Effect of reactive compatibilization on the properties of poly(butylene terephthalate)/acrylonitrile–ethylene–propylene–diene–styrene blends

Blends of poly(butylene terephthalate) (PBT) with 30 wt % acrylonitrile–ethylene–propylene–diene–styrene (AES) were prepared with methyl methacrylate (MMA)/glycidyl methacrylate (GMA)/ethyl acrylate (EA) terpolymers (MGEs) as compatibilizing agents. These acrylic terpolymers were miscible with the styrene–acrylonitrile (SAN) phase of AES, whereas the epoxide groups of GMA could react with the PBT end groups; this could lead to the formation of grafted copolymers (PBT‐g‐MGE) at the PBT/AES interface during the melt processing of the blends if at least a fraction of this interface was formed between the PBT and SAN phases. This study found evidence of the aforementioned interfacial structure through the effectiveness of the MGE terpolymers in promoting the compatibilization, as evaluated by dynamical mechanical analysis, through the increase in the viscosity of the blends, and through the reduction of the AES particle size dispersed in the PBT matrix. These effects became more intense with an increase in the overall concentration of GMA in the blends and with a reduction of the molecular weight of MGE. Another effect promoted by the compatibilization was a remarkable reduction of the brittle–ductile transition temperatures of the blends, which was correlated with the reduction of the AES particle size. However, this correlation between the brittle–ductile transition temperatures and particle size did not hold for the blend with the lowest AES particle size, which showed a high ductile–brittle transition temperature. These mechanical behaviors were examined on the basis of the current theory of the toughening of thermoplastics, which takes into account the importance of the rubber interparticle distance and the cavitation process of these particles.