Study On Low Density And High Intensity Core-shell PVC Foamed Wood-plastic Composites

Wood-plastic composite material is a new type of plant fiber material emerging in the world in recent years.The development and application of WPC are of great significance to the reuse of wood processing residues and the search for substitutes for solid wood.It is also an effective way to recycle plastics and solve white pollution.This project mainly uses polyvinyl chloride resin, wood flour,foaming agent,coupling agent,and other various additives as raw materials,and uses SJZ45/100 conical twin-screw extrusion equipment to coextrude the multilayers of plastics processing.Combining the process and rigid plastic crust foaming technology,a core-shell PVC foamed wood-plastic composite material was prepared,and its microstructure,apparent density and mechanical properties were characterized.In the core layer,the foaming process is adopted to reduce the density,and the surface layer structure is added with glass fiber to enhance the strength,so as to prepare a lightweight,high-strength wood-plastic composite material.The main research content:?1?Study on the modification of organic foaming agent AC reduces the decomposition temperature of AC foaming agent and reduces the amount of heat released.The modified foaming agent is applied to the preparation of core-shell PVC foamed wood-plastic composites.?2?To study the relationship between the amount of modified foaming agent and the properties and microstructure of PVC foamed wood-plastic composites;?3?to study the effect of wood flour addition and wood flour particle size on the properties and microstructure of PVC foamed wood-plastic composites;?4?The core-shell PVC foamed wood-plastic composites were prepared by co-extrusion technique,and their microstructure,mechanical properties and apparent density were characterized.?5?GF was added to the shell to study the effect of different content of glass fiber and different aspect ratio on the performance of core-shell structural wood-plastic composites.Through the research of this topic,we reached the following conclusions:?1?The AC foaming agent was modified by ZnO and NaHCO₃,and the absorption-exothermic composite foaming system was prepared at a ratio of AC:ZnO:NaHCO₃ is10:2:20.The decomposition temperature was 150-185?.The endothermic reaction of 264KJ/g solves the disadvantages of high decomposition temperature and large heat release of pure AC foaming agent,and a composite foaming agent suitable for PVC wood-plastic composite foaming is prepared.?2?Experiments proved that 2wt%is the most suitable amount of foaming agent added.When the amount of the modified absorbing-exothermic foaming system is 2wt%,the material has a good cell structure,and the lowest density is 0.68g/cm³,which is 38%lower than the material without foaming agent added.The impact strength was 8.56 KJ/m²,an increase of24.8%over the material without foaming agent added.The addition of the modified foaming agent slightly reduces the toughness while increasing the strength of the material.When the amount of the foaming agent is too large,defects such as a rise in material density and a drop in impact strength due to the merging and collapse of cells occur.?3?The particle size of wood flour has a great influence on the properties of the material.With the decrease of the particle size of the wood powder,the bending strength of the material rises first and then decreases.When the particle size of the wood powder is 200 mesh,the bending strength has a maximum value of 18.7 KJ/M²;the impact strength decreases,and the wood powder decreases.The smaller the particle size is,the more obvious the impact strength decreases.The density of the material decreases first and then increases with the decrease of the wood flour particle size.When the wood flour particle size is 200 mesh,the minimum density is0.68g/cm³.There is a significant reduction in the filling of 80 mesh wood flour.?4?The increase of wood flour dosage has a significant inhibitory effect on the foaming effect of PVC wood-plastic composites.With the increase of wood flour content,the density of the material is on the rise and the higher the content,the greater the increase,40wt%wood flour filling.When the amount is,the density at which the density density is 1.03 g/cm³ is far greater than the wood powder loading of 10 wt%,which is close to the density of unfoamed PVC wood-plastic materials.The increase of wood flour content has a significant effect on the mechanical properties of the material.With the increase of wood flour content,the impact strength,tensile strength and bending strength of PVC foamed wood-plastic composites have a tendency to decrease.?5?Co-extruded technology was used to prepare core-shell structure PVC foamed wood-plastic composites with a surface layer of pure PVC resin.In the core-shell structural wood-plastic composite structure with uniform PVC foamed wood-plastic composites,the presence of the shell layer slightly reduces the toughness increase of the wood-plastic material.The performance is that the impact strength has increased,and the bending strength and tensile strength have decreased.When the ratio of wood to plastic was 2:8,the impact strength of the core-shell structure wood-plastic material increased by 8.5%,the tensile strength decreased by2.6%,and the flexural strength decreased by 3.2%.?6?The length of the glass fiber has a greater impact on the core-shell structure of PVC foamed wood-plastic composites.The longer the fiber length,the better the mechanical properties of the material.When the fiber length is 5mm,the tensile strength of the composite material reaches 22.9.MPa,the impact strength is 10.47KJ/M²,the fiber is too long will cause a fracture under the shear stress of the extruder,resulting in a decline in the mechanical properties of the material.?7?Within a certain range,with the increase of glass fiber content,the impact strength,tensile strength and bending strength of core-shell PVC foamed wood-plastic composites are improved to varying degrees,and the added amount is 15wt%.When it reaches the maximum value.Continuing to increase the content of the glass fiber will cause deterioration of the mechanical properties of the material due to fiber agglomeration or poor interface bonding between the fiber and the PVC resin matrix.