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
.