成型温度对β晶型聚丙烯冲击强度的影响

Effect of Processing Temperature on Impact Strength of β-PP

测定了两种含β晶聚丙烯(β-PP)在23、-20℃下的冲击强度,研究了β-PP 的冲击强度随成型温度的变化规律。结果表明,随着成型温度的上升,β-PP 在23℃下的冲击强度降低。成型温度为80℃时,-20℃下两种β-PP 的冲击强度均呈峰值,分别为3.8 kJ/m^2和3.2 kJ/m^2。差示扫描量热分析表明,随着成型温度的升高,β晶的含量先上升后下降,在100℃附近出现峰值,β晶含量为73%;β-PP 的冲击强度随成型温度变化的趋势与-20℃下的一致,此条件下为5.0 kJ/m^2。不同降温速率的非等温结晶实验结果表明,在降温速率为20℃/min 即样品结晶温度为117℃左右时,样品中β晶含量最大(58.7%)。

Effect of processing temperature on the impact strength at 23 ℃ and - 20 ℃ was studied for imtactic polypropylene containing β-nucleating agent. With increasing processing temperature, the im- pact strength at 23 ℃ decreased, but that at - 20 ℃ increased. When processing temperature increased from 80 ℃ to 100 ℃ , the impact strength at -20 ℃ increased from 3.8 kJ/m^2 to 5.0 kJ/m^2, which was attributed to a high content of β form crystals of 73 wt %, as revealed by DSC. In nonisothermal crystallization experiments, it was found that the cooling rate of 20 ℃/min resulted in a maximum con tent of β form crystals of 58.7 wt%, where the crystallization temperature was 117 ℃.