Study On Preparation And Properties Of The Polystyrene Board Coated By Halogen-free Flame Retardant

Polystyrene foam(EPS)plastic has the low coefficient of thermal conductivity and the low water absorptionstability because of its rigid characteristics and closed pore structure.It has the light weight,low cost,good stability and the mature construction technology,which has widely used in exterior wall thermal insulation system as a structural material.But traditional polystyrene foam board will melt and shrink when in fire,and the drop will ignite the nearby in the combustion process.The oxygen index of polystyrene foam is only 18 %,and the hidden trouble in security has aroused attention when used in the construction.So,it is inevitable to develop the high fire rating polystyrene foam board.In this paper,we studied a new coating method to make a kind of halogen-free,environmentally friendly,good flame retardant and perfect mechanical properties of exterior wall thermal insulation material,which could solve the problem of the limiting in adding the retardant in the phase of suspension.Otherwise,we also solve the traditional foam insulation board's problems of low adhesive property,poor flame retardant property and release harmful gas combustion when burning,and explore the mechanism of flame retardant.The experiment use halogen-free alternative expanded graphite(EG)and ammonium polyphosphate(APP)as flame-retardants,use the phenol-formaldehyde resin as the adhesives and make special curing agent.We use the new moulding method called “wet moulding”,which can more efficient use of the cross-linking process of the phenolic resin,which improved the flame retardant properties and adhesion performance immensely.The homemade pre-expander container,mixing equipment,molding mold and equipment was made.The molding process is carried out by simulating the actual production of the factory,and optimizing the whole process to improve it in order to choose the best molding process method and the process conditions by many experiments.The mechanical properties,oxygen index,thermal degradation,microstructure,structure were also be tested,the mechanism of flame retardant was explored.(1)The results indicated that,the best mass ratio of EPS,phenolic resin(PF)and curing agent was 100:90:20.Using phenolic resin coated on polystyrene foam could effectively improve the mechanical properties of the material,and the LOI was rised from 18 % to 27.9 %,the compression strength was increased by 326 %,the tensile properties was increased by 25 %,and solved the problem of melting when heatd and burning poor performance with molten drops of the EPS significantly.(2)When the polystyrene foam insulation board was retardanted by the halogen-free retardant EG,the flame retardant performance further increased.When the mass ratio of EPS,phenolic resin,curing agent and EG was 100/90/20/4,the mechanics of the EPF/EG maiterial performs best,and the LOI reached 29.4 %.The FTIR experiments shows that there is no chemical reaction between EG and PF,they were all covered on the surface of EPS particle.The phenolic resin cut off the oxygen and heat into the substrate by the crosslinking curing structure,while EG was expanded to carbon layer when heated,which could have the effect of oxygen insulation and heat insulation.The EPF/EG material has complete cell structure with the EG and PF protect the substrate all together,which could improve the flame retardant properties.The TG experiment showed that EG/PF could improve the stability of the materials,and EG could improve the rate of carbon residue of material to some extent.(3)The material of EPF/EG/APP had the better mechanics performance when use the compounded fire retardant EG/APP,and the mass amount of EG was 4 phr,the mas amount of APP was 8 phr.The tensile strength and compression strength was 0.31 MPa and 0.109 MPa,respectively.The flame retardant performance is better,the LOI value reached 33 %.The material also had the better thermal stability,the carbon layer were more stable and the rate of carbon residue is more higher.Otherwise,it can effectively reduce the heat release rate and decrease the release of the CO.