| Wood-Plastic Composites(WPC)are a new type of green material that can replace wood products and plastics in many fields,enabling wood chips,biomass residues and waste plastics to regain their value.However,compared with pure wood,WPC has a poor wood texture,and due to the influence of production processes,material properties and use environment,WPC has problems such as lack of aesthetic appearance and non-aging resistance,which limit the service life and application scope of WPC.In this paper,cotton and linen fabric,PP decorative film,Teslin mesh fabric and a variety of coatings are selected as surface decoration materials to explore the methods,effects,and,ageing resistance,of decorative wood flour/high density polyethylene(WF/HDPE)composites.Through the characterization,performance testing and analysis,the main conclusions drawn in this thesis are as follows:1.Properties of the fabric laminated WF/HDPE compositesThe surface decorative WF/HDPE composites with "fabric-HDPE-WPC-HDPE-fabric" structure were prepared by hot pressing using HDPE powder as the bonding material instead of adhesive.The surface bonding strengths between WF/HDPE composites and fabric was 1.51 MPa(WF:HDPE = 6:4)and 1.42 MPa(WF:HDPE = 7:3)respectively,and no peeling occurred after impregnation.The mechanical property test results showed that the bending strength of fabric covering WF/HDPE composites slightly increased,but the tensile strength decreased,comparing to uncovered WF/HDPE.2.Fabric lamination by melt and penetration of the surface polymerThe thermoplastic polymer powder was spread on the surface of the fabric to form a structure of "thermoplastic polymer-fabric-WPC-fabric-thermoplastic polymer",and the fabric is adhered to the surface of the substrate through the melting and penetration of the surface polymer during hot pressing.Based on the microstructure observation and performance testing and analysis,these results were obtained: the cotton and linen fibers are loose and easily permeable,relying on the HDPE on the surface of the substrate and the penetration of the surface thermoplastic polymer could form a strong bond to the decorative fabric;the fibers of the fabric were pressed into a flattened form after hot pressing,and the hot-pressing temperature significantly affects the lamination effect.The temperature of 160°C is the appropriate temperature.The embedded effect of the cotton and linen fibers results in a very high surface bonding strength and flexural strength,with a surface bonding strength of 4.57MPa(hot pressing temperature of 180°C,WF:HDPE = 6:4,thermoplastic polymer was PLA)and a flexural strength of 82.19 MPa,with a flexural modulus of 4.34 GPa(hot pressing temperature of 160°C,WF:HDPE = 7:3).This approach is also applicable to thermoplastic polymers such as polybutylene succinate(PBS)and polymethyl methacrylate(PMMA),enabling the preparation of fabric laminated decorative WF/HDPE composites that are biodegradable,transparent and have good mechanical properties.3.PP decorative film lamination technology and its effect on the properties of WF/HDPE compositesThe surface decoration of WF/HDPE composites(WF:HDPE= 6:4 and 7:3 respectively)after surface sanding was carried out using PP decorative film with imitation wood grain as the surface decoration material.And thermoplastic Polyurethane(TPU)and Polyether sulfone(PES)adhesive film as the bonding material respectively.The test results showed that the surface bonding strength of the PP decorative film to the substrate is greater than 1.0 MPa at a hot-pressing temperature of 140°C.The water resistance is good and the bending strength was improved.After PP decorative film veneering,the tensile strength of the substrate with WF to HDPE ratio of 6:4 is improved,but the tensile strength of the substrate with WF to HDPE ratio of 7:3 is reduced.4.Aging performance of coated WF/HDPE compositesA variety of paints were used to decorate the surface of the wood-plastic composite material.The appearance of the paint film,performance and ageing tests revealed that fluorocarbon paint,acrylic polyurethane paint and marble-like paint all had good decorative effects on the wood-plastic substrate.The results of the paint film adhesion test showed that the marble-like paint was able to achieve the best grade(grade 0)and the rest of the paints had a grade 1 adhesion.The results of the water contact angle test show that the acrylic polyurethane topcoat has the best water resistance.The UV artificially accelerated ageing treatment showed that all the finishes faded after a long ageing test,and the bending strength decreased with the ageing time.Among them,the marble-like paint finish WF/HDPE board had the lightest fading and the highest bending strength retention rate of 95.75%.The comprehensive analysis showed that the acrylic polyurethane topcoat and the marble-like paint have better ageing resistance.5.Ageing resistance of Teslin mesh laminated WF/HDPE compositesThe decorative WF/HDPE composites was prepared using HDPE powder,TPU and PES adhesive film as the bonding materials respectively,and Teslin mesh as the surface decorative material.The preparation process and the effect on the ageing resistance was investigated.The test results showed that the HDPE powder enables the Teslin mesh to bond firmly with the substrate,and the surface bonding strength can reach over 1.0 MPa.The bending strength of WF to HDPE ratio of 6:4 and 7:3 WF/HDPE composites was increased by 31.16% and 4.80%respectively.While the bonding of TPU and PES films to Teslin fabric was weak,the surface bonding strength was less than 1.0MPa and reduced the bending resistance of wood-plastic substrate.After artificially accelerated ageing by UV fluorescent light,the surface of Teslin mesh faded,and the longer the ageing time,the more obvious the color change of Teslin mesh.When the TPU adhesive film was used as the bonding material,the bending strength retention rate of the laminated wood-plastic substrate was the highest after 1000 h.The bending strength retention rates of the WF to HDPE ratio of 6:4 and 7:3 substrates were 82.18% and 80.62%respectively,reaching the requirements of Class I wood-plastic decorative panels. |
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