Study On Properties Of Composites Materials Prepared By Waste Polypropylene Filled With Biomass Straw

The wood plastic composites(WPC)is made of plastic as matrix,the wood fiber as reinforcing filler,and the additive is added.In the early stage of WPC research,the selected wood fiber was mainly wood powder.In recent years,with the scarcity of forest resources and the improvement of people's environmental awareness,the abandoned biomass has been gradually concerned by researchers.In this thesis,waste polypropylene(WPP)is used as matrix,sorghum straw fiber(SSF)and sugarcane straw fiber(SCF)as reinforcing filler.The waste polypropylene composites filled with biomass straw were prepared by extrusion injection molding.Firstly,the effects of kinds and contents of both straw and auxiliaries on the mechanical properties and on flame retardancy of composites were investigated.The effect of composite coupling agent(KH550/TCA201)on the properties of composites was mainly explored.The results showed that when m(WPP):m(SSF): m(POE-g-MAH)=100:30:8 and composite coupling agent(KH550:TCA201=1:1)content was 2 phr,the mechanical properties and flame retardancy of sorghum straw filled waste polypropylene composites(WPP/SSF)were excellent.The SCF was treated with 2 % NaOH solution and then modified with 2 phr KH550/TCA201 composite coupling agent,while adding 8 phr PP-g-MAH,SCF filled WPP composite material(WPP/SCF)was prepared with the best performance.Secondly,the thermal stability and pyrolysis mechanism of biomass straw,WPP and waste polypropylene / biomass straw composites before and after modification were investigated under nitrogen atmosphere.It demonstrated that the thermal stability of WPP matrix was increased by adding SSF and modified SSF(MSSF),and the residual carbon rate of WPP/MSSF and WPP/SSF composites increased by 66.6 % and 39.5 % compared with WPP,respectively.The overall thermal stability of WPP/MSSF and WPP/SSF composites were positively related to the flame retardancy.The flame retardancy of the composites increased with the increase of the overall thermal stability of the composites.Finally,the composites were pyrolyzed by thermogravimetric analyzer(TG)and fixed bed.FTIR,GC-MS and SEM-EDS were used to analyze the chemical composition of the gas phase,liquid phase and solid phase products during the pyrolysis of the composite material.The results indicated that the products of the gas phase were mainly consisted of alkanes,alkenes and a few aldehydes,ketones,phenols and other compounds.The types and contents of gases produced during the pyrolysis of composite material were much lower than those of biomass pyrolysis alone.Pyrolysis oil was mainly composed of long-chain alkenes and alcohols,with a small amount of compounds containing fluorine,chlorine and other pollutants.A small amount of fluorine and chlorine were also found in the residual carbon.Both the pyrolysis temperature and the pyrolysis form have influence on the yield and distribution of fluorine and chlorinated compounds in residual carbon.With increasing temperature,the content of pollution elements in residual carbon increased,and the content of pollutants in residual carbon at slow pyrolysis was higher than that in fast pyrolysis.