Thermogravimetric analysis (TGA) of Raw-PS and HTT-PS were performed by the simultaneous Shimadzu D50 TGA/DTA analyzer illustrated in Figure 3-1. The samples were dried in an electric oven at 105 ˚C for 12 h to minimize the effect of the inherent moisture before starting the experiment. Approximately 10 mg of sample was loaded into an Al2O3 ceramic crucible with the particle size less than 250 μm. Air was constantly supplied at 150 ml/min and the test was done under the atmospheric pressure. The sample was heated from the room temperature to 850 ˚C at the heating rate of 5 ˚C/min to minimize the heat transfer limitation. The sample weight loss was continuously recorded as the function of time and temperature.