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 δ 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.