Preparation And Properties Of PO/EVA-g-MAH/IFR Flame Retardant Cable Compound

With the rapid development of science and technology,the demand forspecial purpose flame retardant wire and cable is increasing,and its performance requirements are also more stringent.The flame retardancy and oil resistance of special special cables such as locomotive cables,oil well cables,charging pile cables and automotive cables have become the hotspots of research.The domestic special flame retardant cable materials or base resins with good oil resistance are mostly imported,and the problems of high price and long delivery time seriously restrict the development of the industry.How to improve the oil resistance of the resin is the key to solving the problem.At present,polyolefin（PO）materials widely used have the advantages of good electrical properties,excellent mechanics,and good processing properties,but the flame retardancy and oil resistance are poor,and the requirements of the above special special flame retardant cables cannot be met.Therefore,in this paper,maleic anhydride（MAH）was grafted onto the EVA molecular chain,and polar groups were introduced to further improve the oil resistance of PO.The oil resistance of EVA-g-MAH to low-smoke halogen-free flame retardant polyolefin cable materials was studied.The mechanical properties,electrical properties and other effects lay a solid foundation for the preparation of high-oil-resistant flame retardant cable materials.In this paper,EVA was grafted by melt grafting method,and diisopropylbenzene（DCP）was used as initiator,MAH was used as grafting monomer,and styrene（St）was used as side reaction inhibitor to prepare EVA grafted product.The grafting rate and melt index method were used to characterize the degree of graft side reaction by chemical titration.The effects of DCP,St,MAH,reaction temperature,time and rotation speed on the grafting rate were studied to determine the optimum process parameters.The results showed that the grafting rate increased first and then decreased with the increase of DCP dosage.The excessive use of DCP increased the side reaction.The introduction of St significantly increased the grafting ratio of MAH,and effectively inhibited the graft side reaction.Compared with the grafting rate,the maximum increase can be 61.1%;Excessive amount of MAH will cause the homopolymerization reaction between MAH,which will cause the grafting rate to decrease.With the increase of reaction temperature,the increase of rotation speed and the prolongation of time,the grafting rate will increase first and then decrease.When the material weight ratio was EVA:MAH:St:DCP=100:4:4:0.35,the reaction temperature was 170°C,the rotation speed was 50 r/min,and the grafting rate was up to 0.87%at 9 min.Characterization of the infrared spectrum confirmed that MAH had been grafted onto the EVA molecular chain.Inthispaper,ammoniumpolyphosphate（APP-OS）and1,3,5-trishydroxyethyl isocyanurate（THEIC）were selected to form an intumescent flame retardant system（IFR）to optimize the ratio of IFR;explore the PO/IFR system.Flame retardant properties.The results showed that when the weight ratio was:APP-OS:THEIC=3:2,PO:IFR=15:7,the material system had the best flame retardant effect,the oxygen index reaches the maximum value of 30.5%,and the vertical combustion energy passes through V-0.level.The paper also studied the PO/EVA-g-MAH/IFR intumescent flame retardant system,and mainly studied the effect of self-made EVA-g-MAH on the comprehensive performance of the intumescent flame retardant system.The results showd that with the increase of EVA-g-MAH,the compatibility of composites was further improved,the oil resistance was significantly improved,the elongation at break was continuously increased,and the tensile strength was first increased and then decreased,and the oxygen index was increased.The breakdown field strength increases,but had little effect on the volume resistivity.When the amount of EVA-g-MAH added was 8 wt%,the composite material had the best overall performance.The oil-resistant test tensile strength change rate was-39.1%,and the oil resistance test elongation at break was+48.8%,which was 38.1%,65.6%,tensile strength 15.8 MPa,and elongation at break,respectively,compared with the composite without added graft.The long rate was 278%,the volume resistivity was 1.25×10¹³Ω·m,the breakdown strength was 23.5 MV·m^-1,the oxygen index was 32.3%,and the vertical combustion passed through the V-0 level.