Modification of the core–shell ratio to prepare PB-g-(MMA-co-St-co-GMA) particle-toughened poly(butylene terephthalate) and polycarbonate blends with balanced stiffness and toughness
Reactive polybutadiene-g-(methyl methacrylate-co-styrene-co-glycidyl methacrylate) particles with different core–shell ratios were prepared using a seeded emulsion polymerization method. The influence of the core–shell ratio on the toughness and stiffness of poly(butylene terephthalate) (PBT) and polycarbonate (PC) blends was investigated. A low core–shell ratio induced a higher grafting degree and ‘internal grafting’ which were useful for keeping the blend stiffness. A high core–shell ratio improved the soft rubber content and was beneficial for improvement of toughness. The optimum grafting degree region was 56–187% for the reactive core–shell (RCS) particles, in order to achieve good dispersion. The RCS-28 and RCS-37 particles were efficient at keeping a higher stiffness but lower toughening effect for PBT/PC blends due to their poor cavitation ability. RCS-73-toughened blends showed weak impact and yield strength due to their agglomeration morphology and high rubber phase content. In the present paper, PBT/PC/RCS-46 blends showed a better toughness and stiffness balance. When the RCS-46 content was 15%, an impact strength of 950 J m−1 and a yield strength of 50 MPa could be achieved for the PBT/PC/RCS-46 blend.