Study On Wood Plastic Composites Based On Polyolefin Modified By Wood Flour Or Corn Straw For 3D Printing

Wood plastic composites are a kind of low cost,biodegradable and environmentally-friendly material,which is mainly used by injection moulding.3D printing is a recently rapidly growing manufacturing process,but there are fewer 3D printing materials,which becomes the bottleneck of the 3D printing industry.So it is urgent to develop high value-added wood plastic composites suitable for 3D printing.In this paper,the preparation process and properties of both modified wood flour(WF)/polyolefin and corn straw/polyolefin wood plastic composites FDM filaments were discussed.Firstly,a kind of wood plastic composites(WPC)filament for fused deposition molding(FDM)was prepared by ball milling and screw extruding a mixture of polypropylene(PP),linear low density polyethylene(LLDPE)matrix,acetylated wood flour(AWF),talcum powder,nano SiO2,and other additives.The influences of the matrix ratio and the wood powder ratio on the properties of materials were investigated.Thermal stability,fluidity,mechanical properties and microstrucuure were characterized by using simultaneous thermogravimetric-differential thermal analysis system,vicat softening point tester,melt flow rate meter,and universal mechanical testing machine.The testing results showed that the optimum m(PP)/m(LLDPE)ratio was 35:65.With the increase of the weight percentage of AWF in the WPC,the tensile strength,flexural strength,and flexural modulus of the WPC firstly increased and then decreased.The material prepared with 30wt%of AWF reached the highest tensile strength(24.5 MPa),bending strength(23.3 MPa),and elastic modulus(1023.3 MPa).The addition of wood powder raised the heat deformation temperature of the WPC.The WPC with 20wt%-30wt%of AWF had relatively higher deformation temperature.The prepared WPC filaments were tested on a 3D printer.The 3D printing test results showed that the acetylated wood flour/polyolefin wood plastic FDM filaments could be extruded smoothly,and the printing effect was better.Secondly,the 3D printing filments were prepared by single screw-extrusion with PP-LLDPE as matrix,modified corn straw powder as reinforcement filler,mica powder and polyethylene wax as additives.The goal is to investigate the effects of the content of modified corn straw powder,mica powder and polyethylene wax on the properties of composites and to carry out relevant characterization tests on the WPC.Results showed that the best mechanical properties of the WPC was prepared by adding 30wt%modified corn straw powder and 15wt%mica powder.The tensile strength,bending strength,bending modulus and impact strength were respectively 18.9MPa,27.1MPa,1197.8MPa and 10.2KJ/m2.With the corn straw powder increased the heat deformation temperature of the composites was gradually increased.The fluidity results indicated that melt index of composites with 3wt%of polyethylene wax were optimal.But the fluidity of the WPC was gradually deteriorating when the content of corn straw powder continually increased.The 3D printing test results showed that the smooth and unbroken filament in the printing of wood plastic composites filament with 10wt%,20wt%,and 30wt%of modified corn straw powder could meet the mechanical properties and liquidity requirements of 3D printing.