Preparation And Mechanisms Of Halogen-free Flame Retardant Microencapsulation Of Polystyrene Foams

As a low-cost polymer material,expandable polystyrene foams(EPS)is widely used in buildings,packaging,bridges,automobiles and other fields because of its excellent thermal insulation,moisture resistance,cushioning and light weight.However,EPS is highly flammable because of its hydrocarbon-rich structure and high surface area,which will generate heavy smoke and molten droplets during combustion.This seriously restricts in its application.This work designs three types of halogen-free flame retardants to endow the flame retardant properties of EPS according to the principles of safety,simple process and environmental friendliness.Main methods are as follow:(1)Phosphorylated chitosan(CA)was prepared to obtain the CA coated EPS foam(E-CA)by resin bonding.As the results shown,with 20 g CA coating on 25 g EPS foam,the limiting oxygen index(LOI)of EPS increased to 33.5 and reached V-0 rating in vertical burning test(UL-94).According to the results of the cone calorimetry(CONE)test,the peak of heat release rate(pHRR),the total heat release(THR),the peak of smoke production rate(pSPR)and the total smoke production(TSP)were decreased by 51.8%,46.3%,42.9% and 48.7% respectively.To sum up,CA represented better flame retardant performance compared with traditional IFR coated EPS.(2)Boric acid modified sodium silicate coating(BSPS)was used to replace the traditional adhesive resin and combined with expandable graphite(EG)to obtain the BSPS/EG coated EPS foam.When the combination of BSPS and EG were 22:3(25 g),the LOI of EPS increased to 29.5 and achieved UL-94 V-0 rating.The pHRR,THR,pSPR and TSP were decreased by 68.9%,31.3%,42.5% and 17.1% respectively.BSPS/EG not only improved the flame retardancy of EPS,but also achieved halogen-free,phosphorus-free and formaldehyde-free in coating flame retardant system(3)A triazine intumescent flame retardant(PHTD),which was combined with acid source,char-forming agent and blowing agent,was used as the flame retardant adhesive for EPS.As the results shown,PHTD could be coated on the EPS beads without the help of adhesive resin.When the loading of PHTD reached 18 g,the LOI of EPS reached to 28.8 and passed UL-94 V-0 rating.The pHRR,THR,pSPR and TSP decreased by 74.9%,36.8%,77.3% and55.6%.PHTD coating nearly had no influence on the thermal conductivity and can also improve the compressive strength from 132.2 MPa to 158.7 MPa.