Composition optimization of PEEK/PEI blend using model-free kinetics analysis

We report here the investigations on the thermal and thermo-oxidative degradation kinetics of a miscible high performance polymer blend poly(ether ether ketone)/poly(ether imide) (PEEK/PEI) with various compositions, measured in argon and air medium, respectively. The derivative thermogravimetric results indicate two-stage decomposition for both thermal and thermo-oxidative degradation for the entire composition of PEEK/PEI blend. Interestingly, the PEI addition is found to enhance the thermo-oxidation rate of PEEK. The effective activation energy (Eα) as a function of conversion (α) is found for both the processes using model-free kinetics. The model-free kinetics results reveal that the blend with 50% PEI content show high Eα value and the differential scanning calorimetry results corroboratively show a significant change in crystallinity for this PEI composition. Based on these results, the blend with composition 50/50 (PEEK/PEI) is suggested to have optimum thermal stability.