Preparation And Properties Of Flame Retardant Polyurethane/Wood Flour Foamed Composite Materials

Polyurethane/wood flour foamed composite material is a new type of foamed material,its flammability limits application scope,so it's very important to improve its flame retardancy.Flame retardant FWPC was prepared in this study.Cone calorimeter(CONE)was used to study flame retardancy of FWPC.Thermal gravimetric analyzer(TG)was used to study thermal stability.Field emission scanning electron microscopy(FE-SEM)and X ray spectrometer(EDS)were used to observe the interfacial bonding and analyze the element type and content.We had used infrared spectroscopy(FTIR)to study the changes in internal group.The results are as follows:(1)Single factor experiment method showed that,FWPC had better flame retardancy when more ammonium polyphosphate(APP)was added.When 15%APP was added,24 h water absorption of material was 32.89%,compressive strength was 2.25 MPa,ignition time was prolonged by 25%,heat release rate(HRR)decreased 8.9%,residual carbon amount increased 19.76%,smoke density value was 74.79,which was just in line with national standard GB 20286-2006(SDR<75).(2)Compared with nonflame retardanted FWPC,whether FWPC made with APP added directly or FWPC made with wood flour treated by APP solution,TTI of FWPC was extended by 25%and 62.5%.The former had lower smoke release performance,water absorption and mechanical property,the latter had better safety performance,such as more residual weight.(3)Flame performance of FWPC was further improved by adding 4A molecular sieve.When 3%4A molecular sieve was added,24 h water absorption reached the lowest value(48.75%),maximum compressive strength reached 3.03 MPa,TTI was delayed by 83.33%and residual carbon weight increased 1.53%.At this time,FWPC had optimal comprehensive performance.(4)TG analysis showed that the initial pyrolysis temperature of FWPC treated with APP and 4A molecular sieve was 91 0C,residual weight was 37.20%,which had better thermal stability than FWPC treated with APP alone.Observed by FE-SEM,FWPC treated with APP and 4 Amolecular sieve had small pore diameter and thickening pore wall.EDS showed that in addition to C,O,Cl,Si,FWPC also appeared N and P elements of APP and Na and Al trace elements of 4A molecular sieve.FTIR showed that FWPC treated with APP and 4A molecular sieve had no absorption peak at 2278 cm-1 and 512 cm-1,which indicated that they could react with polyurethane or silane coupling agent in polyurethane/wood flour foamed composite materials,so as to enhance the mechanical properties of composite materials by combining the chemical bond effect.