Effect of Beta-nucleator on crystalline structure and mechanical properties of isotactic polypropylene

Abstract

ß structure (hexagonal) of isotactic polypropylene (PP) can be generated by an addition of ß nucleator. The nucleator used in this study is quinacridone (Permanent Red E3B). The samples are blended or mixed, by mechanical blending and internal mixing (masterbatch compounding). The PP-B nucleator blends are pelletizated by a twin-screw extruder and then compressed and extruded into films. The factors affecting structure and mechanical properties of polypropylene with nucleator including additive content, compounding and processing conditions are investigated in this study. Based on WAXD, DSC, polarizing optical microscope analysis results demonstrate that the compressed molded films, PP-quinacridone (0.0001% blended by mechanical blending) has the maximum ß content that is shown by the kx value of approximately 0.91 and PP-quinacridone (0.0001% blended by internal mixing) has the kx value of approximately 0.64. However, with lower ß-content but better ß crystal distribution, the latter condition gave rise to the highest elongation at break and toughness. In the case of extruded film, ß structure could not be generated and the smectic structures occur in extruded films. The two conditions producing extruded films with higher elongation and toughness than extruded PP were PP-quinacridone (0.0001 and 0.01 % blended by mechanical blending). Extruded PP film containing only 0.0001 % of quinacridone showed a significant improvement in oxygen permeation as compared to extruded PP film.