The effect of an organophosphonite antioxidant on poly(ether ether ketone)/poly(ether imide) blend as studied by quasi-isothermal modulated differential scanning calorimetry and dynamic mechanical thermal analysis methods

In the present study, the effect of P-EPQ, an organophosphonite antioxidant, on the glass transition and the viscoelastic behavior of optimized poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI; PEEK/PEI: 50/50) blend has been reported. For this, P-EPQ was added in various proportions to the PEEK/PEI blend and was studied by quasi-isothermal modulated differential scanning calorimetry (Qi-MDSC) and dynamic mechanical thermal analysis (DMTA) methods. The Qi-MDSC results clearly indicate a significant decrease in the glass transition temperature of the blend up to 1 wt% P-EPQ addition. The DMTA measurements revealed a decrease in tan delta peak temperature upon antioxidant addition in agreement with calorimetric results. The shift factors obtained using the time-temperature superposition of DMTA data exhibit Williams-Landel-Ferry behavior, and the fractional free volume of the blend increases with increase in antioxidant addition (up to 1 wt%). The master curve of storage modulus predicts high modulus for the blend with 1 wt% antioxidant, revealing its suitability for high-impact applications.