Preparation And Properties Of Flame Retardant Polysiloxane Modified Polycarbonate

Polycarbonate(PC)has good impact resistance,transparency and low water absorption,and is easy to process and modify.It is widely used in many fields such as electronics,architecture,vehicles,aircraft,medical products and so on.Many use scenarios urgently need to maintain PC materials with high transparency,high impact resistance in low temperature environment and high flame retardant grade,which is also a problem that researchers have been tackling.Polydimethylsiloxane(PDMS)is inherently flame retardant.Polycarbonate polysiloxane block copolymer(Si-PC)prepared by copolymerization of PC and PDMS can realize the good dispersion of PDMS in PC matrix.It not only has good flame retardancy,but also has the advantages of improving the low-temperature toughness of materials and maintaining good transparency,which has attracted the attention of the majority of researchers.In this paper,PC/Si-PC series materials were prepared by blending Si-PC with PC with three different PDMS block polymerization degrees and contents.The effects of PDMS block polymerization degrees and contents on the heat resistance,flow,transparency,mechanics and flame retardancy of PC/Si-PC materials were studied.Subsequently,PC/Si-PC-28/phosphazene materials with high transparency,high impact resistance in low temperature environment and high flame retardant grade were prepared through the compound flame retardant of PDMS and Hexaphenoxy cyclotriphosphazene(HPCTP).The effect of the amount of phosphazene on the properties of PC/Si-PC-28/phosphazene materials was studied,and the flame retardant mechanism of PDMS and its compound flame retardant mechanism with phosphazene were explored.The structural characterization of Si-PC by NMR,FT-IR and GPC showed that the polymerization degrees of PDMS blocks were 28,91 and 40 respectively,which were recorded as Si-PC-28,Si-PC-91 and Si-PC-40 respectively,and the PDMS blocks contained were recorded as PDMS-28,PDMS-91 and PDMS-40 respectively.The heat resistance of PC/Si-PC is slightly lower than that of PC,and the effect on transparency is Si-PC-28<Si-PC-91<Si-PC-40.The tensile and bending properties of PC/Si-PC are slightly lower than those of PC;The addition of Si-PC greatly improves the impact toughness of PC,especially at low temperature.The main toughening mechanism is cavitation matrix forced high elastic deformation mechanism.The polysiloxane phase domain sizes of PDMS-28,PDMS-91 and PDM-40 in PC matrix are about 25 nm,45 nm and 70 nm.PDMS can improve the flame retardant performance of PC,among which PDMS-40 and PDMS-28 have significant improvement effects.Compared with PC/Si-PC-28,the heat resistance of PC/Si-PC-28/phosphazene material is significantly lower,the fluidity is improved,and the light transmittance is slightly improved,which can be attributed to the plasticization of phosphazene.The phosphazene contains benzene ring,which is well dispersed in the matrix and has little effect on the bending and impact properties at room temperature.The impact strength decreased obviously at-40 ℃,but it still had excellent impact resistance when 3 phr and 4 phr of phosphazene were added.Phosphazene and PDMS have good compound flame retardant effect.Adding 4 phr or more of Phosphazene,the flame retardant grade of UL94 is increased to 1.5mm V-0.HPCTP not only plays a role in the solidified phase,but also releases gaseous products containing N and P,which has a flame retardant effect.PDMS is mainly flame retardant in solidified phase.During combustion,PDMS will migrate to the surface of carbon layer and finally form a high-density oxygen isolation and thermal insulation carbon layer rich in Si,O and P.