Low-Cost and Formaldehyde-Free Wood Adhesive Based on Water-Soluble Olefin-Maleamic Acid Copolymers

Wood-based panels (WBPs) bonded by formaldehyde-based resins, especially urea-formaldehyde (UF) resin, have been recognized as a major source of indoor formaldehyde emission. Although researchers have developed many alternative adhesives to UF resin, their industrial application is limited due to the high cost and complicated gluing process. Here, we report a revolutionary strategy to thoroughly address this challenge. It includes three points: (1) maleic anhydride and olefins with various structures were first alt-copolymerized and then ammoniated to obtain the water-soluble wood adhesive, olefin-maleamic acid (OMA) resin; (2) under high temperatures, especially 180 degree celsius, most of the maleamic acid groups in the OMA resin transform to hydrophobic imide groups, while some of them transform to anhydride groups, which can further cross-link wood by esterification; (3) based on these typical chemical reactions, WBPs can be fabricated under the same hot pressing technology/equipment as UF. Thanks to esterification between wood and OMA resin, plus imidization of amic acid groups, OMA-based WBPs show favorable bonding strength and water resistance even at a low resin content. More importantly, owing to the low cost of cheap olefin feedstocks, the OMA resin will be a promising cost-effective alternative adhesive for the WBP.