Temperature Dependence of Shear Modulus, Density, and Crystallinity of Isotactic Poly Polypropylene

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Abstract
Experiments were undertaken to determine the dependence of the shear modulus upon the density and degree of crystallinity of two samples of isotactic polypropylene over a range of temperatures. Annealing the polypropylene samples was found to increase both the shear modulus and the density. Both quantities appeared to be inversely related to the molecular weight of the two polypropylene samples investigated. These phenomena are similar to those observed for polyethylene in our earlier studies. On the other hand, the variation of crystallinity with temperature, as measured by changes in density and by x-ray diffraction, was not the same in polypropylene as in linear polyethylene.