PET/SiO_2纳米复合材料的内耗研究

INTERNAL FRICTION STUDIES ON PET AND PET/SiO_2 NANOCOMPOSITES

利用内耗和DSC的方法研究了不同纳米粒子含量PET/SiO2纳米复合材料和纯PET弛豫性能的变化,并计算出次级弛豫峰的激活能和峰高以及主级弛豫的激活参数和峰高.结果发现内耗峰的峰高和主弛豫的激活参数以及次级弛豫的激活能随纳米SiO2的增加而减小.一方面内耗峰的峰高主要是PET的非晶区的分子链或基团运动产生,因此纳米粒子的高效成核效应,促进PET结晶成核,非晶区减小,导致内耗峰减小.另一方面由于纳米粒子与PET产生化学接枝以及氢键等作用,对链段的运动起到了一定的限制作用,导致主弛豫的激活参数和次级弛豫的激活能的增加.因此纳米SiO2颗粒与PET基体之间的化学和物理相互作用导致了PET链段的弛豫特性的变化.

The relaxation behavior of neat PET and PET/SiO2 nanocomposites was investigated by using methods of internal friction and DSC.The activation energy of β relaxation was calculated by Arrhenius equation because it was a Debye peak,but the α relaxation didn’t follow the Arrhenius equation,so its activation parameter was calculated by VFT equation.The heights of the α and β peaks were obtained by the results of internal friction measurements.The results showed that the heights of peak,activation parameters of the α relaxation and activation energy of the β relaxation increased with increasing the content of filler.On one hand,SiO2 nanoparticles had grafting reaction with carboxyl,so the motion of polymer chains and groups was more and more difficult with increasing the content of filler.On the other hand,the nanoparticles acted as nucleating point,so they could promote the nucleation and crystallization of PET, and the amorphous regions decreased.The peak heights of the α and β relaxations were related to the normal amorphous regions,so both of them obviously decreased with increasing the content of filler.Hence the relaxation properties of PET chains and groups were changed by addition of SiO2 nanoparticles.