Luo Jing, Luo Jianlin, Zhang Jizhi, Bai Yuanyuan, Gao Qiang, Li Jianzhang, Li Li
Ministry of Education Key Laboratory of Wooden Material Science and Application, Beijing Key Laboratory of Wood Science and Engineering, College of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China.
School of Materials Science and Engineering, Shandong University, Jinan 250061, China.
Polymers (Basel). 2016 Sep 21;8(9):346. doi: 10.3390/polym8090346.
Soy-based adhesives inherently possess low water resistance and brittleness, which limit their application on plywood fabrication. This investigation involves using a long chain cross-linker, neopentyl glycol diglycidyl ether (NGDE), to produce an intrinsic toughening effect to reduce the brittleness and improve the water resistance of a soybean meal⁻based adhesive. The solids content, viscosity, functional groups, fracture surface micrographs, and thermal stability of the adhesives were measured. Three-layer plywood was fabricated using the resultant adhesive, and the tensile shear strength of the plywood was measured. All adhesive properties were compared with a soybean meal/polyamidoamine-epichlorohydrin (PAE) adhesive and commercial melamine urea formaldehyde resin. The results showed that adding 6 g NGDE improved the water resistance of the soybean meal-based adhesive by 12.5%. This improvement is attributed to the following reasons: (1) a dense cross-linked network is formed by the chemical reaction between NGDE and protein molecules; (2) the toughness of the adhesive increases and a smooth and homogeneous fracture surface is created, which effectively prevents moisture intrusion; (3) the addition of NGDE increases the thermostability of the cured adhesive. The tensile shear strength of the plywood bonded with the soybean meal-based adhesive with 6 g NGDE was 286.2% higher than that without NGDE and attained 1.12 MPa, which was attributed to the reduction in the adhesive's viscosity, and the improvement in the water resistance and toughness of the adhesive. The tensile shear strength of the plywood bonded with 6 g NGDE was 19.1% higher than that with 6 g PAE and was similar to the MUF resin, which validated the novel adhesive being suitable for use as an industrial plywood adhesive.
大豆基胶粘剂天生具有耐水性差和脆性大的特点，这限制了它们在胶合板制造中的应用。本研究涉及使用长链交联剂新戊二醇二缩水甘油醚（NGDE）产生内在增韧效果，以降低脆性并提高豆粕基胶粘剂的耐水性。测量了胶粘剂的固含量、粘度、官能团、断裂表面微观照片和热稳定性。使用所得胶粘剂制造了三层胶合板，并测量了胶合板的拉伸剪切强度。将所有胶粘剂性能与豆粕/聚酰胺多胺-表氯醇（PAE）胶粘剂和商用三聚氰胺脲甲醛树脂进行了比较。结果表明，添加6 g NGDE可使豆粕基胶粘剂的耐水性提高了12.5%。这种改善归因于以下原因：（1）NGDE与蛋白质分子之间的化学反应形成了致密的交联网络；（2）胶粘剂的韧性增加，形成了光滑均匀的断裂表面，有效防止了水分侵入；（3）NGDE的添加提高了固化胶粘剂的热稳定性。与未添加NGDE的豆粕基胶粘剂相比，添加6 g NGDE的胶粘剂所粘结胶合板的拉伸剪切强度提高了286.2%，达到1.12 MPa，这归因于胶粘剂粘度的降低以及耐水性和韧性的提高。添加6 g NGDE的胶粘剂所粘结胶合板的拉伸剪切强度比添加6 g PAE的胶粘剂高19.1%，与三聚氰胺脲甲醛树脂相似，这验证了这种新型胶粘剂适用于工业胶合板胶粘剂。
