新型侧基含磷共聚酯的阻燃和热降解动力学

利用动态热重分析法(TG)研究了聚酯(PET )及侧基含磷共聚酯(FR-PET)在不同升温速率下的热稳定性及热降解动力学, 并通过极限氧指数法(LOI)考察了FR-PET的阻燃性能; 采用Flynn-Wall-Ozawa方法分析了PET和FR-PET的热降解表观活化能; 利用Coast-Redfern方法通过对不同机理模型的选取, 确定了PET和FR-PET热降解动力学机理及其模型, 得出了主降解阶段的非等温动力学方程及热降解速率曲线图. 研究结果表明, 侧基含磷单元的引入提高了聚酯的阻燃性能, 侧基上的P—C和P—O键易断裂, 从而降低了聚酯的热稳定性. PET和FR-PET的热降解表观活化能(0.1≤α≤0.85)分别为194-227和184-209 kJ/mol; PET和FR-PET热降解反应均属于受减速形α-t曲线控制的反应级数机理, 其机理函数为f(α)=3(1-α)2/3(0.1≤α≤0.85). 侧基含磷单元的引入对PET的主降解阶段的热降解速率并无实质上的影响. 侧基含磷共聚酯的凝聚相阻燃作用有限, 可能以气相阻燃机理为主发挥阻燃作用.

Flame Retardant and Thermal Degradation Kinetics of Novel Copolyester Containing Phosphorus Linked Pendant Groups

Thermal stability and thermal degradation kinetics of poly(ethylene terephthalate)(PET) and flame retardant copolyester(FR-PET) containing phosphorus linked pendant groups were investigated by a conventional dynamic thermogravimetric analysis(TG) under highly purity N2 atmosphere at different heating rates between 10 and 40 K/min and the flame retardant of PET and FR-PET were studied by limiting oxygen index(LOI) method. The thermal degradation activation energy of PET and FR-PET were determined by using Flynn-Wall-Ozawa method. The thermal degradation kinetic mechanism and models of PET and FR-PET were determined by the selection of different mechanical models, by which the isothermal kinetic equations and thermal degradation velocity curves of the main degradation process were obtained. The flame retardant of PET by incorporation of phosphorus unit linked pendant groups was improved. The degradation of FR-PET was determined by the breaking of P—C and P—O bonds, and thermal stability of FR-PET was lower than that of PET. Thermal degradation activation energies of PET and FR-PET were in the range of 194—227 kJ/mol and 184—209 kJ/mol(0.1≤α≤0.85), respectively. The solid-state decomposition mechanism of PET and FR-PET corresponded to the controlled decelerating α-t curve, a reaction order mechanism and the mechanism functions f(α) were 3(1-α)2/3(0.1≤α≤0.85).The thermal degradation velocity of the main degradation process of PET and FR-PET were near. Flame retardant mechanism of novel copolyester phosphorus containing linked pendant groups was most likely through the gas phase rather than the condensed phase.