Surface Modification Of Magnesium Hydroxide And Its Flame Retardant Application In Vinyl Acetate Copolymer

The inorganic flame retardant magnesium hydroxide(MH)had become one of the most commonly used flame retardants for ethylene-vinyl acetate(EVA)composites due to its low cost,environmental protection and excellent smoke suppression effect.However,the larger surface polarity and higher amount of MH often affected the processability and mechanical properties of EVA composites.In this work,a flame-retardant EVA composite with excellent comprehensive performance was prepared by improving the surface polarity of MH.The specific research contents were as follows:1.Red phosphorus(RP),zinc borate(ZnB)and MH were added to the EVA material by melt blending,and EVA/(2%ZnB+48%MH)and EVA/(5%RP+45%MH)composites were prepared respectively.Through the flame retardant performance evaluation,when the best mass ratio between ZnB and MH was 24:1,and the best mass ratio between RP and MH was 9:1,the composites exhibited the best flame retardant properties.In addition,analyzing and comparing the combustion behavior of the two composites,the synergistic flame retardant effect of RP was better than that of ZnB,and the combination with MH could play a better flame retardant synergistic effect.2.The surface coating treatment of MH was carried out by using organosilicon oligomer CCSi to obtain CCSi@MH,and the EVA/(5%RP+45%CCSi@MH)composites were prepared by compounding with RP.The vertical combustion(UL-94)of the sample reached the V-0 rating,and the limiting oxygen index(LOI)was increased from 24%to 31%compared with control EVA.The tensile strength of EVA/(5%RP+45%CCSi@MH)composites increased from 2.7 MPa to 3.7 MPa and the elongation at break increased from 37.0%to 52.3%compared to EVA/(5%RP+45%MH)composites.And the corresponding storage modulus in the dynamic mechanical test increased from 1189 MPa to 1335 MPa.Due to the surface coating treatment of MH by CCSi,the dispersibility of MH in EVA was improved,and had the lubricating effect in dynamic stretching.3.The organometallic framework ZIF8 was used for surface growth on MH to obtain ZIF8-MH.The EVA/(5%RP+45%ZIF8-MH)composites was obtained by compounding with RP and EVA material,and LOI was increased to 34%,reaching V-0 rating of the UL-94 test.The effective combustion heat of EVA/(5%RP+45%ZIF8-MH)composites decreased to 17.4 MJ/kg,and the total smoke production decreased to 8.1 m2.The reason was that ZIF8 promoted the formation of carbon by metallic zinc to form denser char and its unique cavity structure played the good role in gases adsorption.