Preparation and application in toughening poly(butylene terephthalate) resin of poly(BA/MMA) core-shell structured copolymer

In recent years, research on emulsion polymerization used for modification of brittle polymers has been taken more and more seriously. A series of latex of poly(butyl acrylate/methyl methacrylate) core-shell polymer (PBM) with the different core-shell ratio were produced by seed emulsion polymerization and redox initiator system. The overall conversion of the monomers reaches up to 99.75% and almost all the instantaneous conversions are over 92%. The latex particle size (d_z) is 353.3 nm and the polydispersity index (PDI) less than 0.075. The experimental values of particle sizes are in accordance with theoretical calculating values, which show that the particles have grown without significant secondary nucleation. When the modifier (core-shell ratio 75/25) is used, the phenomenon of brittle-ductile transition and the Charpy notched impact strength of poly(butylene terephthalate) (PBT)/PBM (100/20) reaches its maximum value, increased to 8.63 times compared with pure PBT resin, and the tensile strength keeps the high values. Dynamic mechanical analysis(DMA) spectra show that the internal friction peak of the rubber phase moves to high temperature and the internal friction peak of PBT to low temperature; at the same time, the mechanical loss peak becomes wider. These results show that the compatibility of PBM particles with PBT matrix reaches the best when the modifier (core-shell ratio of 75/25) is used. The SEM observation explains the mechanical results.