Research On Manufacturing Technology And Application Of EVA Film Reinforced Decorative Wood Veneer

The utilization of thermoplastic resin film,an eco-friendly material,as a flexible reinforcement for decorative wood veneer effectively addresses issues such as poor flexibility,cracking and breakage.Additionally,the plastic film can serve as a thermoplastic adhesive that directly bonds with decorative wood veneer and wood-based panels through hot pressing.This approach circumvents the issues of formaldehyde pollution and bonding deficiencies that arise from using liquid adhesives containing aldehydes.In this thesis,ethylene-vinyl acetate(EVA)film was proposed to prepare EVA film reinforced decorative wood veneer.The composition unit,preparation process,and finishing application were investigated.The main conclusions were as follows:(1)The melting temperature of the EVA film selected in this paper was measured by differential scanning calorimetry(DSC)to be 84.77 °C,and the processing temperature range was initially determined.On this basis,the response surface test was used to optimize the hotpressing parameters of EVA film reinforced decorative wood veneer using flexibility and transverse tensile strength as evaluation indexes.The results showed that the effects of hotpressing temperature,hot-pressing pressure,and hot-pressing time on the flexibility of EVA film reinforced decorative wood veneer was not significant;Hot-pressing temperature,hot-pressing time,and the interaction effects of hot-pressing temperature and hot-pressing pressure had significant effects on the transverse tensile strength.When the hot-pressing temperature was111.95 °C,the hot-pressing pressure was 0.94 MPa and the hot-pressing time was 107 s,the flexibility of EVA film reinforced decorative wood veneer reached 4 ～ 6 mm,which could meet the requirements of profiled surface decoration.The transverse tensile strength reached 2.42 MPa,about 3 ～ 4 times higher than the original wood veneer.Medium Density Fiberboard(MDF)was directly decorated with EVA film reinforced decorative wood veneer.The influence of the hotpressing process on the performance of veneered MDF was analyzed.The results showed that the surface bonding strength of veneered MDF could be significantly improved with the increase of hot-pressing pressure.The best finishing hot-pressing temperature was 100 °C,the hotpressing pressure was 1 MPa and the hot-pressing time was 100 s.Under these conditions,the surface bonding strength reached 0.85 MPa(the standard is 0.4 MPa),and the immersion peeling performance met the standards for Class II veneered panels.Cold pressing was beneficial to further improve the surface bonding strength of veneered MDF.When the cold pressing temperature was 25 °C,the cold pressing pressure was 1 MPa,and the cold pressing time was100 s,the surface bonding strength could be increased to 1.17 MPa.(2)The moisture content has a great influence on the storage and processing of decorative wood veneer.Digitizer software was used to analyze the bubbling(cavity)of EVA film when composited with wood veneers with different moisture content.The mechanical properties and overlaying performance of EVA film reinforced decorative wood veneer was also tested.The results showed that the bulging problem was not significant for EVA film reinforced decorative wood veneer,and the cavity ratio was within 5% when the moisture content was 10% ～ 50%.The mechanical properties of EVA film reinforced decorative wood veneer prepared with different moisture contents varied less.The minimum bending diameter was kept at 4 ～ 6 mm,and the transverse tensile strength reached 0.8 ～ 0.9 MPa.The surface bonding strength of EVA film decorative wood veneered MDF was kept at about 0.8 MPa.To avoid other negative effects such as mildew caused by moisture content,the moisture content of decorative wood veneer should be kept at 10% ～ 20% during actual processing.(3)Different wood-based panels were decorated with EVA film decorative wood veneer to study the suitability of wood substrates.In this thesis,representative medium density fiberboard(MDF)and poplar plywood were used as test objects,and the effects of substrate surface structure,adhesive thickness,and cold pressing factors on their overlaying performance were mainly analyzed.The results showed that the surface bonding strength of veneered MDF and veneered plywood reached 1.17 MPa and 0.93 MPa,respectively.The immersion peeling performance of veneered MDF was not as stable as that of veneered plywood.When the EVA film thickness increased from 0.1 mm to 0.3 mm,the surface bonding strength of the two veneered panels increased by 48.7% and 39.8%,respectively,and the immersion peeling length decreased to 0 mm.Cold pressing could significantly improve the surface bonding strength and immersion peeling performance of the veneered MDF,while the improvement for the veneered Plywood was relatively small.The surface bonding strength of veneered MDF and veneered Plywood were increased by 40% and 10% respectively under the optimized cold pressing process.(4)In this thesis,a micron oligomeric semi-siloxane(MS)solution was prepared by using a silane coupling agent and neutral silica sol in an alkaline catalytic environment to pretreat the surface of poplar plywood,to improve the moisture and heat resistance of EVA film reinforced decorative wood veneered plywood.The results showed that MS pretreatment could form micron-sized caged poly(semi-siloxane)structures on the plywood surface,constructing a rough hydrophobic surface and reducing the polarity of the substrate surface,thus making the plywood substrate more compatible with EVA film.When the content of neutral silica sol was 15%,the surface bonding strength of plywood could reach the optimal 1.49 MPa,which was about 60%higher than that of untreated plywood.The influence of wet and hot environments on the mechanical properties of EVA film reinforced decorative wood veneer was more obvious than that of dry and hot environments.The maximum ambient temperature was 60 ℃ ～ 70 ℃.On this basis,the humid heat cycle test was carried out at a 60 ℃ water bath for 7 days.The results showed that the surface bonding strength of untreated plywood decreased by 83.9% from 0.93 MPa to 0.15 MPa,and the surface bonding strength of plywood decreased by 65.1% from 1.49 MPa to 0.51 MPa after MS pretreatment.