热处理条件对R-PET/LLDPE-g-MA共混物中PET玻璃化转变行为的影响

对回收聚对苯二甲酸乙二酯(R-PET)/LLDPE-g-MA马来酸酐改性的线性低密度聚乙烯共混物进行不同条件的热处理, 采用差示扫描量热仪(DSC)研究共混物基体PET的玻璃化转变行为. 结果表明, 当热处理温度低于PET的玻璃化转变温度(Tg)时, PET的玻璃化转变区域出现热焓松弛现象. 随着热处理温度的增加, PET的Tg逐渐升高; 在50~70 ℃下热处理48 h后, PET的Tg逐渐稳定. 当热处理温度高于PET的Tg而低于100 ℃时, PET的玻璃化转变区域出现2个热流转变, FTIR分析表明, PET分子构象开始发生变化. 当热处理温度为100 ℃时, DSC曲线上PET的玻璃化转变消失, PET的结晶度明显增加, 说明PET开始冷结晶的温度在90~100 ℃之间.

Effects of Annealing Condition on the Glass Transition Behavior of PET in R-PET/LLDPE-g-MA Blends

Effects of annealing temperature and annealing time on the glass transition of PET in the Recycle-polycethylene terephatalate(R-PET)/LLDPE-g-MA blends were investigated by DSC. The sub-Tg annealing leads to the enthalpy relaxation in the glass transition region of PET. The Tg of PET shifts to higher temperature with the increase of annealing temperature. The Tg of PET tends to be stable in the blends annealed at 50—70 ℃ for more than 48 h. After above-Tg annealing below 100 ℃, two heat flow transitions of PET appear around the Tg of PET. FTIR results show that molecular conformation of PET begin to change. However, the glass transition of PET disappears in the blend annealed at 100 ℃, and WAXD results show that the crystallinity of PET increases obviously, indicating that the Tcc,on of PET is between 90—100 ℃.