The Preparation And Mechanism Study Of Flame Retardant Polystyrene Foam Insulation Board

Expanded Polystyrene(EPS)foam is the widely applied closed cell foam material on building heat-insulating layers,packaging and on-water floating,due to the outstanding properties of its heat insulation,corrosion resistance,moisture proof,sound insulation,shock absorption,etc.Recently,serious concentration has been drew on EPS foam because inmost cases,its high flammability has always been a driving force to a fire.The EPS foam,essentially consisted of polystyrene and air,having the typical foam properties of being porous and thin-walled,having a large surface area and a content of air higher than 98%of the whole volume,which makes the flammability even higher compared with its bulk material.Therefore,in order to meet people's daily demand,the improving of the flame retardancy of EPS foam is now a pressing need.A brand technology of flame retardant coating was carried out in the subject to achieve the modifying of the EPS foam.The thesis was divided into three parts:First,the experimental apparatus on the preparation of EPS was described,and the method as well as best experimental conditions was explored.Spontaneously,the flame retardancy was improved by coating the intumescent flame retardants ammonium polyphosphate(APP),pentaerythrotol(PER),and melamine(MEL)on the pre-foamed EPS beads with melamine modified urea formaldehyde(MUF)as the coating solvent.The Fourier Transform Infrared Spectroscopy(FTIR)was displayed that the characteristic peaks of MEL appeared within the range of MUF,and the content of the free formaldehyde in MUF was 0.15%,which was obviously lower than that in the UF.The flame retardancy and thermal stability of the flame retardant EPS were characterized by the limit oxygen index(LOI),vertical combustion(UL-94),cone calorimeter(CONE)and thermogravimetric analysis(TG),the experimental results showed that with the increase of the amount of additive flame retardants,the LOI value of the material also increases.When the dosage of the traditional flame retardant was 80(100 for EPS foam),the LOI result could reach to 36.3%,and the amount of residual carbon was 14.8%,as the density of smoke was reduced and the burning rate was obviously slowed down.The thermal contraction of the foam was eased.Secondly,montmorillonite,molybdenum disulfide and expandable graphite(EG)were introduced into the flame retardant system and mixed with zinc borate(ZnB).The experimental results showed that there existed a synergistic effect between zinc borate and those two-dimensional materials,which was reflected in the increase of LOI value and residue char amount,decrease of smoke density and improvement of char structure.Among the three two-dimensional materials,expandable graphite showed the best synergistic effect with zinc borate.When the ratio of EG and ZnB was 2:1 and additive amount was 24 phr,the LOI value could reach up to 32.6%and passed V-0 rating in UL-94 test.The amount of smoke release was dropped dramatically and the residue char was significantly improved,as well as thermal stability.Finally,multi-walled carbon nanotubes(MWNTs)were surface modified by introducing aluminum to prepare Al-MWNTs.The obtainedAl-MWNTs was mixed with expandable graphite(formula of both two-dimensional and one-dimensional structures),to improve the flame retardant properties of EPS foams.The results of X-ray photoelectron spectroscopy(XPS)and FTIR has proved that Al was successfully grafted onto the surface of MWNTs.When the ratio of expandable graphite and modified carbon nanotubes was 7:2,and the additive amount of flame retardants is 36 phr,the combustion performance of EPS samples were greatly improved.The LOI value reached up to 30.3%,and passed V-0 rating in UL-94 test.The peak heat release rate of treated foams decreased from 932.8 kW·m-2 to 177.5 kW·m-2.After combustion,the char layers became more compact,which could effectively isolate matrix and oxygen,preventing the further spread of flame.Meanwhile,the smoke suppression was also improved significantly.Two different dimensional nano particles could support each other and improve the structure of char layer,resulting in an enhancement of fire resistance.