辊压树脂浸胶法对桉木重组木尺寸稳定性影响机理

Influence mechanism of roller-press impregnation on the dimensional stability of eucalyptus scrimber

【目的】为解决重组木制备过程中重组单元施胶不均匀导致的尺寸稳定性差的问题,通过辊压树脂浸胶工艺制备重组木,探究辊压树脂浸胶工艺对桉木重组木尺寸稳定性的影响机理。【方法】分别通过吊笼式浸胶法和辊压树脂浸胶法制备桉木重组木,采用超景深显微镜、扫描电子显微镜、微计算机断层扫描仪和激光共聚焦显微镜观察重组单元和重组木表面形貌、微观结构和胶液分布情况,并采用X射线光电子能谱仪、粗糙度仪、接触角测定仪以及63℃水泡24 h和28 h循环法(沸水煮4 h,63℃烘20 h,沸水煮4 h)研究重组木表面化学成分、表面粗糙度、表面润湿性和耐水性能。【结果】与吊笼式浸胶法制备的重组木(CWS)相比,辊压树脂浸胶法制备的重组木(RWS)表面裂隙减少,粗糙度降低,表面润湿性减弱,耐水性能显著增强。RWS表面粗糙度R_(a)和R_(z)相比CWS分别下降了34.38%和72.75%。接触角测试结果表明,第20 s时RWS的表面接触角相对于CWS增大幅度为283.95%。63℃水泡24 h测试结果显示:RWS的吸水厚度膨胀率和吸水宽度膨胀率分别为5.47%和1.11%,与CWS相比降低幅度分别达到52.16%和50.09%。28 h循环测试结果显示:RWS的吸水厚度膨胀率和吸水宽度膨胀率分别为6.24%和1.17%,与CWS相比降低幅度分别为51.45%和58.51%。辊压浸胶过程对重组单元产生了二次破坏,增加了胶液进入的通道;同时,辊压使细胞在被压缩到恢复原貌的过程中产生的负压,增加了胶液的渗透深度,形成网状胶合结构,加强了重组木的胶合性能,抑制了木材细胞在吸水后的回弹。【结论】辊压树脂浸胶法提高了重组木内部胶液分布的均匀性,降低了桉木重组木表面的粗糙度和润湿性,显著提高了重组木的耐水性能,改善了重组木的尺寸稳定性,对重组木的工艺优化和连续化生产具有重要的参考和指导意义。

[Objective]To solve the problem of poor dimensional stability caused by the uneven disintegration during the preparation process of scrimber,the scrimber was prepared by roller-press impregnation,and the influence mechanism of roller-press impregnation on the dimensional stability of eucalyptus scrimber was explored.[Method]In this study,eucalyptus scrimber was prepared by cage and roller-press impregnation techniques,and the surface morphology,microstructure,and glue distribution were observed by ultra-depth microscope,scanning electron microscope,microcomputer tomography scanner,and laser confocal microscope.The surface chemical composition,surface roughness,surface wettability,and water resistance of scrimber were studied by X-ray photoelectron spectroscopy,roughness tester,contact angle tester,soaking at 63℃for 24 h,and 28 h cycle treatment(boiling for 4 h,dry at 63℃for 20 h,boiling for 4 h).[Result]Compared with the wood scrimber prepared by cage impregnation(CWS),the surface cracks,roughness,and the surface wettability of wood scrimber prepared by roller-press impregnation(RWS)were reduced,and the water resistance of RWS was significantly increased.The results of roughness showed that compared with CWS,the surface roughness R_(a) and R_(z) of RWS decreased by 34.38%and 72.75%,respectively.The contact angle test results indicated that the surface wettability of RWS was weakened,and the surface contact angle of RWS increased by 283.95%compared with CWS at the 20th second.The test result of soaking at 63℃for 24 h showed that the thickness swelling ratio(TSR)and width swelling ratio(WSR)of RWS were 5.47%and 1.11%,respectively,which were 52.16%and 50.09%lower than those of CWS.The TSR and WSR of RWS under 28 h cycle treatment were 6.24%and 1.17%,respectively,which were reduced by 51.45%and 58.51%,respectively.The process of roller press caused secondary damage to the recombination unit,which increased the flow path for PF resin solution.At the same time,the negative pressure generated by the roller pressing during the process from compressing the cells to restoring their original appearance increased the penetration depth of the glue,formed a network bonding structure,strengthened the bonding performance of the recombined wood,and inhibited the rebound of wood cells after water absorption.[Conclusion]The roller-press impregnation improves the uniformity of glue distribution in scrimber,reduces the surface roughness of eucalyptus scrimber and wettability,and significantly improves the water resistance and dimensional stability,which has important references and guidance for the process optimization and continuous production of scrimber.