Directional solidification of isotactic and atactic polypropylene blends

The directional solidification of polypropylene (PP) films results in an oriented semicrystalline microstructure and may offer a method to improve the properties of a product. The directional solidification of isotactic PP samples blended with 0% to 50% atactic PP, by mass, was therefore studied. The effects of composition and processing conditions were monitored to determine how they affect the quality and microstructure of the directionally solidified films. Difficulty was encountered in reproducing testable samples with a unidirectional crystal microstructure. Tensile testing of directionally solidified films was used to quantify the yield strength and elastic modulus of the films. These properties were compared with those of other PP films. The tensile test results do not support the hypothesis that enhanced mechanical properties were produced by directional solidification of the PP films. Improving the sample fabrication method and optimizing the processes involved may, however, lead to directionally solidified PP films with enhanced mechanical properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1516–1528, 2000