ORIENTED GAMMA-ISOTACTIC POLYPROPYLENE CRYSTALLIZED AT ATMOSPHERIC-PRESSURE

A method for crystallizing oriented samples of the gamma-phase of isot actic polypropylene (iPP) under atmospheric pressure in the presence o f nucleating fibers has been developed. The technique uses iPP grades of high molecular weight and high isotacticity and produces a mixture of alpha and gamma-phase crystals within the matrix of both pitch-base d carbon and Kevlar(R)-reinforced composites. Two-dimensional wide-ang le X-ray scattering (WAXS) patterns from these samples show that the c ontent of the gamma-phase decreases as the fiber loading in the compos ites decreases, suggesting that the gamma-phase is directly nucleated by the fibers. (C) 1998 John Wiley & Sons, Inc.