Preparation,Properties And Application Of A New Type Of PP-Based Wood-Plastic Composites

Polypropylene(PP)is a kind of petroleum based engineering plastic with excellent performance and huge output,but it has some problems,such as consumption of petroleum resources,difficulty in degradation and inability of direct 3D printing.WPC is a new biodegradable material developed rapidly,which is widely used in furniture,packaging,building materials and other industries.In recent years,fused deposition molding(FDM)3D printing has developed rapidly,but there are few 3D printing materials at present,which has become the bottle neck of the development of 3D printing industry.It has good theory and application value to develop polypropylene WPC and FDM wood-plastic materials with high added value.The properties of polypropylene,wood powder(WF)and lignin(L)are very different.WPC needs to modify wood powder and lignin to improve their compatibility.FDM printing materials need to solve the PP printing easy warping,printing difficult problems.In this paper,the preparation methods and properties of WF/PP and L/PP composite based on PP were discussed.In this paper,the effects of different fillers such as wood powder(WF)and lignin(L),modification methods,compatibilizer PP-g-MAH on the properties of WF/PP and L/PP wood-plastic composites were mainly studied.The screw extruder was used to prepare composite materials by melting blending extrusion,and MFR,thermal deformation temperature measuring instrument(HDT),TG,FTIR,SEM,universal testing machine and contact angle were used to test and characterize the composite materials,and then the 3D printing performance was tested on FDM 3D printer.Firstly,the composite system named WF/PP was studied.The selection of NaOH solution concentration in normal temperature alkali treatment of wood powder was studied,and self-made compatibilizer(PP-g-MAH).The effects of wood powder content,modification method of wood powder and compatilitizer content on physical and chemical properties and mechanical properties of WPC were investigated,and then the performance of the printed device was improved by graphite-coated microwave method.The experimental results showed that in the normal temperature alkali treatment of wood powder,when NaOH solution concentration was 18 wt%,the treatment of wood powder was better.When the content of wood powder is 25 wt%(based on PP substrate quality)and the content of PP-g-MAH of compatibilizing agant is 12 wt%,it is a better injection formula.Compared with pure PP,the mechanical properties of WPC have been improved by 35.6%,56.0%and 16.6%,respectively,in terms of tensile strength,bending strength and impact strength.Due to the requirements of FDM filament on the properties of composite such as MFR and tensile strength,15 wt%of A-K-WF and 8 wt%of compatibilizer PP-g-MAH were selected as the silk formula for 3D printing,and the printed finished products had better quality.At last,the technological conditions of graphite coating microwave strengthening method for 3D printing devices were discussed.Under suitable microwave treatment,the tensile strength and modulus of 3D printing devices were increased by 54.1%and 59.2%,respectively,compared with those before treatment.Secondly,the system of L/PP WPC was investigated.The effects of lignin content,lignin modification method,nucleating agent content and toughening agent SEBS content on the properties of WPC were investigated,and then the suitable formula of composite material was determined.The results show:when lignin content increases,the tensile modulus,bending strength and bending modulus of WPC increase,the tensile strength first increases and then decreases,and the impact strength and breaking elongation decrease.When lignin content was 15 wt%,the MFR value of WPC was 9.16 g/l0min.When the content of alkylated modified lignin(A1-L)was 15 wt%,the bending strength,tensile strength,impact strength and elongation at break of WPC were 43.70 MPa,30.34 MPa,26.50 kJ/m2 and 85.8%,respectively,which were increased by 9.1%,4.5%,15.4%and 315.1%compared with L/PP.When the nuclear agent content is 0.2 wt%,toughening agent SEBS content is 15wt%,and AL-L content is 15 wt%,the bending strength,impact strength and elongation at break of WPC are 49.93 MPa,28.65 kJ/m2 and 152.1%,respectively.Compared with L/PP WPC,the bending strength,impact strength and elongation at break of WPC are increased by 24.7%,24.8%and 635.8%,respectively.The extrusion performance and printing performance of this formula composite material are also greatly improved.