Study On Processing Conditions Of Halogen-free Flame-retardant Polyolefin Foam Material

Polyolefin foam material has been used widely because of its many advantagessuch as the light weight, low thermal conductivity, low moisture-penetrability andlow cost, etc. But as a kind of macromolecule material, it is easy to cause a fire in afire source. Flame retardant often were added to polyolefin foam material to improveits flame retardancy. However, halogen flame retardant adopted by most willproduce secondary harm to the environment in the fire. Therefore, the developmentof the halogen-free flame-retardant polyolefin foam material gradually becomes theresearch hotpot recently. This thesis will determine the best ratio of flame-retardants,process methods and conditions through the research in the influence of halogen-freeflame retardant association agent on flame retardancy and mechanical properties offlame retardant foam material, in addition, its flame-retardant mechanism wasanalyzed.In this paper, the three kinds of surface modifiers (titanate, stearic acid and silanecoupling agent KH-550) were used to modify the magnesium hydroxide(MH),though dry method. The influence of surface modifier and content on the flameretardancy and mechanical properties of flame-retardant foam was studied. Theexperimental results showed that silane coupling agent has the best modificationeffect. Some comparative study were done after the two types ofMg(OH)2(nano-meter Mg(OH)2and micro-meter Mg(OH)2)were filled inflame-retardant foam, nano-meter Mg(OH)2is superior to micro-meter Mg(OH)2.The weaknesses of magnesium hydroxide, such as low flame-retardant effect,large filling, have large effect on the mechanical properties, etc. Therefore, redphosphorus, MCA, and organic silicon were chosen to act as flame retardant withMg(OH)2together. The Study of effects of flame-retardant synergist on the flameretardancy and mechanical properties of flame-retardant foam was carried inMg(OH)260phr to main material100phr..The results showed that the red phosphorushad an important influence on flame-retardant foam, both MCA and organic silicon flame retardant also improved mechanical properties. An optimum formula that hadgood flame-retarded properties was got with Mg(OH)260phr, red phosphorus6phr,organic silicon6phr, MCA15phr by orthogonal experiment. The tensile strength offlame-retardant foam is1.14MPa, the dimension on the elongation is198%, the LOIcan reach to31.5%, and the vertical burning come up to FV-1.The effects of flame-retardant on processing conditions of foam was studied. Theresults showed that the viscosity of flame-retardant foam was significantly improved.The best molding temperature has been enhance from175℃to185℃, the bestmolding time has been extend from330s to360s. Then the tensile strength offlame-retardant foam is1.23MPa, the dimension on the elongation is215%, the LOIcan reach to32.1%, exerting a good flame retardancy and mechanical propertieslevel.Finally, study the flame-retardant mechanism of the polyolefin system which hasbeen primarily investigated. The results showed that the red phosphorus turn intophosphoric acid and phosphorate by combustion. It can accelerate the decompositionof magnesium hydroxide and promote to increase the residual carbon amount.Silicone turns into isolated layer similar to SiC. The MCA produces the inert gas todilute the oxygen density. Ultimately, Statistics indicate that the accession ofmagnesium hydroxide, red phosphorus, MCA and organic silicon have reduced theinitial degradation temperature of combustion foam system and improve the residualcarbon amount by TG and DTA methods.