Directional solidification of isotactic and atactic polypropylene blends

The directional solidification of polypropylene (PP) films results in an or iented semicrystalline microstructure and may offer a method to improve the properties of a product. The directional solidification of isotactic PP sa mples blended with 0% to 50% atactic PP, by mass, was therefore studied. Th e effects of composition and processing conditions were monitored to determ ine how they affect the quality and microstructure of the directionally sol idified films. Difficulty was encountered in reproducing testable samples w ith a unidirectional crystal microstructure. Tensile testing of directional ly solidified films was used to quantify the yield strength and elastic mod ulus of the films. These properties were compared with those of other PP fi lms. The tensile test results do not support the hypothesis that enhanced m echanical 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 enha nced mechanical properties. (C) 2000 John Wiley & Sons, Inc.