蔗糖/DMDHEU改性对木材涂饰和 老化性能的影响

以改性杨木和辐射松及其对照材为研究对象,采用3种水性涂料分别对其进行涂饰处理,系统地研究了蔗糖/DMDHEU改性处理对响叶杨和辐射松木材涂饰和老化性能的影响规律。结果显示,与未处理木材相比,改性木材表面的水接触角稍微降低,漆膜附着力显著提高,这有助于增强水性涂料在木材表面的润湿性和耐久性。由于改性剂中含有大量未反应的自由羟基,因而导致漆膜在改性木材表面的干燥速度有所降低。经过12个月室外老化测试,改性木材表面颜色变化ΔE*较未处理木材小,改性木材表面产生的开裂比未改性木材少且小。红外光谱分析显示,所有老化木材表面的木质素典型特征峰均消失,表明该改性处理并不能实质性防止木材表面木质素的光降解。
Fast-growing wood species are important raw materials for Chinese wood industry. However, they usually have drawbacks of soft, low density, and easy deformation during their utilization. Chemical modification is one of the strategies to improve their quality. The modification process may thus result in positive or negative effects on the wood coating performance. In this study, we measured the coating and weathering performance of the Populus adenopoda and Pinus radiata wood modified with the aqueous mixture of sucrose and 1,3-dimethylol-4,5-dihydroxyethyleneurea(DMDHEU). The results showed that, compared to the untreated wood, the modified wood surface exhibited a slightly lower water contact angle and an obvious increase in finish wet adhesion, which facilitated to enhance the wettability of finishes on the wood surface and durability during service. Because of the presence of excessive non-reactive hydroxyl groups in modifying agents incorporated in wood, the drying time of finishes on the wood increased due to ease of forming hydrogen bonds between chemical and water in finishes. After 12 months outdoor weathering, the modification reduced ΔE* compared to the unmodified wood. The uncoated wood surfaces presented visual tiny checks and cracks after 9 months weathering, but the number of checks on the modified wood was less than that on the unmodified controls. The results of FTIR spectral analysis indicated that the characteristic peaks assigned to lignin for the untreated and treated wood disappeared after the weathering, suggesting that the modification with sucrose/DMDHEU cannot substantially prevent wood lignin from photo-degradation during outdoor exposure