Drawing of β-Crystal Nucleator-Added PP

Abstract

Abstract Extruded sheets were prepared from homo-isotactic poly-propylenes (PP) with 0 to 10 ppm of quinacridonequinone which is a β-crystal nucleator for PP and the characteristics of drawing behavior and properties of drawn sheets were studied. The sheet without the nucleator consisted of usual α-crystals (hereinafter called α-PP), whereas the sheets with the nucleator contained much β-crystals (hereinafter called β-PP), whose content slightly increased with increasing nucleator content. While the tensile yield stress of the β-PP is lower than that of the α-PP, the drawing stress of the former is higher than that of the latter at the higher strain region after yielding. Even after drawn, the β-crystals remain in the α-crystals with low crystallinity at low drawing temperatures. However, the β-crystals and amorphous phase gradually decrease with increasing drawing temperature, and the α-crystals dominate above 80°C. The resultant tensile modulus and strength of the drawn sheets show maxima at drawing temperatures of 40 to 80°C on a balance between the effects of crystallinity and molecular orientation. The tensile modulus and strength of drawn sheet prepared from the β-PP are higher than those prepared from the α-PP by about 10% at those temperatures. The tensile elongation of drawn sheet prepared from the β-PP is slightly higher than that prepared from the α-PP at low drawing temperatures due to the remained β-crystals.