Study On Preparation And Properties Of A Ceramifizable EVA Flame Retardant Material

Ethylene-vinyl acetate copolymer?EVA?is widely used due to its excellent flexibility,adhesion,impact resistance,heat sealability and filler compatibility,but the flammability of EVA makes it difficult to expand its scope of application.Generally,the method of adding flame retardant is used to improve the flame retardant performance.Although the flame retardant is added to delay the combustion,under the condition of continuous fire supply,the EVA flame retardant material will be ablated into carbon residue,losing the structural strength,and cannot guarantee the operation of protected facilities.Introduce some additives or silane compounds containing silicon in the segment.At normal temperature,the polymer material is similar to the general polymer,and at high temperature,it turns into a ceramic-like body with hard characteristics and certain fire resistance.So called ceramifying composite materials.In this thesis,the effects of ceramic-forming fillers,fluxes,and flame retardants on the ceramic-forming properties,flame retardant properties,and mechanical properties of ceramicized EVA flame retardant materials are mainly studied to determine the optimal blending ratio,process methods,and conditions.Firstly,the effects of three processing aids white carbon black,paraffin and polyethylene glycol on the mechanical properties of EVA substrate were investigated through single factor and orthogonal experiments.The research showed that the added amounts were 25 phr of white carbon and 5 phr of paraffin.When the polyethylene glycol is 6 phr,the mechanical properties of the EVA substrate are the best.The proper mixing ratio and amount of wollastonite/talc ceramification components system were studied.When the wollastonite/ talc ratio was 3:2,the mechanical properties of the material were better.Increasing the content of ceramification components can improve the ablation performance of the composite material.When the addition amount is 60 phr,the mass ablation rate is 0.00356 g/s at 1000?,compared with 20 phr,the reduction is 53.98%.However,the addition of filler reduces the mechanical properties of the composite material system,The ablation residue maintains the shape before the ablation,but the bending strength of the ablation residue is low,and the phenomenon of collapse will occur under the action of a small force.In order to improve the porcelain-forming properties and flame retardancy of ceramifying flame retardant materials,the effects of three different fluxing agent on the ablation rate,dimensional deformation rate,and strength of ablation residues were compared.UL-94 combustion level test and limit were used.The limiting oxygen index characterizes flame retardancy.Among them,when the amount of fluxing agent A is 50 phr,it has the best effect on improving the ceramic performance of composites.The mass ablation rate was reduced to 0.00162 g/s,and the bending strength of the ablation residue was 2.49 MPa.The flame retardant melamine polyphosphate/aluminum hypophosphite?MPP/AHP?compounding ratio is 1:1,when the amount is 50 phr,the flame retardant level reaches V-0 level,and the limiting oxygen index reaches 30.7% of the flame retardant The flame retardant has a slight influence on the ceramization performance of the composite material,and the mass ablation rate is 0.00150 g/s.The gas released by the flame retardant at high temperature maintains the deformation of the material.At 1000?,the dimensional deformation rate is less than 10%.The analysis of the infrared,TG and DTG data from the combustion of residual carbon shows that the addition of flame retardants has increased the amount of carbon formed in the system and the initial decomposition temperature,and a more obvious phenomenon of carbon formation has occurred.The formation of the carbon layer acts as a barrier against oxygen.The function prevents the contact between the inside of the composite material and the outside oxygen,provides a foundation for the formation of the ceramic layer,and can also partly participate in the reaction of generating the ceramic composite material.The flame retardant itself releases gases that,while diluting oxygen,also serve the purpose of maintaining the shape of the material.Compared with the amorphous carbon produced by EVA at high temperature,the addition of ceramic-forming filler flux and flame retardant makes the system react at high temperature,producing ceramic body mainly composed of amorphous carbon,SiO₂,Al₂O₃,and TiO₂.The effects of the three processes on the properties of composite materials?hardness,compressive deformability,tensile strength,elongation,tear strength?were explored,the main reason for which is reflected in the degree of mixing.More defective structures were formed during the viscous drag of twin screws in the P1 and P2 processes.The P3 process with a single mixing procedure has a better mixing effect.The addition of coupling agent can increase the mechanical properties of the composite material system.In this experiment,it was found that the silane coupling agent KH-570 had the best effect on enhancing the system performance.In the best formula?EVA 80 phr,EPDM 20 phr,silica black 25 phr,zinc oxide 3 phr,stearic acid 2 phr,paraffin wax 5 phr,polyethylene glycol 6 phr,BIBP 2.5 phr,silane coupling agent KH-570 6 phr,wollastonite 36 phr,talc 24 phr,flux 50 phr,melamine polyphosphate 25 phr,aluminum hypophosphite 25 phr,?and process conditions?P3 process,processing temperature: 95?,processing time: 20 min?.The hardness of the ceramicized EVA flame retardant material is 84?shore A?,the compression set is 11.3%,the tensile strength is 6.91 MPa,the elongation at break is 235%,and the tear strength is 26.9 KN/m.