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Article
Hierarchical structure gradients developed in injection-molded PVDF and PVDF--PMMA blends. I. Optical and thermal analysis
Journal of Applied Polymer Science
  • Y. D. Wang
  • Mukerrem Cakmak
Document Type
Article
Publication Date
5-9-1998
Abstract
The structural gradients developed along and across the flow direction of injection-molded PVDF and PVDF/PMMA parts were investigated by optical microscopy and thermal analysis techniques. The spatial variation of crystallinity across the thickness direction was found to be insensitive to the process variables: injection speed and mold temperature. This relatively flat crystallinity profile across the thickness of the parts was found to decrease with the increase of PMMA concentration. The blends become noncrystallizable beyond about 40–45% PMMA concentration. The influence of flow history on the structural evolution across the thickness was observed in the peak position of the cold crystallization region. This peak temperature showed a minimum at depths where shear effects are at their maximum. This was attributed to the increased levels of chain orientation frozen in the amorphous portions of these regions which crystallize at lower temperatures upon heating.
Citation Information
Y. D. Wang and Mukerrem Cakmak. "Hierarchical structure gradients developed in injection-molded PVDF and PVDF--PMMA blends. I. Optical and thermal analysis" Journal of Applied Polymer Science Vol. 68 Iss. 6 (1998) p. 909 - 926
Available at: http://works.bepress.com/mukerrem_cakmak/112/