聚酯的热分析与热分解动力学的研究

Thermal Analysis and Thermal Decomposition Kinetics of Polyester

基于热分析动力学理论,在单一升温速率下采用差示扫描量热法（DSC）和热重分析（TG）对两种PET（a-PET和b-PET）试样在空气中的热解过程进行研究。通过考察DSC曲线得到两种PET的玻璃化转变温度（Tg）、熔点（Tm）、结晶温度（Tc）和结晶度等,得到结果：a-PET和b-PET的玻璃化转变温度分别为80.70℃和93.81℃,熔点分别为261.41℃和260.31℃,结晶温度分别为128.28℃和229.59℃,结晶度分别为27.76%和31.17%。通过Freeman_Carroll方法计算不同试样各阶段热解反应的活化能、反应级数和指前因子。结果表明：PET有两个主要的热解阶段,第一阶段在340-445℃温度区间中,a-PET的活化能、反应级数和指前因子分别为141.00 kJ·mol^-1和0.65、4.97E＋9 min^-1;b-PET的活化能、反应级数和指前因子分别为167.128 kJ/mol、0.39和4.33E＋11 min^-1;第二阶段在515-561℃温度区间内,a-PET的活化能、反应级数和指前因子分别为106.48 kJ/mol、0.66和2.2E＋6 min^-1;b-PET的活化能、反应级数和指前因子分别为123.04 kJ/mol,0.70和1.05E＋7 min^-1。

Based on thermal analysis kinetics, differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） were employed to evaluate the thermal decomposition behaviors of two types of polyester（PET, a-PET and b-PET）, in air atmosphere at a single heating rate of 10℃· min^-1. The glass transition temperature（Tg）, melting point temperature（Tin）, crystal temperature （Tc）, crystallinity and some other parameters were obtained through DSC curves. The results are shown as follows： The T, of a-PET and b-PET is 80.70 ℃ and 93.81 ℃ , respectively; the Tm is 261.41℃ and 260.31℃, respectively; Tc is 128.28℃ and 229.59℃, respectively; and the crystallinity is 27.76% and 31.17%, respectively. Moreover, the kinetic parameters like activation energy, reactive index and pre-exponential factor were calculated and analyzed with Freeman-Carroll method in every decomposition stage, respectively. The conclusions can be deduced that there are two main decomposition stages in different temperature sectors of thermal decomposition. The activation energy, reactive index and pre-exponential factor of a-PET are respectively 141. 00 kJ/mol, 0.65 and 4.97E ＋ 9 min^-1; and those of b-PET are 167.13 kJ/mol, 0.39, 4.33E ＋ 11 min ^-1 individually during the first stage （ 340- 445 ℃ ） of thermal decomposition. In the second stage（515-561 ℃ ） of thermal decomposition, the activation energy, reactive index and pre-exponential factor of a-PET are 106.48 kJ/mol 0.66 and 2.2E ＋ 6 min ^-1, respectively; and those of b-PET are 123.04 kJ/mol, 0.70, 1.05E ＋ 7 min ^-1 individually.