基于多酚-铁络合的白橡单板表面颜色调控

Surface color regulation of white oak veneers based on polyphenol-iron complexation

白橡木由于材质坚硬和纹理清晰等特点,在木地板制造行业应用广泛,然而白橡单板在生产过程中存在色差大且颜色稳定性差等缺点。为获得颜色均匀且稳定的深色白橡单板,采用超声波辅助乙醇法提取白橡多酚,并用福林酚比色法、显色反应鉴定、液质联用测试(LC-MS)确定白橡多酚含量及单体类型;采用质量分数为0.01%,0.03%,0.05%,0.08%,0.10%5种低质量分数的硫酸亚铁溶液,对白橡单板进行浸渍处理,通过铁络合实现了颜色调控;利用氙灯老化试验法探究了络合处理对白橡单板耐光色牢度的影响;通过X射线光电子能谱仪(XPS)和紫外-可见-近红外光分光光度计(UV-vis)分析了多酚-铁络合及老化机理。结果表明:随着硫酸亚铁质量分数的提高,白橡单板由淡黄色向灰色、蓝黑色和黑色依次转变;白橡单板间色差从络合处理前的3.7降低到0.2;经96 h氙灯老化试验后,白橡单板的耐光色牢度提高,木材表面仍保留清晰纹理。紫外漫反射光谱和XPS检测结果表明,白橡多酚与铁的络合消耗了大量酚类物质,在形成络合物的过程中发生π轨道跃迁,经紫外线老化后,单板内木质素和多酚类物质发生光降解生成醌类物质,Fe^(2+)大部分被氧化成Fe^(3+),使络合单板表面颜色更暗、更红、更黄。使用低质量分数的硫酸亚铁溶液对白橡单板浸渍处理可以实现白橡单板的表面颜色调控,增强单板的纹理层次感,降低单板间色差,提高单板的耐光色牢度。

In recent years,with people's pursuit of environmental protection and personalized products and the rise of cool color decoration style,the low-carbon,environmental and green polyphenol-iron wood color regulation technology has attracted great attention.White oak veneers have a wide use in the wood floor manufacturing industry because they are a hard material with clear and beautiful texture.However,white oak veneers have drawbacks of large color difference and poor color stability in the production process.In order to obtain uniform and stable dark white oak floors,in this study,the ultrasonic assisted ethanol was used to the extraction of white oak polyphenols and its content and monomer types was analyzed by the Foline-phenol colorimetry,chromogenic reaction and liquid chromatography-mass spectrometry(LC-MS).Meanwhile,the low mass ratio of ferrous sulfate(0.01%,0.03%,0.05%,0.08%,or 0.10%)was used to impregnate white oak veneers using polyphenols in white oak veneers.The color regulation was realized by in-situ complexation of polyphenols in the white oak with the ferrous sulfate.The xenon lamp aging test was used to investigate the influence of complexation treatment on the color fastness to UV-light of white oak veneers.Finally,the X-ray photoelectron spectrometer(XPS)and ultraviolet-visible-near-infrared spectrophotometer(UV-vis)were applied to analyze the mechanisms of complexation and aging of polyphenol-iron.The results showed that the faint yellow white oak veneers changed into black and blue with the increase of the Fe(Ⅱ)mass ratio.The color difference between veneers decreased from 3.7 to 0.2.After 96 h of the xenon lamp aging test,the color fastness to UV-light was higher than that of the untreated veneers.The UV diffuse reflection spectrum and XPS detection results indicated that the complexation of white oak polyphenols with iron consumed large amount of phenol and the π orbital transition occurred during the formation of the complex.After the UV aging,lignin and polyphenols in the veneers were photodegraded to produce quinones with most of the Fe^(2+)oxidized to Fe^(3+),which made the surface color of the complexed veneers darker,redder,and more yellow.The in-situ impregnated complexation of white oak veneers with low mass ratio of ferrous sulfate solution could not only regulate the wood color,enhancing the wood texture and reducing the color difference,but also enhance the color fastness to UV-light.