Study On The Properties And Flameretardant Mechanism Of Halogen-free Flame Retardant Abs Resin

The flame retardant acrylonitrile-butadiene-styrene materials(FR ABS)containing halogen are restricted in ecological environment due to the fact that they release lots of toxic and corrosive gases while burning.It is very necessary to synthesis and develop the new and efficient halogen-free flame retardant system.In the present paper,for the target of research halogen-free flame retardant ABS resin,silicone resin flame retardant,intumescent flame retardant(IFR),phosphorus-based flame retardant aluminum hypophosphite(Al(H2PO2)3)were selected as flame retardants of ABS resin.Limited oxygen index(LOI),UL 94 testing and CONE calorimeter were used to study flame retardancy property of FR ABS composites.To further enhance flame retardancy efficiency of FR ABS,the synergistic flame retardant systems contain silicone resin and IFR,silicone and Al(H2PO2)3 were also applied in ABS resin;and the synergistic flame retardancy mechanism of the flame-retardant ABS was further investigated through thermogravimetric analysis-Fourier transform Infrared spectroscopy(TG-FTIR),scanning electron microscope(SEM)and energy-dispersive spectroscopy(EDS).The main contents are as the follows:(1)The silicone resin flame retardants with different structure were successfully synthesized through hydrolysis condensation reaction by using phenyl trimethoxy silane,methyl triethoxy silane,and aminopropyl methyl diethoxyl silane as raw materials.The chemical structure of silicone resins were characterized by FT-IR and Nuclear Magnetic Resonance spectroscopy('H-NMR).The thermal performance of silicone resins were characterized by TGA.The results showed that the char yield of the best thermal stability modified amino phenyl silicone was 66.5%at 800? under N2 atmosphere and the initial thermal degradation temperature was 413.9?,which is higher than the processing temperature of ABS,thus the silicone resin could be applied in ABS flame retardant.(2)The effect of different types of silicone resins on flame retardant of ABS was studied,the results showed the addition of the silicone resin in ABS should not exceed 2wt%.The synergistic effect of silicone resin with IFR flame retardant ABS was investigated.The results demonstrated that the LOI of ABS/IFR/NH2-Ph-Si(70/28/2)composite was 29%,which was increased by 61.11%compared with pure ABS.However,the tensile strength,flexural strength and unnotched strength of flame retardant ABS composites decreased sharply.(3)The effect of different content of Al(H2PO2)3 on the flame retardancy and mechanical property of ABS were studied,the results showed that the UL 94 testing level of ABS with 25 wt%Al(H2PO2)3 was V-0.However,Al(H2PO2)3 had negative effect on impact strength of ABS composites.The flame retardant mechanism of ABS/Al(H2PO2)3 composites was investigated by TG-FTIR,CONE testing,the results showed that flame mechanism of the ABS/Al(H2PO2)3 composite is typical condensed phase flame retardant.Aluminum Phosphate produced by thermal decomposition of Al(H2PO2)3 could catalyze the char formation of ABS.The char layers could protect polymer matrix from oxygen and heat,and caused improvement of thermal stability and flame retardancy of ABS.It could be observed through SEM that the char layers accumulated densely and the char surface distributed with random pores,which extended the propagation path of heat and oxygen and deceased propagation efficiency.The peak heat release rate and smoke generation rate of ABS/Al(H2PO2)3 composite were decreased.(4)In order to improve the flame retardant efficiency of ABS/Al(H2PO2)3 composite,two kinds of synergistic agents,NH2-Ph-Si and melamine cyanurate(MCA)were used separately with ABS/Al(H2PO2)3 flame retardant system.The LOI of ABS/Al(H2PO2)3/NH2-Ph-Si(78/20/2)composite was 26.5%,UL 94 testing was V-0;the synergistic effect between P and Si was more obvious.TG-FTIR,CONE and EDS tests results showed that Al(H2PO2)3/NH2-Ph-Si synergistic flame retardant system played flame retardant in the agglomeration phase,Si from NH2-Ph-Si would migrate toward the surface during combustion,P and Si can be helpful to form a firm char of high thermal stability,the char could effectively improve flame retardant properties of the ABS.The LOI of ABS/Al(H2PO2)3/MCA(78/20/2)is 26%,and the UL 94 testing level was V-0.NH3 and NO2 released by thermal decomposition of MCA could form a gas barrier layer;meanwhile NH3 could catalyze the esterification reaction between ABS and Al(H2PO2)3.The char protected ABS matrix from heat and oxygen,further reduced the degradation rate of ABS composites.