Luo Jianlin, Zhang Jieyu, Gao Qiang, Mao An, Li Jianzhang
MOE Key Laboratory of Wooden Material Science and Application, Beijing Key Laboratory of Lignocellulosic Chemistry, MOE Engineering Research Centre of Forestry Biomass Materials and Bioenergy, Beijing Forestry University, Beijing 100083, China.
Collaborative Innovation Center of Sustainable Utilization of Giant Salamander in Guizhou Province, Guizhou Provincial Key Laboratory for Rare Animal and Economic Insects of the Mountainous Region, Guiyang University, Guiyang 550005, China.
Polymers (Basel). 2019 Jul 9;11(7):1167. doi: 10.3390/polym11071167.
The goal of this study is to employ bio-based dialdehyde starch (DAS), derived from in situ polymerization and the resultant microphase separation structure, to improve the strength of melamine-urea-formaldehyde (MUF) resin, as well as enhance the properties that affect its adhesive performance. Thus, we evaluated the effects of DAS on the chemical structure, toughness, curing behavior, thermal stability, and micromorphology of the MUF resin. Furthermore, the wet shear strength and formaldehyde emissions of a manufactured, three-layer plywood were also measured. Results indicate that DAS was chemically introduced into the MUF resin by in situ polymerization between the aldehyde group in the DAS and the amino group and hydroxymethyl group in the resin. Essentially, polymerization caused a DAS soft segment to interpenetrate into the rigid MUF resin cross-linked network, and subsequently form a microphase separation structure. By incorporating 3% DAS into the MUF resin, the elongation at break of impregnated paper increased 48.12%, and the wet shear strength of the plywood increased 23.08%. These improvements were possibly due to one or a combination of the following: (1) DAS polymerization increasing the cross-linking density of the cured system; (2) DAS modification accelerating the curing of the MUF resin; and/or (3) the microphase separation structure, induced by DAS polymerization, improving the cured resin's strength. All the results in this study suggest that the bio-based derivative from in situ polymerization and microphase separation can effectively toughen and enhance the properties that affect adhesive performance in highly cross-linked thermosetting resins.
本研究的目标是利用源自原位聚合及所得微相分离结构的生物基二醛淀粉（DAS），来提高三聚氰胺-尿素-甲醛（MUF）树脂的强度，并增强影响其粘合性能的特性。因此，我们评估了DAS对MUF树脂的化学结构、韧性、固化行为、热稳定性和微观形态的影响。此外，还测量了制成的三层胶合板的湿剪切强度和甲醛释放量。结果表明，通过DAS中的醛基与树脂中的氨基和羟甲基之间的原位聚合，DAS被化学引入到MUF树脂中。从本质上讲，聚合作用使DAS软链段渗透到刚性的MUF树脂交联网络中，并随后形成微相分离结构。通过在MUF树脂中加入3%的DAS，浸渍纸的断裂伸长率提高了48.12%，胶合板的湿剪切强度提高了23.08%。这些改善可能归因于以下一种或多种因素：（1）DAS聚合增加了固化体系的交联密度；（2）DAS改性加速了MUF树脂的固化；和/或（3）DAS聚合诱导的微相分离结构提高了固化树脂的强度。本研究的所有结果表明，原位聚合和微相分离产生的生物基衍生物能够有效地增韧并增强影响高交联热固性树脂粘合性能的特性。
