Morphologies, failure spherulitic

The effects of morphology (i.e., crystallization rate) (6,7, 8) on the mechanical properties of semicrystalline polymers has been studied without observation of a transition from ductile to brittle failure behavior in unoriented samples of similar crystallinity. Often variations in ductlity are observed as spherulite size is varied, but this is normally confounded with sizable changes in percent crystallinity. This report demonstrates that a semicrystalline polymer, poly(hexamethylene sebacate) (HMS) may exhibit either ductile or brittle behavior dependent upon thermal history in a manner not directly related to volume relaxation or percent crystallinity. 

Under long term stress conditions, in eithercyclic (fatigue) or static (creep) loadings, intrinsic morphological features can become areas of weakness, e.g., cracks can form in polyethylene at the boundaries of spherulites and within them, suggesting that long term failure is due to separation between lamellae. 

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