Preparation And Toughening Modification Of PC/PMMA Alloy With High Hardness

Polycarbonate(PC)has a low surface hardness which limits its application in some fields.The blends of PC and polymethyl methacrylate(PMMA)have the advantages of high surface hardness and high gloss.In order to obtain a higher surface hardness,the content of PMMA in blend generally needs to be high,resulting in a sharp decrease in the in toughness of blend.Therefore,in this paper,the toughening modification of PC/PMMA has been studied.In this paper,MBS,the core-shell polymer,was used as a toughening agent,and PC/PMMA/MBS blends were prepared by once extrusion and secondary extrusion.The effects of processing method and the addition of MBS on the microstructure,surface hardness and mechanical properties of the blends were studied.Furthermore,the PC/PMMA/MBS compatibilized using SAN-g-MAH as a compatibilizer and the flame retardant modification using DBDPO as a flame retardant.The results show when the ratio of the PC/PMMA was 80/20,the surface hardness could reach 3 H,but the impact strength is only 13.6 KJ/m2.After the addition of MBS,the surface hardness of the PC/PMMA blend also remained 3 H.Compared to PC/PMMA,the impact strength of PC/PMMA/MBS blends prepared by once extrusion did not change significantly.In the PC/PMMA/MBS blends prepared by secondary extrusion,when the amount of MBS added to 6.5 Phr,the impact strength was significantly increased to 66.4 KJ/m2,but the elongation at break improved slightly.The results of scanning electron microscopy show there was no significant difference in the size and dispersion of the PMMA dispersed phase in the blends by using once extrusion and secondary extrusion.In this study,the toughening mechanism of MBS was proposed.In the PC/PMMA/MBS blends prepared by once extrusion,MBS is mostly distributed in the PC phase and PMMA was a role of rigid particles,so toughness did not improve significantly.But in the PC/PMMA/MBS blends prepared by secondary extrusion,MBS is mostly distributed in the PMMA phase and the toughness of the PMMA phase was improved,thereby enhancing the toughening of the blends.The study also found that the addition of MBS could reduce the balance torque and improve the processing fluidity.The results of GPC show that,even after secondary extrusion,the molecular weight of PMMA phase is only slightlydecreased.The addition of SAN-g-MAH to the PC/PMMA/MBS blend resulted in a significant increase in the elongation at break and a slight increase in impact strength.Moreover,the tensile and flexural strength remained stably.But the surface hardness decreased slightly with the increased of SAN-g-MAH.DSC test show that the compatibilizer SAN-g-MAH could improve the compatibility of PC and PMMA.The rheological results show that the viscosity of the material decreased gradually and the flowability improved.The flame retardant modification of PC/PMMA/MBS was modificate by DBDPO,with the increase of DBDPO,the bending and tensile strength of the blends remained stably,and the impact strength and surface hardness decreased.When DBDPO was 8phr,the horizontal combustion level of the blend reached I level and when DBDPO was 6phr,the vertical burning level of the blend could reach the standard,V-0.With the increase of DBDPO,the carbon layer covered by the surface after combustion gradually increased,the structure of the carbon layer was denser.Moreover,the maximum decomposition temperature was mareased.