PET-PTT共聚酯的热降解行为

Thermal Degradation of Poly(ethylene-co-trimethylene terephthalate) Studied by Py-GC/MS

采用热失重分析(TGA)和裂解气相质谱(Py-GC/MS)研究不同组成的PET(聚对苯二甲酸乙二醇酯)-PTT(聚对苯二甲酸丙二醇酯)共聚酯的热降解行为,并与PET和PTT均聚物作了比较.TGA结果表明,PET-PTT共聚酯的热稳定性介于均聚物PTT与PET之间,并随PET组分的增加而提高.利用Py-GC/MS得到PET-PTT共聚酯及均聚物的裂解产物的结构及分布,探讨PTT降解机理,并推测PET-PTT共聚酯的可能降解过程.发现PET-PTT共聚酯分解过程中产生了不同于PET和PTT裂解产物的组分,但不同组分的含量很小,这可能是由共聚酯中PTT(PET)序列长度较短所致.PET-PTT共聚酯在裂解过程中比PET和PTT均聚物产生了更多的挥发性产物.当PTT(PET)在共聚酯中的摩尔分数增大时由该链段降解产生的产物质量分数相应提高.

The degradation behavior of poly （ethylene-co-trimethylene terephthalate） （PET- PTT） was investigated by means of TGA and Py- GC/MS and the results were compared with those of PET and PTT. It has been found from TGA that the thermostability of PET- PTT was intervenient between PET and PTT, and improved with the increasing PET component. The distribution and molecular structure of gaseous pyrolysis products of PET- PTTs, PET and PTT were obtained from Py- GC/MS. Based on the degradation mechanism of PET, the processes of the degradation of PTT and PET- PTT copolyesters were described. It was found something different from both PET and PTT homopolymers yielded in the degradation process would present in the pyrolysates of PET- PTT copolyesters. However, the composition of the deviation was minor potentially because of the short molecular sequence length of PET or PTT. The PET- PTT copolyesters yielded more volatile products than PET and PTT homopolymers. Moreover, the higher content a component in the copolyesters, the higher amount of relative pyrolysates of that component appeared.