β晶型成核剂对聚丙烯结晶行为和力学性能的影响

Influence of β Nucleating Agent on Crystallization and Mechanical Properties of Polypropylene

以2,6-苯二甲酸环己酰胺(TMB-5)为β晶型成核剂,采用熔融共混的方法制备β晶改性聚丙烯.利用示差扫描量热仪、偏光显微镜、拉伸实验机以及冲击试验机对改性聚丙烯的微观结构、热性能、结晶性能、力学性能进行研究.实验结果表明,在聚丙烯中添加β晶型成核剂进行改性后,由于成核剂在体系中起到了异相成核的作用,聚丙烯中部分晶型由α晶型向β晶型转变,改性聚丙烯的结晶温度向高温方向移动,且聚丙烯球晶尺寸明显减小,球晶之间无明显的边界.随着β晶型成核剂含量的增加,改性聚丙烯的拉伸强度、弯曲强度和弯曲模量呈现先降后升的趋势,而其断裂伸长率和冲击强度呈先升后降的趋势,并且当β晶型成核剂含量为0.4份时,改性聚丙烯的拉伸强度、弯曲强度和弯曲模量为最小值,断裂伸长率和冲击强度达到最大值.

The modified polypropylene was prepared by melt blending of polypropylene （PP）, using N, N＇-Dicy- clohexylterephthalamide as a β nucleating agent, and its microstructure, mechanical property, thermal property and crystallization behavior were explored by Differential scanning calorimetry, Polarizing microscopy, tensile tester and pendulum impact testing machine, respectively. The results show that the addition of β nucleating agent results in the crystalline of PP transforming from α crystal toβ crystal and the crystallization temperature increases whilst β nucleating agent works as a mechanism of heterogeneous nucleation. Meanwhile, the spherulite sizes of PP decrease obviously and no boundary exists in the spherulites. The tensile sfrength, flexural strength and flexural modulus of modified PP firstly decrease and then increase, but the elongation at break and impact strength of modified PP go up and then decline when the feed content of β nucleating agent increases. Moreover, the tensile strength, flexural strength and flexural modulus of modified PP arrive at the lowest values, while its elongation at break and impact strength reach the maximum values when the content of βcrystal is 0.4 phr.