Plastic waste from electrical and electronic equipment is an increasing problem. Consequently, it is desirable to separate and recycle these plastics, especially high-value plastics, such as polycarbonate (PC). One of the concerns is enhancing the PC flame-retardant (FR) properties so it can be reused in equipment housings. Using data on potassium diphenylsulfone sulfonate (KSS), it is shown that the flame retardancy of recycled PC can be enhanced. One major advantage of KSS is that it is non-halogenated, playing an important role as the government eliminates potentially unhealthy halogenated FRs. Understanding the mechanism by which the KSS/PC system works has not been extensively studied. Mechanistic studies on the thermal degradation were performed on the PC/KSS FR system. Data were obtained by thermogravimetric analysis (TGA), TGA/Fourier transform infrared analysis, and TGA/gas chromatography-mass spectrometry. Results show that KSS acts as a catalyst in accelerating the disproportionation of bisphenol A and dimerization of isopropylphenol which leads to an enhanced carbonaceous char. This, in combination with CO2 production, leads to an intumescent char that accounts for PC/KSS's excellent FR ability. Using this knowledge on polycarbonate, basic kinetic parameters were backed out to be used in a mathematical model to predict heat release rate. Modeling heat release rate, as assessed by cone calorimetry, has not been extensively studied for char-forming polymers. A finite element model that considers the heat and mass transport phenomena taking place was developed, and this accurately predicts the heat release rate curve for char forming polycarbonate. This model is also applicable to other PC FR systems where only the pyrolysis kinetics is different.