Thermal degradation kinetics of rigid polyurethane foams blown with water

摘要

The thermal decomposition behavior of rigid polyurethane foams blown with water was studied by dynamic thermogravimetric analysis (TGA) in both nitrogen and air atmosphere at several heating rates ranging from room temperature to 800 degrees C. The kinetic parameters, such as activation energy (E), degradation order (n), and pre-exponential factor (A) were calculated by three single heating rate techniques of Friedman, Chang, and Coats-Redfern, respectively. Compared with the decomposition process in nitrogen, the decomposition of foams in air exhibits two distinct weight loss stages. The decomposition in nitrogen has the same mechanism as the first stage weight loss in air, but the second decomposition stage in air appears to be dominated by the thermo-oxidative degradation. The heating rates have insig- nificant effect on the kinetic parameters except that the kinetic parameters at 5 C/min have higher values in nitrogen and lower values in air, indicating different degradation kinetics in nitrogen and air. The kinetic parameters of foam samples blown with different water level in formulation decline firstly and then increase when water level increases from 3.0 to 7.0 pph. According to the prediction for lifetime and half-life time of foams, water-blown rigid foams have excellent thermostability, when used as insulation materials below 100 degrees C. (c) 2006 Wiley Periodicals, Inc.