Morphology development and exclusion of noncrystalline polymer during crystallization in PVDF/PMMA blends

摘要

Morphology development during the crystallization of poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blends was investigated at various crystallization temperatures (T-C) by means of time-resolved light scattering measurements and atomic force microscopy (AFM). A coarse spherulite obtained at a high T-C of 162 degrees C was found to be developed with a two-step crystallization process The ordering in the spherulites (Pr) increased with time at the early stages and then decreased at the later stages. The rate of spherulite growth started to decrease when Pr started to decrease In contrast, in the compact spherulite obtained at a low T-C of 148 degrees C, Pr decreased monotonously with time while the growth rate was constant. AFM observation revealed that such characteristic crystallization behavior is attributed to the exclusion of PMMA from the crystal growth during the crystallization, ie, the amount of excluded PMMA becomes larger as the distance from the spherulite center increases and the crystallization temperature rises.