Research On The Pressing Crafts And Strengthening Mechanism Of Composite Materials Made From Eucalyptus Veneer And Polypropylene(PP) Film

Eucalyptus is one of the major plantation species which is largely planted in China and polypropylene(PP) is an excellent thermoplastic resin material.Eucalyptus veneer and polypropylene(PP) film are used as the raw materials to make wood-plastic composites materials in this study,the impacts of hot pressing process parameters such as pressing temperature, pressing pressure, pressing time and the amount of plastics on the bonding strength of this composites materials were analyzed systemly and optimized the process parameters.The physical and mechanical properties of eucalyptus veneer/polypropylene film composites were compared with three layers urea-formaldehyde resin plywood. The impact of modification by silane coupling agent (KH550) and maleic anhydride grafted polypropylene (MAPP) on the physical and mechanical properties and strengthening mechanism of composite materials were studied. The main conclusions are as follows:(1) The wood-plastic materials made from eucalyptus veneer and polypropylene(PP) films are feasible and it’s environmentally friendly without formaldehyde released.The pressing temperature has a great influence on the bonding strength, when it rose from 165℃ to 180℃,the bonding strength kept increasing; Within the selected factor level, the impact of pressing time on the bonding strength is significant, but the impact of pressing pressure and PP films are not.The optimum parameters were under the pressing temperature of 180 ℃,pressing pressure of 0.9 MPa, pressing time of 70s/mm and PP films of 150g/m2.On that condition,the bonding strength of thermoplastic resin plywood were tested again, and the physical and mechanical properties of the new type wood-plastic composites could reach the demand of GB/T9846.3-2004 standard plywood I,and accurate coefficient was 3.56% which was less than 5%.(2) The physical and mechanical properties of the eucalyptus veneer/polypropylene (PP)films composite materials are more excellent, which bonding strength Ⅱ were 49.61% higher than the UF plywood, the static bending strength (MOR) and the elastic modulus (MOE) values were 15.58% and 6.69% higher than UF plywood.After soaking 168h, the thickness swelling of UF plywood was 12.23% higher than veneer/polypropylene (PP)films composite materials.The average and maximum formaldehyde emission of veneer/polypropylene (PP)films composite materials were less than 0.3 mg/L which reached F requirements.(3) After treated with coupling modification, the interface bonding strength of composite materials were improved, modification effect of MAPP was better.The right amount of coupling could improve the MOR and MOE of composite materials, but excessive coupling dosage will reduce the bending performance.(4) After scanning electron microscopy analysis, it was found that interface compatibility of MAPP and KH550 treated composite materials were improved, polypropylene (PP) films molecules penetrated into the cracks of eucalyptus veneer tubes and cells, the eucalyptus veneer and polypropylene (PP) films were formed closely, thus the bonding interface strength was strengthen.