In situ reactive compatibilization of PS/PMMA blends using SMA as compatibilizer: Effect of composition on structural, thermal and mechanical properties

This study elucidates in situ reactive compatibilization of polystyrene (PS) and polymethyl methacrylate (PMMA) blends using styrene-maleic anhydride (SMA) as a compatibilizer and benzoyl peroxide (BPO) as a free-radical initiator. Various PS/PMMA blends with weight ratios of 90/10, 80/20 and 70/30 were melt-processed using a co-rotating twin-screw extruder, incorporating 5, 7 and 10 wt.% SMA to evaluate the effects of composition and compatibilizer loading on blends' performance. Reactive compatibilization with 7 wt.% SMA 90/10 PS/PMMA composition significantly enhanced tensile strength (up to ∼25%), impact strength (by ∼30%), and heat deflection temperature (up to ∼11%), compared with uncompatibilized blends of same composition, owing to improved interfacial adhesion and refined phase morphology. FTIR and DSC analyses confirmed improved interfacial interactions whereas, TGA demonstrated enhanced thermal stability, with the onset degradation temperature (T _onset ) increased by ∼20°C. A 7 wt.% SMA threshold was identified for optimal properties, beyond which agglomeration adversely affected performance. A compatibilization model based on various reactions has been proposed that explains enhanced mechanical and thermal properties particularly in the presence of benzoyl peroxide acting as a free-radical initiator.