PET低温固相缩聚反应动力学

在烘箱中模拟干燥条件,研究了 PET 切片在115—190℃,0—11h 条件下的特性粘度的变化。结果表明,PET 切片在干燥条件下同时存在链增长和水解两个化学反应;温度≤130℃(时间≤3h)时,体系以酯键的水解反应为主;而温度>130℃时,则以链增长反应为主。PET 切片在低温(115—190℃)条件下的固相缩聚属于二级反应,影响链增长反应速度的主要原因是扩散过程,而温度对反应速度的影响很小。

DYNAMICS OF COLD SOLID-PHASE POLYCONDENSATION OF PET

Using fiber-grade PET chips with〔η〕0.655 and softening temperature 262.7℃ asmat-erials,in a drying oven under the reaction temperature 115-190℃ and reaction time 0-11 hours respectively,the variation of inherent viscosity is studied.The reactions weremainly involved in chain-extending and hydrolytic degradation.In this work,the appar-ent velocity constant and activation energy of chain-extending reaction were obtainedquantitatively.The resultss how:①when the temperature is less than or equal to 130℃,the molecular weight increases linearly after it decreases to the minimum as the increaseof reaction time.②when the temperature is more than 130℃,the molecular weight incr-eases linearly.It means that the main reaction in the system is hydrolytic degradation ofester bondand that when temperature over 130℃,the chain-extending is the main reac-tion.The solid-phase polycondensation of PET chips under low temperature is a two-orderreaction same as that occurs under high temperature.The diffusion of macromo-lecular chains has a great influence on the velocity of chain-extending,but there isalittle influence with temperature on the velocity.