Preparation And Properties Of Intumescent Flame Retardant Low-density Polyethylene

Low-density polyethylene(LDPE)has excellent performance and wide application,but it is extremely flammable and releases a large amount of heat after combustion,which severely limits the application range of LDPE.Therefore,in order to improve the fire safety in practical application,LDPE is adopted flame retardant procession is required.On the basis of fully analyzing the flame retardant technology for LDPE,novel flame retardant LDPE composites are prepared based on two kinds of intumescent flame retardant systems in this paper.The main research work of this paper is as follows:1.Flame retardant LDPE composites are prepared based on microencapsulated ammonium polyphosphate(MCAPP)and tris(2-hydroxyethyl)isocyanurate(THEIC).The results show that the optimal ratio of MCAPP to THEIC is 2:1 when the total addition amount of flame retardants is 30%,and LDPE/MCAPP/THEIC has a LOI of up to 33.2% and can pass the UL-94 V-0 rating.LDPE/MCAPP/THEIC has better thermal stability and higher char residue than pure LDPE at high temperature,the char residue of LDPE/MCAPP/THEIC at 450oC reaches up to 65.4%,which is far higher than that of pure LDPE(7.7%).LDPE/MCAPP/THEIC has the best tensile mechanical properties when MCAPP/THEIC is 2:1.MCAPP and THEIC have good synergistic effect on flame retardancy,and the combination of them can effectively reduce the heat release rate and total heat release of LDPE composites.The peak heat release rate and total heat release are reduced by 74.8% and 66.9%,respectively,compared to those of pure LDPE.The quantitative judgment of fire performance index and fire growth index proves that LDPE/MCAPP/THEIC have better fire safety.It is found that the intumescent char layer formed by LDPE/MCAPP/THEIC can be dense,homogeneous and strong under the optimum MCAPP/THEIC addition ratio,and the silicon element in the shell materials of MCAPP increases the strength and stability of the char layer,which can effectively reduce the spread of flammable gases and heat,thereby improving the flame retardancy and thermal stability of LDPE.2.On the basis of the first part,the double-layer microencapsulated ammonium polyphosphate(C=C-MCAPP)containing vinyl functional groups in the shell materials is prepared by the continuous gel-sol method at different temperatures.Flame retardant LDPE composites are prepared by blending C=C-MCAPP and THEIC at the optimum ratio of 2:1.The contact angle and water solubility tests of APP show that the water contact angle of C=C-MCAPP increases by 68.9% and the solubility decreases by 74.7% compared with MCAPP,which indicates that the hydrophobicity and water resistance of APP are greatly improved after vinyl functionalization modification.The LOI of LDPE/C=C-MCAPP/THEIC is slightly higher than that of LDPE/MCAPP/THEIC,indicating that C=C-MCAPP has a certain effect on improving the flame retardany of LDPE composites.In addition,the study on mechanical properties shows that C=C-MCAPP can improve the ductility of flame retardant LDPE composites in comparison of MCAPP.Figure [30] Table [13] Reference [80]...