Preparation And Study Properties Of EVA Conductivity Flame Retardant Composites

Ethylene-vinyl acetate copolymer(EVA)with mechanical and physical properties,its were varied applied in many fields, such as electrical and electronic parts,packaging materials, medical appliance, flame retardant wire and cable industry,semiconductor shield materials, etc. However, EVA has low limiting oxygen index(LOI) value of18.5and is flammable，which is easy to bring about fire; on the otherhand, EVA is inherently an electrical insulator, exhibiting the surface resistivity of1016~1020, the static charge that easily builds up on such molded parts by contact orrubbing may cause an elelctrostatic discharge, which becomes a serious problem. Forthese reasons, which restrict their practical applications. Therefore, the flame retardantand conductivity modification of EVA is being attached importance to more and morein industry.In this paper, formulation of flame retardant and conductivity EVA compositeswere designed; effects of additives and process on flame retardant and conductivityproperties of EVA composites were investigated.In this work, a variety of flame retardants and conductive carbon black and otheradditives have been blended with EVA in internal mixer, the machine can mix samplehomogeneously, and then, the blend to be vulcanized on the plate vulcanizingmachine. Finally, characterization was carried out based on the experimentalrequirements and properties of treated composites were investigated. Seriesconductivity and flame retardant composites were prepared by means of blendingEVA with three kinds of flame retardance and three trademarks of conductive carbonblack. Three kinds of flame retardant additions:(1) Magnesium hydroxide (MH)/expanded graphite(EG)/polygorskite(PGS) flame retardance system;(2) Redphosphorus(RP)/expanded graphite(EG)/polygorskite(PGS) flame retardance system;(3) Ammonium polyphosphate/expanded graphite(EG)/polygorskite(PGS) flameretardance system; Three trademarks of conductive carbon black: F-900, T-80andVXC-72R.Flame-retardant properties, mechanical properties, volume resistivity, heatresistance and the dispersion of flame retardant and carbon black in EVA have beeninvestigated by limiting oxygen index instrument (LOI), the Vertical burning test, universal tensile testing machine, semiconductor of rubber and plastic testing machine,TG-DTA and scanning electronic mirror (SEM) respectively. The results show thatthe total amount of PGS/MH/EG flame retardant is25phr andthe total amount ofconductive carbon black is25phr, the volume resistivity can reach10.0·cm around,and the tensile strength investigation indicated that the materials has better physicaland mechanical properties by surface modification, the mechanical properties reach tothe maximum, tensile strength more than10.0Mpa, Elongation ratio more than600.00%.The composites to meet the flame retardant wire and cable, power cablesemiconductor shield materials, antistatic of packing film and cage, electromagneticshielding materials, it has a good appliance prospect.