Intumescent Flame Retardants For Polyethylene

Polyethylene(PE) has been widely used in many fields such as cable and wire, electrical and electronics industry, etc. However, its low limiting oxygen index (LOI) value and flammablility can not meet the fire safety requirments in many cases. Therefore, it is very important to find an effective and environmental friendly method to improve the flame retardancy of PE.The conventional flame-retardant systems for PE are mainly based on halogen, phosphorus and inorganic hydroxides. For halogenated flame retardants, there are many negative effects on environment, and for inorganic hydroxides the properties of the resulting flame-retardant PE materials are deteriorated due to their high loading. Recently, intumescent flame retardants (IFRs) have received a considerable attention because they are non-halogen, low toxicity, and low smoke release. The IFRs are designed to swell and form a porous carbonaceous char layers on the surface of materials, which act as a barrier to heat, air and flammable pyrolysis products. LOI and vertical burning methods and SEM were used to estimate the flame retarding efficiency of materials, the effects of each ingredient were studied. Configuration and structure of intumescent char were observed with SEM and the mechanism of anti-dropping was discussed.PA-66 was added into the intumescent flame retardant to flame retardant polyethylene (PE). The results shows that the PA-66 can improve the fire performance polyethylene.In LDPE-IFR-PA-66 system, ethylene vinyl acetate copolymer (EVA-28) was used to improve the compatibility of intumescent flame retardant, PA-66 and LDPE. The influence of EVA-28 content on the mechanical property and flame retardant property of complex material was studied. The reaction conditions were optimized. Based on the results of LOI and UL-94 tests, one formulations with best flame retardancy were obtained:50%LDPE+40%IFR (30%APP+10%PER)+10%PA-66 +50%EVA-28, which LOI was 27 8.Some metal-containing (Fe, Al and Co) complex was used to improve the char formation of the IFR system. The results show that metal-containing complex can convert alkylperoxy radicals to more stable species.A novel silicone flame retardant was synthesized based on phenyl trimethoxysiane, diphenyl dimethoxy silane and boric. It exhibit good flame retardancy and synergism when combined with ammonium polyphosphate (APP)/pentaerythritol (PER)/Nylon-66 and ethylene vinyl acetate in PE substrate.