氟碳聚合物在高温下表面解聚速率常数的测定

Single Pulse Shock Tube Studies on the Decomposition of Fluoropolymers

聚四氟乙烯在高温受热条件下发生解聚,并件有单体C_2F_4的析出,单体继续发生化学反应。本文用激波管实验方法研究了半径为10μm和70μm聚四氟乙烯粉粒在温度为1400K至3300K,时间为500μs条件下解聚机理和表面解聚速率常数的测定,给出了解聚速率常数ω_s=1.6exp(-18400/RT)克·厘米^(-2)·秒^(-1)这一结果与Steg与Lew的理论结果相比,表现激活能小了一半,而在这一温度范围内,绝对速率小四至五个量级。分析了这两个结果的差异,指出对于高温、大样品、短时间尺度来说,扩散阻滞和逆向解聚起了重要作用。

This paper is concerned with the kinetics of thermal decomposition of polytetrafluroethylene at high temperature. Powder of spherical polytetrafluoroethylene, radius 10μm and 70μm are decomporsed in a single pulse shock tube with argon as working gas. The duration of the heating time is 500μs. The result is described as surface degradation rate constant.ω_s=1.6exp(-18400/RT)g·cm^(-2)·s^(-1)(1400K<T<3300K).This is quite different with theory given by Steg and Lew based on the experiment study of Madorsky et al. We have pointed that the difference are caused by the effects of diffusion process and reverse depolymerazation of the monomer in the specimen of our experiment as the temperature is high while the scale of specimen is large enough.