Drawing of beta-crystal nucleator-added PP

Extruded sheets were prepared from homo-isotactic polypropylenes (PP) with 0 to 10 ppm of quinacridonequinone which is a beta-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 alpha-crys tals (hereinafter called alpha-PP), whereas the sheets with the nucleator c ontained much beta-crystals (hereinafter called beta-PP), whose content sli ghtly increased with increasing nucleator content. While the tensile yield stress of the PPP is lower than that of the alpha-PP, the drawing stress of the former is higher than that of the latter at the higher strain region a fter yielding. Even after drawn, the beta-crystals remain in the alpha-crys tals with low crystallinity at low drawing temperatures. However the beta-c rystals and amorphous phase gradually decrease with increasing drawing temp erature, and the alpha-crystals dominate above 80 degrees C. The resultant tensile modulus and strength of the drawn sheets show maxima at drawing tem peratures of 40 to 80 degrees C on a balance between the effects of crystal linity, and molecular orientation. The tensile modulus and strength of draw n sheet prepared from the beta-PP are higher than those prepared from the a lpha-PP by about 10% at those temperatures. The tensile elongation of drawn sheet prepared from the beta-PP is slightly higher than that prepared from the alpha-PP at low drawing temperatures due to the remained beta-crystals .