三聚氰胺-尿素-乙二醛共缩聚树脂的固化性能及结构分析

Curing properties and structure analysis of melamine-urea-glyoxal co-condensed resin

为降低木质人造板产生的游离甲醛对人体健康和环境造成的危害,本论文采用低毒且常温下不挥发的乙二醛(G)与三聚氰胺(M)和尿素(U)进行反应,制备三聚氰胺-尿素-乙二醛(MUG)共缩聚树脂。采用动态热力分析(DMA)方法研究了原料摩尔比、反应pH、反应温度、反应时间对MUG树脂固化性能的影响;采用^(13)C-NMR和XPS等分析手段对树脂结构进行表征;并以不同原料摩尔比的MUG树脂制备胶合板并测定其物理力学性能。结果表明:MUG树脂稳定性较好,常温下外观为金黄色透明液体;树脂的固含量及黏度受原料摩尔比的影响较大,均随着M添加量的增多而增大;^(13)C-NMR和XPS分析证明了体系中M、U、G三者之间的共缩聚反应。当原料摩尔比R=n(M)∶n(U)∶n(G)=0.^(13)∶0.30∶1.0、反应温度70℃、反应pH为5.0~6.0、反应时间50 min时,所合成树脂具有较低的固化温度和较高的储能模量,所制得胶合板的干状剪切强度、冷水24h湿强度和热水3h湿强度均较好,分别为2.11MPa、1.24MPa和0.75MPa。

In order to reduce the harm of free formaldehyde produced by wood-based panel to human health and environment,this paper chose low-toxic and low-volatile glyoxal(G)to react with melamine(M)and urea(U)to prepare melamine-urea-glyoxal(MUG)co-condensed resins.The effects of molar ratio of raw materials,reaction pH,reaction temperature and reaction time on the curing properties of the synthesized MUG resin were studied by dynamic thermo-mechanical analysis(DMA).The resin structure was characterized by nuclear magnetic resonance carbon spectroscopy(^(13)C-NMR)and X-ray photoelectron spectroscopy(XPS),the physical and mechanical properties of plywood bonded with the MUG resins with different molar ratios of raw materials were determined.The results showed that the resins prepared under different conditions were stable and golden yellow transparent liquid at room temperature.The solid content and viscosity of the resins were greatly affected by the molar ratio of raw materials,and both increased with the addition amount of melamine.The results obtained by^(13)C-NMR and XPS proved that the co-polycondensation reaction among M,U and G does exist in the system.When R=0.^(13):0.30:1.0,the reaction temperature of 70℃,the reaction pH of 5.0~6.0,and the reaction time of 50 min,the curing temperature of the resin is lower,the energy storage modulus is higher,the dry shear strength of the plywood,the wet strength of cold water for 24h and of hot water for 3h are better,which are 2.11MPa,1.24MPa and 0.75MPa,respectively.