Inhibited transesterification on the properties of reactive core-shell particles toughened poly(butylene terephthalate) and polycarbonate blends

Reactive core-shell particles with polybutadiene as core (297 nm) and methyl methacrylate-co-styrene-co-glycidyl methacrylate terpolymer as shell (PB-g-MSG) were prepared to toughen poly(butylene terephthalate) (PBT) and polycarbonate (PC) blends. Sodium pyrophosphate (SPP) was used to modify the transesterification between PBT and PC. FTIR results proved the occurrence of the transesterification and the addition of SPP inhibited the exchange reactions. SEM displayed the PB-g-MSG particles dispersed in PBT/PC matrix uniformly and the addition of SPP had no negative influence on the uniform dispersion. The crystallization temperature of PBT increased with the addition of SPP which indicated the constraint of PC block on the crystallization of PBT chain became poor. At the same time, with the addition of SPP into the PBT/PC/PB-g-MSG blend, the T_g of PC phase further shifted to higher temperature. PB-g-MSG was an effective toughener for PBT/PC blends, however, SPP decreased the toughening efficiency of PB-g-MSG particles for the PBT/PC blends. The yield strength and tensile modulus of PBT/PC blends increased first and then deceased with the increase of SPP content in the blends. Fracture mechanisms results showed the addition of SPP was not beneficial to the cavitation of the core-shell particles and shear yielding of the matrix and led to the decreased impact toughness.