Preparation And Properties Of Thermoplastic Polyurethane Based Elastic Wood Plastic Composites

Thermoplastic Polyurethane(TPU)is a kind of elastomer material with excellent performance and wear resistance,its research and applications have attracted more and more attention.However,traditional raw materials of TPU are derived from petroleum,existing resource shortage,non-renewable,difficult to degrade and other problems,which restrict their applications.Wood-Plastic Composite(WPC)has developed rapidly in recent years due to its good degradability.Wood flour and other biomass residues from agricultural and forestry processing are widely sourced and cheap.In order to reduce the cost and improve the degradability of TPU,this paper discussed the preparation and properties of elastic wood-plastic composite based on Wood Flour(WF)and TPU.It has both the advantages of TPU and WPC,such as good elasticity,low cost and good degradability.Firstly,this paper studied the synthetic methods of thermoplastic polyurethane.We chose polytetrahydrofuranediol(PTMG)as soft segment material,isophorone diisocyanate(IPDI)and 1,4-butanediol(BDO)as hard segment raw materials to synthesize TPU by prepolymer method.The effects of relative molecular weight of soft segment,reaction temperature,hard segment content and isocyanate index on the mechanical properties of TPU were investigated,then the suitable synthesis conditions were determined.The synthesized TPU was characterized by FT-IR,~1H-NMR,XRD,GPC,SEM,AFM,TG,and DSC,and its mechanical properties were tested.The results were as follows:the optimum synthesis conditions were that prepolymerization temperature 80℃,curing temperature 90℃,prepolymerization time 2h,hard section content 42wt%,soft section molecular weight 2000,isocyanate index 1.04;FT-IR,~1H-NMR and GPC results confirmed that the target product of thermoplastic polyurethane with appropriate molecular weight was synthesized successfully;SEM and AFM images showed that TPU had good microstructure and microphase separation structure;TG and DSC analysis showed that the initial decomposition temperature,melting temperature and glass transition temperature of TPU were 297℃,170℃and-25℃,respectively,indicating that the TPU had good thermal stability and excellent processing performance,which laid a good foundation for the preparation of TPU-based WPC.Then,the wood flour was added into the TPU synthesis system for in-situ polymerization,and the TPU-based WPC was prepared by melt blending extrusion with lubricant and antioxidant as additives.The effects of wood flour particle size,content,modification methods and lubricants on the properties of TPU-based WPC were investigated.The materials were characterized by SEM and TG,melting index(MFR),water absorption,and the mechanical properties were tested.The results showed that WF particle size had great influence on the interfacial bonding and mechanical properties of WPC,and the suitable particle size of wood powder is 200mesh;considering the thermal stability,melt flow performance,water absorption and cost factors,the optimal content of wood powder in WPC was 15wt%;when the content of zinc stearate was 5wt%,the tensile properties of the composite were the best;the WPC prepared by acetylation modified wood powder,alkali treatment at room temperature and k H-550 coupling agent modified wood powder had good mechanical properties,their tensile strength were 15.12MPa and 12.19MPa,and their elongation at break was more than 800%;TG analysis showed that TPU-based WPC did not decompose at 250℃,meaning the TPU-based WPC was suitable for melt extrusion.Finally,WF/TPU and WF/PLA/TPU based elastic wires were prepared by screw extrusion of TPU based WPC and additives,and 3D devices were prepared by selecting appropriate printing parameters.The feasibility of 3D printing of TPU-based WPC composites was preliminarily discussed.It was found that the WF/PLA/TPU composite wire had good appearance and printing performance,and the prepared 3D model devices were elastic.