长链支化聚丙烯的反应挤出制备及其流变和热力学性能研究

在过氧化引发剂和季戊四醇三丙烯酸酯(PETA)存在下，采用反应挤出法制备了长链支化聚丙烯（LCB-PP）。用旋转流变仪和差示扫描热法系统研究了纯的和改性PP的流变性能和热力学性能，并考察了不同过氧化引发剂对改性PP的性能和支化情况的影响。研究发现，单纯使用过氧化引发剂改性时，PP以降解为主；加入多功能单体PETA后，PP以接枝反应为主。流变行为研究发现，过氧化引发剂/PETA改性的PP，其流变性能呈现如低频处储能模量增大，剪切变稀行为明显，损耗角随频率变化出现平台区，零剪切黏度增大等特点，证明改性PP存在长链支化结构，通过公式计算发现改性PP的支化度较高。差士扫描量热分析表明，过氧化引发剂/PETA改性PP的结晶温度高于纯PP，这也说明改性PP存在长链支化结构。同时发现过氧化引发剂/PETA改性PP时，过氧化引发剂结构对改性PP的流变性能、热力学性能和支化度影响较小。

Rheology and Thermal Properties of Long Chain Branching Polypropylene by Reactive Extrusion

Long chain branched polypropylene (LBPP) were prepared via reactive extrusion in the presence of pentaerythritol triacrylate (PETA) and a peroxide. The rheology and thermal properties of linear PP and modified LBPP were evaluated using rotational rheometer and differential scanning calorimetric (DSC). Moreover, the influence of the type of peroxide on the properties and branching degree of LBPP were also evaluated. LBPP exhibited a higher G’ at low frequency, lower Tan δ at low frequency, higher zero shear viscosity, and stronger shear shinning, which constituted the features of long branching. DSC determination showed that the crystallization temperature of LBPP was higher than that of linear PP. In addition, it was found that the type of peroxide did not significantly affect the thermal and rheological properties and branching degree of modified LBPP.