Study On Combustion Behavior And Mechanical Properties Of Intumescent Flame Retardant Synergistic With Magnesium/Aluminum Hydroxide Flame Retardant Polyolefin Composite

Polyethylene(PE)and ethylene vinyl acetate(EVA),as a common plastic,have been widely used in many fields of daily life and industrial production,such as agricultural film,wire and cable,communication,building and aerospace manufacturing,because of their excellent processing and mechanical properties.But their main elements are C,H making them flammable,and it has the risk of fire.This severely limits its application.In order to overcome the flammability of materials,the addition of flame retardants is expected to improve the flame retardancy of materials.In this paper,linear low density polyethylene(LLDPE)and high density polyethylene(HDPE)are used as matrix,magnesium hydroxide(MH)and aluminum hydroxide(ATH)are used as the main flame retardants.Zinc borate(ZB)and the organic modified expansible graphite(MEG)are used as synergistic agents,EVA is used as the compatibilizer between the matrix and the fillers.In order to strengthen the compatibility between the fillers and the matrix,we use the silane coupling agent(KH-560)to modify MH and ATH.The structure of the modified MH is measured and characterized by Fourier infrared spectroscopy(FTIR)and scanning electron microscopy(SEM).MEG is obtained by grafting the phosphorous flame retardant(DOPO)and KH-560 to the expansible graphite(EG).In this paper,LLDPE/EVA/MH/ATH composites are prepared by melt blending.The effects of MH and ATH content,the synergistic effects of MEG,and the synergistic MEG,ZB with MH/ATH on the flame retardancy,thermal stability,combustion behaviors and mechanical properties of LLDPE/EVA and HDPE/EVA composites are investigated.The main conclusions of this work are as follows:1.After the modification of MH and ATH,the characteristic peaks of KH-560 appear in the FTIR spectra and the result of SEM shows that the dispersion of modified MH is improved.The effects of MH and ATH on the structure and properties of LLDPE/EVA composites are studied.The UL-94 results indicate that the content of MH and ATH is 60%,the LE/ATH120 and LE/MH120 samples reach V-0 level,and the LOI values are 32.1 and32.4%,respectively.The conical calorimeter test(CCT)shows that MH and ATH reduce the heat release rate and gas release rate of the flame retardant materials.Because the addition of inorganic filler greatly deteriorates the mechanical properties of the materials,especially the breaking elongation and fracture strength of the flame retardant materials with the addition of 60%are reduced to 18.6%and 9.1 MPa.2.The effects of MEG and MH/ATH on the flame retardancy,combustion behavior,thermal stability and crystallinity of LLDPE/EVA composites were studied.When 10 phr MH/ATH is replaced by MEG,the LOI value of LMEG10 increases to 32.5%,and the V-0level is reached.The heat release rate,the total heat release and the release of gas are reduced,the thermal stability of the composite enhance,and the final carbon residue increases to 38.2%.Because of the reason of heterogeneous nucleation,the addition of MEG increases the crystallinity of flame retardants,but when the MEG content continues to increase,the crystallinity of flame retardants decreases.3.The effect of the combination of ZB and MEG on the properties of LLDPE/EVA/MH-ATH flame retardant materials.When the ratio of ZB and MEG is 2:8,the composite material reaches V-0 level,the LOI value is 31.7%.The heat release rate,the total heat release amount and the release amount of gas are weakened.The carbon layer of the flame retardant material is more complete and compact,and the final carbon residue increases to 37.2%,which improves the flame retardant and thermal stability of the composites.However,because of the addition of MEG,the mechanical properties of composites greatly deteriorate.4.The effects of ZB and MEG on the properties of HDPE/EVA/MH-ATH flame retardants were studied.The compound ratio is 2:8,the LOI value of the flame-retardant materials increases to 37.1%,the vertical combustion reaches V-0 level,and the CCT test of the flame-retardant materials indicates that the PHRR value of the flame-retardant composite has decreased from 458.3 kW/m~2 to 210.3 kW/m~2.The results of TGA show that the thermal stability of the flame-retardant materials is enhanced at high temperature,and the final carbon residue reaches to 33.9%.The results of FTIR test show that phosphoric acid esters can be produced at high temperature to make the material form carbon and strengthen the flame retardancy.In summary,MH,ATH,ZB and MEG are used to flame retardant LLDPE/EVA and HDPE/EVA polymers,which can effectively dilute and reduce the amount of heat and gas released during the combustion of materials.The flame retardancy and thermal stability of the composites are greatly improved.However,it is not difficult to find that the mechanical properties of the composites have been deteriorated to a certain extent after firing retardancy,which needs further research to expand its application field.