Preparation And Flame Retardant Properties Of Ammonium Polyphosphate/expandable Graphite/epoxy Resin Matrix Composites

Epoxy resin is widely used in electrical and electronic industry,public transportation,aerospace industry and other fields,but due to its easy combustion,there are some safety hazards in use.Therefore,improving the flame retardant properties of materials and reducing fire hazards have become the concerns of researchers.Ammonium polyphosphate（APP）and expandable graphite（EG）can effectively improve the flame retardant properties of the material,and the processing technology is simple and flexible,and the cost is low.Three flame retardants compounded by APP,EG,APP and EG were added to the epoxy resin to improve the flame retardant properties of the resin.As a bio-based flame retardant resin,daidzein-based epoxy resin（DGED）has excellent mechanical properties and thermal properties.Blending it with epoxy resin E51 can effectively improve the comprehensive properties of epoxy resin.In this paper,the above three flame retardants were added to E51 and E51/DGED to prepare epoxy resin composites with flame retardant properties.The thermal properties of materials are studied by DSC and TGA,the flame retardant properties of resins are studied by limiting oxygen index test（LOI）,horizontal and vertical combustion test（UL-94）,micro-calorimetry test（MCC）,and the flame retardant properties of resin are studied by universal tensile testing machine and impact test The mechanical properties of the resin were studied by the testing machine,and finally the carbon residue and fracture surface morphology of the material were studied by SEM.APP,EG,APP/EG three flame retardants can effectively improve the flame retardant performance and high temperature thermal stability of epoxy resin,but the resin added with APP causes the initial thermal decomposition temperature(T₅ and T₁₀ values)due to the decomposition of APP.has declined.The addition of flame retardant reduces the tensile properties of the material,and the bending properties and impact strength tend to increase first and then decrease.The flame retardant effect of APP/EG is better than that of single component.The LOI value of the E51/APP/EG-10 wt%material was 33.2%,reaching the V-0 level,the carbon residue rate（Y_c,800℃）increased to 27.1%,and the tensile strength and elongation at break of the material decreased to 39.7 MPa and 1.7%;while the flexural strength and flexural strength reached the maximum when the APP/EG addition amount was 5wt%,which increased by 17.3%compared with pure E51.The addition of DGED not only improves the flame retardant properties of the resin,but also increases the glass transition temperature（T_g）of the resin and improves the mechanical properties.When the addition of DGED reaches 30%,the LOI value of the material is 30.5%and reaches the V-1 level,the Y_c increases to 22.3%,but the T₅ and T₁₀ values decrease.The daidzein-based epoxy resin composites have better flame retardancy,thermal stability and mechanical properties than pure E51 system.When 2.5 wt%APP/EG was added,the LOI value of the material reached 29.5%and V-0 level.The bending strength and impact strength reached 152.8 MPa and 25.6k J/m²,which were 48.9%and 143%higher than that of pure E51,respectively.