Synthesis, performance and structure characterization of glyoxal-monomethylolurea-melamine (G-MMU-M) co-condensed resin

In order to reduce the formaldehyde emission of formaldehyde-based wood adhesive from the source, it is aimed to develop a novel co-condensed resin of glyoxal-monomethylolurea-melamine (G-MMU-M). A series of G-MMU-M resins with various formulations of raw materials were successfully prepared. The basic properties and bonding performance of the G-MMU-M resins were determined. Furthermore, the structures of resins were characterized by FTIR, 13C NMR, XPS, and ESI-MS. The results show that the prepared G-MMU-M resin remains stable for 30 d, meanwhile, the dry and wet bonding strength of the plywoods bonded with the resins, solid content and viscosity are influenced greatly by the addition amount of melamine and MMU/G molar ratio. The G-MMU-M resins with MMU/G molar ratio of 0.9:1.0 and 8% melamine exhibit the highest dry and bonding strength of 1.98 MPa and 1.27 MPa, increased by 34% and 63%, respectively, in comparison with glyoxal-monomethylolurea (G-MMU) resin. In the G-MMU-M resins, there were four main oligomers including M-CH(-'CH-MMU)-O-MMU, M-CH(- CH2OH)-MMU-O-MMU, M-CH(-OH)-'CH-MMU-O-MMU, and M-CH(-'CH-MMU)-MMU-p-G.(C) 2022 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

Automated summary

To reduce formaldehyde emissions from formaldehyde-based wood adhesive, a novel co-condensed resin of glyoxal-monomethylolurea-melamine (G-MMU-M) was developed. Various formulations of G-MMU-M resins were prepared and their properties and bonding performance were determined. The structures of the resins were characterized using FTIR, 13C NMR, XPS, and ESI-MS. The results showed that the G-MMU-M resins remained stable for 30 days and the bonding strength of plywoods bonded with the resins was influenced by the addition amount of melamine and the MMU/G molar ratio.