Preparation Of Low Smoke And Halogen-Free Flame Retardant Oil Resistant Composites

Ethylene-vinyl acetate copolymer (EVA) is plastic with good mechanical properties, dyeing property and machinability, and nitrile butadiene rubber (NBR) is one of the best oil resistant special rubbers. In this work, EVA and NBR were blended together to obtain oil resistance material and the mechanical properties, flame retardancy and thermal stability were studied.In this work, silane coupling agent Si69was used to modify magnesium hydroxide (MH) to improve the surface activity and lipophilicity of MH. Then, halogen free flame retardant and oil resistant blends were prepared by blending EVA/NBR with a flame retardant system which contains modified MH and red phosphorus. Micro control universal testing machine, limit oxygen index apparatus, vertical burning test instrument, cone calorimeter, smoke density box and thermogravimetric analyzer were used to analyze effect of attapulgite, zinc methacrylate and nano-SiO2on the EVA/NBR blends. The results showed that the addition of attapulgite had improved the tensile strength, oil resistance and flame retardant of the blends, but effects were not so significant. Zinc methacrylate was perfectly improved the tensile properties and oil resistance of the blends, the tensile strength could reach15.6MPa and the elongation at break could also reach525.1%with the loading of40phr zinc methacrylate. When the material was immersed in the40℃20#engine oil for72h and75℃20#engine oil for48h, the reduced rate of tensile strength was only74%,39.2%respectively, showed prominent properties. Nano-SiOi was good for improving the overall performance such as tensile strength, oil resistance, flame retardancy, thermal stability and especially smoke suppression. The maximum smoke density value (MSD) of the blend with40phr nano-SiO2was reduced from93.7to81.8and the smoke density rate (SDR) reduced from63.7to53.1, smoke released was suppressed and further add0.5phr molybdenum trioxide to the EVA/NBR/nano-SiO2blend, the MSD and SDR of the system reduced to60.7and43.3respectively, showed outstanding smoke suppression property. At the same time, the effects of molybdenum trioxide on the tensile properties and oil resistance were very small, but flame retardancy of the blend improved significantly, the limited oxygen index (LOI) could reach33.2, vertical flame rating could reach V-0and the peak heat release rate (PHRR) was only241kW/m2.