Research On Preparation And Properties Of Intumescent Flame Retarded LLDPE/EVA Material

Polyethylene(PE),because of its excellent mechanical properties,electric-insulation, chemistry durability,and easy processing,has been widely applied in many areas.However, PE is easy to catch fire and its limiting oxygen index(LOI)value is only 17%.Therefore people pay more and more attention to improve its flame retardancy.There are three types of flame retardants that are used to improve the flame retardancy of PE,including halogenated flame retardants,metal hydroxides and intumescent flame retardant.Recently,there has been a trend to avoid the use of halogenated flame retardants because of environmental and safety concerns.Metal hydroxides don't pollute the environment.However,a higher loading of metal hydroxides additives(over 50%)is needed than that of some halogen-containing flame retardants.This results in lower mechanical properties of the flame-retardant materials. Intumescent flame retardant,with characters of non-halogen,lower poison and releasing little smoke,has become a hot point in flame retardant area.In this work,a novel intumescent flame retardant(IFR)consisting of CFA,APP and other additives was used to improve the flame retardancy of LLDPE/EVA.Firstly,the flame retardancy and mechanism properties of LLDPE-IFR and EVA-IFR were studied,respectively. Furthermore,the mass rate of LLDPE/EVA in blends was discussed.The result showed that the general properties of material were best when the mass rate of LLDPE/EVA was 78/22.Several factors of flame retardancy of LLDPE/EVA material were also studied,such as the mass rate of APP/CFA,sorts and loading of synergistic agents in IFR.The results showed that the efficiency of IFR was best when APP/CFA was 3/1.Na-MMT,modified-MMT and 4A-zeolite all had a good synergistic effect.While,the synergistic effect of OMMT was best.The material could pass UL-94 V0 rating and LOI value arrived 34.5%when the loading of IFR (OMMT)was 25%.It was different for the most suitable loading of these synergistic agents in IFR such as 8%for OMMT and 7%for 4A zeolite.The thermal degradation behavior and the combustion behavior of flame retardant LLDPE/EVA composites were characterized by thermogravimetric analysis(TGA)and cone calorimeter(CONE),while the morphological structures of char layer was observed by scanning electronic microscopy(SEM).The results showed that the fire danger of LLDPE/EVA material decreased with the addition of IFR.All these IFRs could decrease the heat release rate,the smoke production release rate,total heat release and the time to ignition of flame retardant LLDPE/EVA composites.The synergistic agents could promote the thermal degradation of flame retardant LLDPE/EVA composites,increase the rate of residue carbon. They were helpful to formation of stable and dense char layer that increased the flame retardancy of LLDPE/EVA.