| Polycarbonate /Acrylonitrile-Butadiene-Styrene(PC/ABS) has the largest yield in the engineering plastics. With the increasing application range of PC/ABS blends, the multifunction and high performance of PC/ABS blends are critical. Therefore, the development and research of the toughener which has the capacity of halogen-free flame retardant and high tougheness could have many important implications.In this paper, a traditional emulsion polymerization method had been used to synthesis the polysiloxane core latex with the choice of three siloxane monomers octamethylcyclotetrasiloxane(D4), methacryloxy propyl trimethoxyl silane(KH-570) and hexamethyl disiloxane(MM). N-butyl acrylate(BA) and methyl methacylate(MMA) as the shell monomers had been grafted polysiloxane core latex to prepare the polysiloxane-acrylate copolymers with core-shell structure.This composite latex were synthesized via multi-stage emulsion polymerization which the mean particle diameter was 193.8 nm and has a higher solid content of 40%. After the process of demulsification, curing, vacuum filtering, washing and drying,the final product polysiloxane-acrylate elastomer present a kind of white solid particles. The structure of the polysiloxane-acrylate and the morphologies of the latex particles were characterized by the FT-IR, TGA, TEM and laser grain-size analyzer.Each reaction time of three stages had been confirmed via testing the solid content and monomer conversation, and the results showed that the optimal reaction time of synthesizing the polysiloxane core latex was 3 h, grafting BA and MMA both were 2.5 h.The effects of the monomer ratio, emulsifier concentration, and water-soluble initiator amounts on the state of the polysiloxane-acrylate latex and particle diameters were also studied. The results showed that the optimal amounts of the emulsifier dodecyl benzenesulfonic acid(DBSA) accounted for 1.4 wt% of total amount of water in the emulsion system, the best dosage of the water-soluble initiator potassium persulfate(K2S2O8) for 0.36 wt% of the total monomers, and the best monomer proportion of the silicone monomer and the acrylate monomer was 5:5. The solvent acetone and methanol alcohol were used to extract the final product, demonstrating that the grafting degree was 79.8% and the grafting efficiency was 48.9%.The core-shell polysiloxane-acrylate elastomer was used for PC/ABS blends toughening modification, compared with the common toughener MBS resin. The effects of kinds and the levels of the toughener on the mechanical properties and the flame retardancy of the PC/ABS blends were investigated. When 5.0 % polysiloxane-acrylate elastomer and MBS resin were added to the PC/ABS blends respectively, the notched impact strength of the blends increased not obviously. With the amount 14.0 wt% of phosphate flame retardants tetraphenly bispheol A diphosphate(BDP), the flame retardancy of the blends improved dramatically with the LOI of the blends reached 26.9 % and flammability achieved UL94 V-0@3.2 mm.While the notched impact strength of the blends declined sharply to 12.7 k J/m2 as the BDP added in the blends. MBS resin and BDP additive were used to improve the notched impact strength to 52.2 k J/m2.While polysiloxane-acrylate elastomer combining with BDP, the notched impact strength of the blends improved to 44.9 k J/m2 and the LOI of the PC/ABS blends achieved 26.4%.Above all, the polysiloxane-acrylate elastomer synthesized in the experiment could improve efficiently the notched impact strength of the PC/ABS blends especially in the flame-retardant system and be a well performing toughener in the plastic alloys... |
PDF Full Text Request