环氧化木质素增强三聚氰胺-尿素-甲醛共缩聚树脂研究

Investigation on the Epoxidized Lignin for Reinforcing Melamine-Urea-Formaldehyde Co-condensation Resins

利用环氧氯丙烷与木质素分子中的羟基和羧基环氧化反应制备环氧化木质素(EL),并将EL用作三聚氰胺-尿素-甲醛共缩聚树脂(MUF)的无醛交联剂,提高树脂胶合强度,同时EL与MUF树脂中的游离甲醛反应,有助于降低树脂的甲醛释放量。采用红外光谱和化学滴定法分析发现:随着木质素与环氧氯丙烷开环反应温度升高,EL环氧基团含量呈先增多后减少的趋势,开环温度100℃时制得的EL(EL-100)环氧指数达到最高为2.6 mol/kg。与未添加EL的MUF树脂相比,添加5%EL-100的MUF树脂固化后的弹性模量(5.94 MPa)提高了117%,胶合强度(1.11 MPa)提高了33.7%,甲醛释放量(0.206 mg/L)降低了27.0%。

Epoxidized lignin(EL)was prepared by epoxidation of epichlorohydrin with the hydroxyl and carboxyl groups in lignin molecules.EL was used as a formaldehyde-free cross-linking agent for melamine-urea-formaldehyde(MUF)co-condensation resins to improve the bonding strength of MUF resin,and the reaction between EL and free formaldehyde in the MUF resin decreased the formaldehyde emissions of resin.With the increase of ring-opening reaction temperature between lignin and epichlorohydrin,the epoxy group content of EL showed a trend of increasing and then decreasing,which was determined by the infrared spectroscopy and chemical titration methods.The EL epoxy index reached the highest value of 2.6 mol/kg at 100℃.Compared with the MUF resin without EL,the modulus of elasticity(5.94 MPa)of added 5%EL-100 MUF resin increased by 117%after curing,and shear strength(1.11 MPa)increased by 33.7%and the formaldehyde emission(0.206 mg/L)decreased by 27.0%.