clusters of lamella stacks which are identical with the subprimary particles. Their size is determined to be 220–240 Å. Emulsion type PVC also contains lamellar‐shaped crystals. The superstructure, however, of this type of PVC is different from that of mass or suspension‐polymerized material. The SAXS curve does not reveal any correlation between the crystals.