ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A general criterion for craze formation is presented. Crazes are deformation zones that are common to both glassy and semicrystalline polymers. Crazes are composed primarily of fibrils. This paper attempts to describe the process that transforms unoriented glassy and semicrystalline polymeric solids into a fibrous state. The criterion for crazing discussed is a local phase transition. The transition occurs at the draw temperature. Unoriented solid-phase macromolecules, at local high-stress regions, undergo a transition to the elastomeric phase. Rapid extension and accompanying resolidification produce the fibrous morphology of craze fibrils. Cavitation of the deforming rubber phase ocurs because the local length increase is riot compensated for by an overall area decrease. Craze formation in glassy polymers has long been suspected to involve a local solid-to-rubber phase change. To relate crazes in glassy and semicrystalline polymers, one can assume that a solid-to-rubber phase change is required to produce craze fibrils in semicrystalline polymers. The transient melt phase would undergo rapid elongation, causing the formation of extended chain crystallites. These subsequently nucleate the remaining melt, which then crystallizes epitaxially as lamellae. Crystallization during flow would, therefore, be the mechanism of fiber formation.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760221207
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