Journal
CRYSTAL GROWTH & DESIGN
Volume 17, Issue 4, Pages 1957-1965Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.cgd.6b01896
Keywords
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Funding
- Department of Science and Technology India [DST/1362]
- DST
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The effect of shear, shear history, and addition of poly(methyl methacrylate) (PMMA) in inducing the,beta-polymorph in poly(vinylidene fluoride) (PVDF) was investigated systematically for melt-mixed PVDF/PMMA blends. Various techniques-shch as polarized optical microscopy, (P0M) coupled' to a hot stage and a shear cell, Fourier transforrn, 'infrared spectroscopy (PTIR), differential thermal analysis, melt-theology, and dielectric relaxation spectroscopy were used to gain a mechanistic insight for the observed polymorphism in PVDF. Different PVDF tieli blends were prepared by melt-mixing and were subjected to different shear histories on a rheonieter, and the induction time was monitored with respect to PMMA content and,the applied shear flow in the blends. The rheological measurements= revealed that the induction time was 'significantly lower for blends with a higher PVDF content (>= 80 wt %), which was ascribed to the diluent effect of PMMA that restricts, the, chain mobility of PVDF and a Ionger,time is required to start the crystallization process. The crystalline, morphology observed from POM demonstrates that the growth rate of spherulites was greatly reduced with increasing PMMAI content in the blends., FTIR results were used to determine the amount of beta phase in the blends before and after the shear history. The blends'tliat were sheared at high temperature (220 degrees C) showed more beta phase than the blends that were sheared. around the crystallization temperature. This study clearly demonstrates the fact that shear, shear history, and the content of PMMA significantly influence the conformational change that results in phase transformation in PVDF. Further, this study will help guide researchers working on various aspects of polymer processing where-the, effect of blending and shear on polymorphism is very important.
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