桐油处理对木材摩擦焊接界面的保护机理

Characterization of Protection Mechanism of Wood Friction Welding Interface by Tung Oil Treatment

木材摩擦焊接是一种不使用胶水或其他黏合剂连接木材或几个木材部件或人造板的新工艺。本文为提高木材摩擦焊接技术耐水性,以木荷榫和榉木块为研究对象,设置A到E组分别为:桐油蒸煮木榫10、20、30 min、桐油直接涂覆、无处理,F组先焊接后涂覆桐油。处理过的试件焊接后分别测量其在3种环境下的焊接干强度、湿强度和烘干强度,研究桐油处理对焊接界面性能和耐水性提高的机理。结果表明:A组的干强度与湿强度优于除F组的其他各组,说明桐油蒸煮能够有效提高焊接界面的性能。而F组3种抗拉强度均优于其他各组,其干强度、湿强度与烘干强度分别比E组高73.4%、5.3%、12.0%。FTIR、XRD、XPS分析揭示,焊接前进行短时间桐油蒸煮能够使桐油浸入预焊接表面,焊接过程中会减少半纤维素与纤维素的过度分解,促进焊接过程中木材组分的解聚、热解形成熔融物质,润滑了焊接界面表面的同时避免了焊接层过度碳化;而焊接后对试件进行桐油涂覆,一方面桐油能够在试件表面形成油膜,避免焊接表面在浸泡时渗入水分子,保护焊接界面,另一方面少量桐油会渗入焊接表面并与碳化后的木材组分混合,增大木荷榫和榉木块之间的摩擦力。

Wood friction welding is a new technology that does not use glue or other adhesives to connect wood or several wood parts or wood-based panels.To improve the water resistance of wood friction welding technology,this paper took the tenon of Schima superba wood and Zelkova serrata wood block as the research materials,which were subject to different treatment methods:boiling the wood tenon in tung oil for 10(A),20(B),30(C)min,direct tung oil coating(D),no treatment(E),welding first and then coated with tung oil(F).The tensile strength of the treated specimens after welding was measured in three environments,which were recorded as welding dry strength,wet strength and drying strength.At the same time,the mechanisms of tung oil treatment on the improvements of welding interface performance and water-resistance were studied.The results showed that the dry strength and wet strength of group A were better than those of other groups except for group F,indicating that tung oil boiling can effectively improve the performance of the welding interface.The dry strength,wet strength and dried strength of group F were 73.4%,5.3%,and 12.0%higher than those of group E,respectively.FTIR,XRD,XPS analysis results revealed the protection mechanism of tung oil on the welding interface:a short time of tung oil boiling before welding can make tung oil penetrate into the pre-welded surface.During the welding process,tung oil will reduce the excessive decomposition of hemicellulose and cellulose,promote the depolymerization and pyrolysis of wood components during the welding process to form molten substances,lubricate the surface of the welding interface and avoid excessive carbonization of the welding layer.Coating tung oil on the specimen after welding,on the one hand,can make the tung oil form an oil film on the surface of the specimen,avoid the infiltration of water molecules on the welding surface during immersion,and protect the welding interface.On the other hand,a small amount of tung oil will penetrate the welding surface and mix with the carbonized wood components to increase the friction between the wood tenon and the beech block.