碱木质素与超支化聚丙烯酸酯乳液复配改性速生青杨的尺寸稳定性研究

【目的】为提升木质素对人工林速生材的尺寸稳定性,本研究提出利用碱木质素与超支化聚丙烯酸酯乳液(HBPA)对速生青杨复合改性的方法。【方法】通过在碱木质素中引入HBPA乳液,配制了质量分数1.31%的碱木质素与质量分数4.00%、8.00%的HBPA乳液的复配乳液(4HL、8HL组),然后分别将碱木质素、HBPA乳液和复配乳液浸渍处理速生青杨,基于改性材的质量增加率、增容率和扫描电镜探究浸渍效果;利用傅里叶变换衰减全反射红外光谱分析HBPA乳液的聚合情况以及改性材化学组分的变化;通过吸水、吸湿性试验对试材的尺寸稳定性进行评价;并对试材的顺纹抗压强度进行测试。【结果】微观上,随着乳液质量分数的增大,固化后黏附在细胞腔内的乳液越多,整体被改性剂填充的导管和木纤维的数量也相应增多。宏观上,随着乳液质量分数的增大,改性材的质量增加率和增容率也相应提高,复配乳液改性材的4HL组质量增加率和增容率分别为8.14%和3.14%,8HL组质量增加率和增容率为15.05%和3.36%,且复配乳液改性材的质量增加率大于碱木质素和HBPA乳液改性材的质量增加率之和;相对于未改性材,复配乳液改性材4HL组和8H...

Dimensional stability of fast-growing Populus cathayana modified with the compound of alkali lignin and hyperbranched polyacrylate emulsion

  Objective  To improve the dimensional stability by lignin on fast-growing wood, this work proposed a compound modification method by alkali lignin and hyperbranched polyacrylate emulsion (HBPA) for fast-growing poplar (Populus cathayana).   Method  By introducing HBPA emulsion into alkali lignin, compound emulsions (group 4HL and 8HL) composed of 1.31% alkali lignin and 4.00% and 8.00% HBPA emulsion were prepared, and then the alkali lignin, HBPA emulsion and their compound emulsions were used separately to treat fast-growing poplar. Mass percentage gain, bulk capacity and scanning electron microscope of the modified wood were used to explore the impregnation effect; the Fourier transform attenuated total reflection infrared spectroscopy was applied to analyze the polymerization of the HBPA emulsion and the composition change of the modified wood; dimensional stability was evaluated through water absorption and moisture adsorption; and longitudinal compressive strength of the samples was tested.   Result  Microscopically, as the concentration of the emulsion increased, more emulsion was observed to adhere to the cell cavity after solidification, and the amount of vessels and wood fibers fully filled with the modifiers increased as well. Macroscopically, with emulsion mass fraction increased, the mass percentage gain and bulk capacity of the modified wood also rose. Specifically, the mass percentage gain and bulk capacity of the 4HL group were 8.14% and 3.14%, and those for the 8HL group were 15.05% and 3.36%, respectively, and the mass percentage gain of the compound emulsion modified samples was greater than that of the sum for alkali lignin and HBPA emulsion individual treatment. Compared with the alkali lignin, unmodified wood, water absorption rate at 192 h for the 4HL and 8HL groups of the compound emulsion modified wood reduced by 29.4% and 35.3%, and the corresponding volume swelling rate decreased by 28.5% and 29.7%, respectively. After 21 d of moisture adsorption under 84% relative humidity, moisture content reduced by 6.9% and 11.5%, and the corresponding volume swelling rate decreased by 21.3% and 26.0%, respectively. HBPA emulsion and compound emulsion effectively enhanced the longitudinal compressive strength of treated wood, but this change trend was not related to the mass fraction of HBPA emulsion.   Conclusion  Compared with alkali lignin and HBPA emulsion modified wood, the mass percentage gain and bulk capacity of the compound emulsion modified wood were higher, the water absorption and moisture adsorption decreased significantly, and the dimensional stability was promoted greatly, confirming the compound modification effect of lignin and HBPA emulsion on fast-growing poplar.