过氧化物动态硫化EPDM/PP热塑性弹性体的等温结晶行为

通过差示扫描量热分析法详细表征了PP、PP/过氧化物、EPDM/PP及过氧化物动态硫化EPDM/PP(TPV)的等温结晶行为。结果表明,与EPDM的简单共混既降低了PP的结晶速率也降低了PP的结晶度,过氧化物动态硫化后交联的EPDM颗粒作为异相成核剂,能大大提高PP的结晶速率但也严重地降低了PP的结晶度,TPV的Avrami指数为3.5,符合异相成核的三维球型生长方式。X射线衍射结果表明,4组样品的晶体结构完全相同,仍为α型单斜晶体。熔融曲线显示过氧化物/PP及TPV相比PP,在153℃出现额外熔融峰,PP原有的160℃熔融峰逐渐消失而153℃熔融峰强度逐渐增强且体系的结晶度逐渐降低。采用移动窗口二位相关红外对TPV熔融行为进行研究,发现153℃处的熔融峰对应于10个和5个单体单元螺旋序列结构,160℃时对应12个单体单元螺旋序列结构。较低的结晶温度有助于长螺旋序列结构的形成及PP结晶度的提高。

Isothermal Crystallization Behavior of EPDM/PP Thermoplastic Vulcanizates by Crosslinking of Peroxide

The isothermal crystallization behavior of PP,PP/peroxide,EPDM/PP and EPDM/PP thermoplastic dynamic vulcanizate (TPV) was characterized by DSC.The results show that the simple blending with EPDM reduces the crystallization rate and crystallinity of PP,the crosslinked EPDM particles using peroxide as heterogeneous nucleating agent greatly increase the crystallizing rate of PP but seriously reduced the crystallinity of PP.The Avrami index of TPV is 3.5,consistenting with the three-dimensional spherical growth of heterogeneous nucleation.X-ray diffraction shows that the crystal structures of the four samples are identical and remain the α-type monoclinic crystals.The melting curve shows that the peroxide/PP and TPV exhibit an additional melting peak at 153 ℃,the intensity of which increases gradually with rise of the crystallization temperature.The melting behavior of TPV was studied by moving window two related infrared,and the melting peak at 153 ℃ corresponds to hdical sequence structures of 10 and 5 monomeric units and at 160 ℃ corresponds to helical sequence structures of 12 monomeric units.The low crystallization temperature contributes to formation of the long helical sequence structure and improvement of the crystallinity of PP.