X-RAY AND OPTICAL STUDIES OF THE EFFECT OF ORIENTATION OF THE ALPHA MECHANICAL LOSS MECHANISM OF POLYETHYLENE.
MASSACHUSETTS UNIV AMHERST POLYMER RESEARCH INST
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The alpha mechanical loss of low density polyethylene has been previously studied by the dynamic x-ray diffraction technique and has been shown to result, in part, from the rotation of crystals about their b-axes. This presumably is due to the twisting motion of lamellae in the equatorial regions of spherulites. The intensity of this loss increases up to about 10 strain and subsequently decreases. The dynamic birefringence changes primarily arise from this phenomena and also exhibit a similar change in intensity with strain. While both dynamic x-ray diffraction and dynamic birefringence measurements are possible for low-density polyethylene, experimental limitations permit only the birefringence measurements for high density polyethylene. The increase in loss intensity with strain at low strains is attributed to the increase in lamellae mobility associated with the splaying apart of lamellae within the deformed spherulite. The subsequent decrease in mobility with further strain is associated with the decrease in crystal mobility associated with the extension of tie chains between crystallites in the strained polymer. Author