等离子体改性热塑性树脂薄膜制备环保胶合板试验

为获得无甲醛释放的环保胶合板,将热塑性树脂薄膜(低密度聚乙烯(LLDPE)、聚丙烯(PP)、聚氯乙烯(PVC))用作胶黏剂,并利用空气介质阻挡等离子体对热塑性树脂薄膜进行表面改性处理以提高薄膜与杨木单板的界面相容性,从而获得性能良好的环保胶合板。研究了等离子体处理对胶合板胶合性能的影响,并从等离子体处理对热塑性树脂薄膜表面化学组分及其对胶合板界面形貌的影响分析其胶合机理。结果表明:在等离子体处理功率为4.5 kW、处理时间为8 m/min的条件下处理热塑性树脂薄膜,胶合板的胶合强度得到显著提高,LLDPE/杨木胶合板的胶合强度从0.49 MPa增至0.81 MPa,PP/杨木胶合板的胶合强度从0.65 MPa提高到0.84 MPa,均达到Ⅱ类胶合板标准要求。其中用等离子体处理后PVC与杨木制备的胶合板能满足Ⅰ类胶合板的标准要求,胶合强度达到0.79 MPa。XPS分析表明,等离子体改性热塑性树脂薄膜的表面发生了氧化反应,引入了含氧官能团,提高了薄膜表面极性,有利于提高薄膜与杨木单板之间的相互作用,从而使得胶合板的界面胶合更为紧密,说明等离子体处理后树脂与杨木单板的相容性提高,树脂能在单板表面更好地附着。热塑性树脂薄膜与杨木单板制备的胶合板仅有极微量甲醛释放,其主要源于木材自身,远低于国家标准对人造板甲醛释放限量的要求。研究证明等离子体处理能明显改善热塑性树脂薄膜与杨木单板的界面相容性。

Plasma-treated thermoplastic resin film as adhesive for preparing environmentally-friendly plywood

Since plywood is the main material in indoor decoration,its environmental protection,especially the emission of formaldehyde,has become the focus of people s attention.To solve the problem of formaldehyde release in wood-based panels,the thermoplastic resins have received more and more attention due to its excellent performance and free formaldehyde emission.In this study,thermoplastic resins(low density linear polyethylene,polypropylene and polyvinyl chloride)were used as adhesive to produce plywood for indoor applications.To overcome the nonpolar surface of thermoplastic resin and improve the interfacial bonding between resin and wood,the dielectric barrier discharge(DBD)plasma was applied to promote polarity of film and improve the bonding strength between the wood and resin adhesive.The process of the DBD treatment did not need additional chemical substances and produce any harmful substances,and it only affected the surface of the material.The whole process was efficient and environmentally friendly.The DBD plasma was used to treat resin to improve the interface compatibility between resin and poplar veneer in this study.The effect of plasma treatment on the bonding properties of plywood was studied,and the chemical composition of thermoplastic resins and the interface structure of plywood were characterized by the X-ray photoelectron spectroscopy(XPS)and scanning electronic microscopy(SEM),respectively.The obtained results showed that the resin surface was evidently oxidized and multiple oxygen-containing functional groups were grafted on the thermoplastic resin surface after the plasma treatment of 4.5 kW and 8 m/min,which was beneficial to the adhesion of resins on the wood surface.After the plasma treatment,the bonding strength of the LLDPE plywood increased from 0.49 MPa to 0.81 MPa and the bonding strength of PP plywood increased to 0.84 MPa,which met the bonding performance requirements of type II plywood,even the PVC plywood could meet the standard requirements ofⅠplywood(up to 0.79 MPa).The formaldehyde emission of plywood was far lower than the national standard value,and the formaldehyde mainly came from the wood.It could be concluded that the DBD plasma treatment could improve the bonding strength between wood and thermoplastic resin adhesives and the plasma-treated thermoplastic resins could be used as wood adhesives to produce environment-friendly plywood.