木质纤维的冷冻活化及其制备无胶板材

Freezing Activation of Wood Fibers and Preparation of Binder-free Boards

利用氢氧化钠-聚乙二醇-尿素混合溶液对木质纤维进行冷冻活化处理,然后制备无胶纤维板,通过对比无胶胶合纤维板力学性能,确定木质纤维较佳冷冻活化工艺,并利用傅里叶变换红外光谱、X射线衍射分析、差式扫描量热分析、热重分析、X射线光电子能谱分析对木质纤维的冷冻活化效果进行表征。研究结果表明:木质纤维较佳冷冻活化工艺为氢氧化钠、聚乙二醇、尿素的质量比7∶4.2∶12,活化剂质量(以氢氧化钠与尿素的总质量计)与木质纤维的质量比1∶12,冷冻温度-15℃,冷冻时间45 min;以此工艺活化处理的木质纤维为原料,所制备纤维板的吸水厚度膨胀率、内结合强度、静曲强度、弹性模量分别优于GB/T 11718—2009《中密度纤维板》性能要求(各指标数值分别提升了45%、238%、177%和129%);冷冻活化处理会破坏木质纤维中纤维素间的氢键,提高羟基的反应活性并增加活性羟基的数量,在扩张纤维素晶格的同时产生新的结晶并且降低木质纤维的热稳定性。

Sodium hydroxide-polyethylene glycol-urea mixed solution was used to activate wood fiber under freezing, and then the binder-free fiberboard was prepared. By comparing the mechanical properties of binder-free bonding fiberboard, the better freezing activation process of eucalyptus fiber was determined. The freezing activation effect of wood fiber was characterized by FT-IR, XRD, DSC, TG and XPS. The results showed that the better freezing conditions were as follows: the mass ratio of sodium hydroxide, polyethylene glycol, and urea was 7 ∶4.2 ∶12, the mass ratio of activator(i.e, the total mass of sodium hydroxide and urea) and wood fiber was 1 ∶12, the freezing temperature was-15 ℃ and the freezing time was 45 min. The water absorption thickness expansion rate, internal bonding strength, static bending strength, and elastic modulus of the prepared fiberboard increased by 45%, 238%, 177%, and 129% of the performance requirements in GB/T 11718-2009 Medium Density Fiberboard, respectively. The freezing activation treatment could destroy the hydrogen bond between the cellulose in the wood fiber, improve the reaction activity of hydroxyl and increase the number of active hydroxyl, produce new crystals while expanding the cellulose lattice, and reduce the thermal stability of the wood fiber.