联枯/次磷酸铝/MHB对聚丙烯的阻燃机理

Flame Retardant Mechanism of Bicummyl/Aluminium Hypophosphite/Melamine Hydrobromide in Polypropylene

通过熔体流动速率测定、热重分析、锥形量热试验的残余物分析和热裂解气相色谱质谱联用分析,探讨了联枯/次磷酸铝(ALHP)/三聚氰胺氢溴酸盐(MHB)对聚丙烯(PP)的阻燃机理。结果表明:联枯裂解产生的二甲基苯基叔碳自由基、ALHP裂解产生的磷烷(H3P)和MHB裂解产生的溴化氢(HBr),协同捕获燃烧过程中的活性自由基(如·OH),终止燃烧反应链而抑制燃烧,进而产生良好的气相阻燃作用;ALHP裂解和氧化产生的聚偏磷酸和HBr等酸性物质使PP脱水和炭化,因而减少了可燃挥发性裂解产物的形成,并且生成的炭覆盖在基材表面,从而起到凝聚相阻燃作用;MHB裂解产生的N2,NH3,CO2等惰性气体对燃烧区的氧产生稀释作用而导致阻燃。联枯促进了MHB的裂解从而改善了阻燃作用。

The flame retardant mechanism of bicummyl/aluminium hypophosphite/melamine hydrobromide in polypropylene(PP)was studied by the measurement of melt flow rate,thermogravimetric analysis,analysis of the residues obtained in cone calorimeter test and pyrolysis-gas chromatography/mass spectrometry.The results show that dimethylphenyltertcarbon radical produced by the cracking of bicummyl,together with H3P and HBr produced respectively by the cracking of ALHP and MHB,capture the active radicals(such as·OH)in the combustion process,so that the chain reaction of combustion is interrupted,which results in an efficient flame retardancy in gaseous phase.Acidic compounds such as polymetaphosphoric acid produced by cracking and oxydation of ALHP and HBr make PP dehydration and carbonization,so as to reduce combustible volatile cracking products,and the formed carbon covers the surface of substrate to play a role of condensed phase flame retardant.N2,NH3,CO2 and other inert gases produced by MHB cracking dilute the oxygen in the gaseous combustion area,which results in flame retardancy.Bicummyl promotes the cracking of MHB,and improves the flame retardancy.