Preparation And Performance Research Of Oil-resistant Halogen-free Flame Retardant Composites

In the fields of automobiles,rail transit,petroleum exploration,power transportation,etc.,the problems of traditional cable materials in fuel oil,such as easy corrosion,aging,short-circuit leakage and fire-prone,are becoming increasingly prominent,leading to an increasing demand for high-performance oil-resistant halogen-free flame retardant materials.Herein,in this work,the preparation and performance of oil-resistant halogen-free flame retardant composites were studied.The main research work is as follows:Ethylene-vinyl acetate copolymer(EVA)/aluminum hydride(ATH)composites were prepared by melt blending and ultraviolet radiation crosslinking,and the effects of material polarity,crystallinity,compatibility between polymer matrix and inorganic flame retardants,UV crosslinking on the oil resistance of EVA/ATH composites were studied by means of differential scanning calorimeter(DSC),scanning electron microscope(SEM),oil resistance and mechanical property tests.The results show that as the polarity and crystallinity of the material increase,the oil resistance of EVA/ATH composites increases.Moreover,the formation of the polymer crosslinking network also moderately improve the oil resistance of the EVA/ATH composites.Especially,the compatibility between the polymer matrix and the inorganic flame retardants has a greater influence on the oil resistance of the EVA/ATH composites.Maleic anhydride grafted polyethylene(PE-g-MAH)improves the compatibility between EVA and ATH and consequently the oil resistance of the EVA/ATH composites has been significantly improved.A series of EVA/PE-g-MAH flame retardant crosslinked composites were prepared with ATH and piperazine pyrophosphate(PPAP)as flame retardants.Limit oxygen index(LOI),UL-94 vertical combustion,thermogravimetric analysis(TGA),cone calorimetry(CCT),SEM,mechanical property test results show that when the total amount of flame retardant added is 50 wt.%,and the mass ratio of ATH and PPAP is 3:2,EVA/PE-g-MAH/ATH/PPAP composite can reach UL-94 V-0 level,and the LOI value is as high as 27.3%.Replacing ATH with an appropriate amount of PPAP,the heat release rate(HRR)and total heat release amount(THR)of the composite both decrease,while the residual carbon rate of the system and firmness of carbon layer increase significantly.When the materials are immersed in 3 # standard oil at 40 ? for 72 h,the retention rate of tensile strength reaches 70.56%,and theelongation at break increase by 11.76%.Using thermoplastic polyester elastomer(TPEE)as oil-resistant substrate,magnesium hydroxide(MH)and aluminum hypophosphite(AHP)as flame retardants,a series of TPEE flame retardant crosslinked composites were prepared.The non-isothermal crystallization behaviors of TPEE at different cooling rates were studied by DSC.The results show that with the increase of the proportion of polyester hard segments in TPEE,the crystallization temperature of TPEE increases,the crystallization rate becomes faster,and the crystallization ability becomes stronger.The results of LOI,UL-94 vertical combustion,TGA,CCT and mechanical property tests show that the increase of the proportion of polyester hard segment helps to improve the flame retardant performance and oil resistance of the TPEE/MH/AHP composites.When the total addition amount of MH/AHP flame retardant is 50 wt.%,and the AHP content is 5 wt.%,the LOI value of composites with Shore D55 hardness TPEE reaches 29.3%,and the UL-94 vertical combustion test can pass V-0 level.When the composites are immersed in 3 # standard oil at 40 ? for 72 h,the retention rate of tensile strength and elongation at break amounts to 92.56%,90.77%,respectively.