Pyrolysis characteristics and thermal kinetics of expanded polystyrene(EPS) and styrene-methyl methacrylate(St-MMA) copolymer in LFC process

The pyrolysis behaviors of foam patterns have critical influences on fluid morphology and defect formation in Lost Foam Casting(LFC). The pyrolysis behaviors of expanded polystyrene(EPS) and styrenemethyl methacrylate(St-MMA) foams were compared using synchronous thermal analysis(STA), which was performed under argon atmosphere at different heating rates(from 10 to 40 K·min~()). The degradation heat was calculated by integrating DSC curves. Results show that the calculated degradation heat of St-MMA(605.28 J·g) was significantly lower than that of EPS(706.71 J·g). Furthermore, the non-isothermal iso-conversional method was used to determine the pyrolysis apparent activation energies of EPS and St-MMA, and results show that the activation energy of St-MMA(200.36 kJ·mol) was apparently higher than that of EPS(167.92 kJ·mol). These calculated results indicate that the weight loss rate of EPS is greater than St-MMA in the pyrolysis process. In addition, the apparent activation energies at various pyrolysis stages demonstrate that the pyrolysis reactions of EPS and St-MMA may involve physical and chemical changes in the decomposition layer of the LFC process.