Preparation And Properties Of Organosilicon Flame Retardant PBT And Its Alloy

Polymer materials have unparalleled advantages compared with some traditional materials,moreover their alloys combine advantages of different materials.As a major member of engineering plastics,Poly(butylene terephthalate)(PBT)has been widely applied for industrial applications thanks to its attractive mechanical performance,dimensional stability,thermal properties and processing advantages.Bisphenol A polycarbonate(PC)and poly(butylene terephthalate)(PBT)are easily blended to form PC/PBT blends,exhibiting promising impact strength,workability,chemical resistance and excellent heat-resistance to be widely used in such fields as electrical and electronic devices,auto industry,and outdoor equipments.Nevertheless,the high flammability of neat PBT restricts its further usage in the wider scope of application.The utilization of traditional halogen-based flame retardants are restrained due to the release of the toxic and corrosive smoke during combustion.And the employment of common non-halogen flame retardant will greatly impair other key properties of PBT.Therefore,the development of novel halogen-free flame-retarded PBT and its alloy material has become the mainstream nowadays.The three main aspects of this dissertation are summarized below:Superfine high activity magnesium hydroxide as a carrier of special silicone-based flame retardant(FRX-210)was selected to prepare halogen-free flame retardant polybutylene terephthalate(PBT).Additionally,oxygen index analyzer and cone calorimeter was used to investigated the flame retardant effect on PBT when adding FRX-210,andcomplex containing FRX-210 and boron phosphate or phosphate flame retandant.The results showed that,FRX-210 can significantly increase the limiting oxygen index(LOI)of PBT,adding 30%FRX-210 can increase the LOI of PBT from 22.1%to 27.5%.Adding FRX-210 and boron phosphate complex into PBT can further increase LOI,adding 20%FRX-210 and 10%boron phosphate help the PBT LOI reached 36.0%.By using FRX-210,thermal degradationrate of PBT reduced ancd the amount of char residue increased.The addition of FRX-210 improved fire performance index,reduced heat and smoke release rate during combustion,so as to enhanced the flame retardancy of PBT.FRX-210 decreased tensile strength and flexural strength of PBT,and had the greatest influence on impact strength.Methylphenylpolyborosiloxane(PB)flame retardants were synthesized through two-step synthesis reaction using diphenyldimethoxysilane,dimethyldimethoxysilane,boric acid as the raw materials.When adding 10wt%this polyborosiloxane flame retardant into the PC/PBT alloy,the LOI of the PC/PBT alloy increased from 22.8%to 32.8%.Cone calorimetry analysis showed that PB not only reduced the release rate of heat,smoke,CO and CO2 of PC/PBT alloy,improved fire performance index,but also can help alleviate the combustion process and prevent material from releasing a lot of heat in a short time,which will surely decline the danger during combustion.PB can reach the aim of flame retardancy,through the condensed phase flame retardant mechanism,which reduces mass loss during combustion to promote the formation of carbon residue,and the carbon layer tightly cover the surface of the matrix,thus reduces diffusion of oxygen and thermal radiation.Adding PB could reduce the mechanical property of PC/PBT,especially for notch impact strength.AX8900,maleic anhydride grafted ABS(KT-3),triphenyl phosphate(TPPi)were applied for mechanical property modification of PC/PBT/PB alloy.Moderate amount of TPPi could improve mechanical properties of PC/PBT/PB alloy,but excessive TPPi would cause mechanical performance degradation.TPPi had little impact on vicat softening point of the alloy system.Adding AX8900 alone had almost no improvement of the mechanical properties,while using a combination of AX8900 and TPPi would effectively enhance the mechanical properties of the alloy,especially for impact strength.Adding 3wt%AX8900 and 2%wt TPPi was most effective atthe notched impact strength(up to 4.6 kJ·m-2),increasing 15%compared to PC/PBT alloy without flame retardants.Besides,compatitlizer KT-3 is able to efficaciously improve mechanical properties of PC/PBT/PB alloy.