The Research On Preparation And Performance Of Halogen-Free Flame-Retardant Elastomer Composites And Study On The Flame-Retardant Mechanism

In this paper, the laws of various ingredients' influences in halogen-free flame-retardant materials were revealed by studying the new concept intumescent flame-retardant system named after Casico and preparing ethylene-propylene-diene copolymer (EPDM) modified by hydroxides and chemical intumescent flame retardant (IFR) in order to offer help for future research.The burning behaviors of EPDM modified by hydroxides were analyzed by the advanced evaluation method of cone calorimeter. The effects of different additives such as modified hydroxides, synergistic flame retardants (red phosphorus and zinc borate) and plasticizing agent of paraffin oil were minutely discussed. The morphologies of combustion products were also analyzed to reveal their roles of the additives in the combustion process of EPDM. The results showed that the flame-retardant properties of EPDM would be greatly improved when it was filled with a large amount of hydroxides. The flammability parameters also indicated that the red phosphorus and zinc borate might promote the flame resistant performance, but both lead to more smoke; the carbon black was helpful in promoting the flame-retardant properties of EPDM while paraffin oil was harmful evidently. On the mechanical properties, a proper amount of carbon black could be significantly effective. A large amount the hydroxide is harmful owing to the weak interface interaction between it and EPDM matrix, the paraffin oil wasn't so adverse when it was up to 40 phr. High performance strip could prepared by this by this method, which may achieve the comprehensive properties of 8MP on tensile strength,75±3 on hardness (shore A),32% on LOI and 9A on ASTM D2230 B.In this paper, EPDM modified by IFR (NP430) was studied. The effects of elastomer matrix including extra-added acid source and carbon source such were analyzed. The effects of NP430, as well as the ingredients such as paraffin oil, carbon black, calcium carbonate, silicon dioxide, expandable graphite (EG), zinc dimethacrylate (ZDMA) and phenol resin (PF) on the flammability properties of EPDM were evaluated. The flame retardance mechanism of IFR on rubber was also discussed. The results showed that NP430 exhibited excellent flame resistance to EPDM, and extra-added acid source ethylene vinyl acetate (EVA) and carbon source high styrene resin (HS) could further improve its effect. When the mass ratio of EPDM/EVA/HS was 80/8.6/11.4 and the amount of NP430 was 90 phr, the limited oxygen index (LOI) reached 47.6%. The addition of paraffin oil was evidently harmful to the flame-resistance but little effect on the intumescence during burning. The composite could intumesce well with a small amount of organic particles such as ZDMA and PF. It was also found that the normal intumescence was obviously restrained by adding the inorganic fillers such as carbon black, calcium carbonate, silicon dioxide and expandable graphite, since the gases ran out during combustion. As a result, the role of IFR was greatly weakened.This paper studied the new concept flame-retardant system of Casico which was made up of ethylene-acrylate copolymer, silicone elastomer and chalk. Heat treatment under different conditions has also been performed to obtain insight into the flame retardant mechanism. The combustion products were investigated. The results indicate that the flame retardant mechanism of Casico was complex and was related to a number of reactions, e.g. ester pyrolysis of acrylate groups, formation of ionomer by reaction between carboxylic acid and chalk and formation of an intumescent structure stabilized by a protecting char. The addition of inorganic materials such as silica resulted in cracks in the surface of combustion residue, which is harmful to flame retardancy, but the addition of aluminium hydroxides (ATH) could strengthen the the flame retardancy of Casico system as a absorption of heat. The effect of crosslinking with peroxide DCP was not significant. When the mass ratio of EBA/MVQ/CaCO3 was 50/20/30, the mass ratio of residual was 27.2% at 850℃,which is much larger than the mass ratio of CaO theoretically at the level of 16.8%. Then the flame-retardant system of Casico obtained an excellent flame retardancy, the LOI of that was as high as 32.5%.