Study On Halogen-free Intumescent Flame Retardants For A Novel Thermoplastic Elastomer OBC

The novel thermoplastic elastomer OBC has higher melting,crystallization temperature, and excellent abrasion resistance. Besides,OBC can be rapidly prototyping in the process of molding. The elasticrecovery and compression set properties of OBC are remarkable, so it canbe widely used in the pipe, film, foam, automobile parts, footwear andother fields. However, the limiting oxygen index of OBC is low and theflammable of OBC is highly, which limits its application. The flame-retardant technologies of OBC has important implications.The halogen-containing flame retardants that used in the polymermaterial are serious environmental problems and therefore halogenatedflame retardant is banned in many applications. Recently, intumescentflame retardants （IFRs） have received a considerable attention becausethey are non-halogen, low toxicity, and low smoke release. The IFRs aredesigned to swell and form a porous carbonaceous char layers on thesurface of materials, which act as a barrier to heat, air and flammablepyrolysis products.In this paper, intumescent retardant system is composed of melaminephosphate（MP） and pentaerythritol（PER）. Meanwhile, nylon12（PA12）,basic nickel carbonate （NiCO₃2Ni（OH）₂4H₂O）, lanthanum oxide（La₂O₃）, expanded graphite （EG） and its complex with IFR were addedinto the flame retardant system, respectively. The performance andmechanism of each flame-retardant system were evaluated by Limitingoxygen index, vertical flame test, thermal gravimetric analysis, scanningelectron microscopy, infrared spectroscopy, tensile properties testingand rheological measurement, etc.The study showed the effect of flame retardant is significantly enhanced when PA12, NiCO32Ni（OH）₂4H₂O, La₂O₃or EG are addedinto system. The better comprehensive properties of the flame retardantmaterial can be obtained when ration of the each component is proper.The Limiting oxygen index of composites was29.3and UL-94testgot V-0when the concentration of PA12is6.4wt%. The compatibilityperformance of PA12improve the mechanical properties of flame-retardant materials.Even small amount of basic nickel carbonate can significantlyimprove the flame-retardant properties of the OBC/MP/PER composites.The Limiting oxygen index of composites is28.5and UL-94test got V-0when the concentration of basic nickel carbonate is0.5wt%.La₂O₃has good synergistic effect with MP/PER system, so theLimiting oxygen index of composites is30.0and UL-94test got V-0whenthe concentration of La₂O₃is1.5wt%.EG has excellent synergistic effect with MP/PER system. TheLimiting oxygen index of OBC/MP/PER/EG composites is above28.0andUL-94test got V-0when the concentration of EG is between15wt%～18wt%.