Preparation And Properties Of Aluminum/Wood Decorative Composite

Aluminum/wood composite has developed into a high-end decorative material though itwas applied relatively late in China. It is used widely as functioanl materials of buildings,furniture and vehicles due to its striking advantages, such as decorativeness, toughness,dampproofness, flame retardance, heat insulation and so on. This composite, however, is to bemade with a special and costly adhesive because of the different property of aluminum andwood, and the complexity of their surface pretreatment and hot-pressing. In order to helppromote the new composite, this paper focuses on its hot-pressing process and compoundingmechanism based on the selection of the low-price and high-quality adhesive.In this paper, mechanical and physical properties were studied about the composite whichwas hot pressed by different kinds of modified phenolic resin (PF), then, one modified waywas decided. Orthogonal experiment and single factor experiment, as well as the effect ofmixture ratio on the composite properties, were designed to study systematically hot-pressingparameters. This paper also discusses the mechanism of interfacial bonding betweenaluminum and PF by analyzing the surface free energy, FTIR, SEM and XPS. The findingsprovide theoretical and technical support for the aluminum/wood decorative boardhot-pressing with modified PF.We produced the different composites by modifing PF with other thermoplastic resins aspolyvinyl butyral(PVB) and polyvinyl acetate emulsion (PVAc). The results showed themodified PF with PVAc had better performance whose average value of the surface bondingstrength is1.36MPa. This kind of adhesive was chosen for further study.An orthogonal experiment was designed to examine the mechanical and physical effectson the the composite from the following process parameters: hot-pressing temperature,hot-pressing time, unit pressure and glue content. An analysis of the range and variance of theresults shows that hot-pressing temperature has the largest effect on every quality index of theproduct. The order of relevant factors is hot-pressing temperature> hot-pressing time> unit pressure> glue content. The optimal variables were hot-pressing temperature of140℃,unitpressure of0.6MPa, hot-pressing time of9min and glue content of200g/m2respectively.Surface bonding strength of mixture ratio of PF with PVAc was over1.0MPa. It had thelargest effect on the basis of poplar veneer, but no significant influence on medium densityfiberboard. The optimum mixture ratio of modified PF with PVAc was2:1. The filling ofcoupling agent could improve the surface bonding strength and had the largest effect.The composites could not be ignited. Comparing to MDF, pkHRR, Avg-HRR, EHC andTHR went down by97.3%,98.3%,90.6%and96.6%. But TSR and mass rose by716%and331.9%. The smoke inhibiting property became worse. Release of CO and CO₂was moresteady and lower than MDF.After the aluminium foils were treated with sanding and sanding/watering, its surface freeenergy had been improved by3and5times respectively, as well as a higher wetting. The SEMresults showed that modified PF could wet the aluminum foil surface adequately. Though thecontact rate between aluminum foil and poplar veneer was only about30%, its surfacebonding strength was improved greatly, which showed that the chemical bond had beenformed between aluminum and adhesive.The infrared spectrum analysis showed that the absorption peak was absent on the surfaceof aluminum foils while cured adhesives had the absorption peak of–OH. These above resultsshowed that the chemical bond had been formed between the aluminum and the hydroxyl(–OH) of the adhesives. The absorption peak of carbonyl groups(C=O) had migrated to higherpeak area in PVAc and modified PF with PVAc. As a result, Al-O-C bond was formed.The XPS results showed that Al and Al Oxide existed in the interface and the bindingenergy of C and O migrated to higher area. Meanwhile, many peaks of C1s and O1s indicatedthat the coordination bond between Al and adhesives had been formed.