A Green Resin Wood Adhesive from Synthetic Polyamide Crosslinking with Glyoxal

Abstract

Glyoxal is considered to be the most likely substitute for formaldehyde to synthesize resin adhesives for wood bonding due to its reactivity, structural characteristics, being non-toxic, low volatility, and acceptable cost. Regrettably, the performance of the resin synthesized using glyoxal to directly replace all formaldehyde is not totally satisfactory, especially as it has almost no water resistance. This makes such a simple alternative fail to be suitable for industrial production. To prepare an environment-friendly glyoxal-based adhesive with good bonding performance, the work presented here relies first on reacting citric acid and hexamethylene diamine, producing a polyamide, with glyoxal, and then crosslinking it, thus synthesizing a thermosetting resin (namely CHG) adhesive and applying it for plywood bonding. The plywood prepared exhibits excellent dry and wet shear strength, which are better than GB/T9846-2015 standard requirements (≥0.7 MPa), and even after being soaked in hot water at 63 °C for 3 h, its strength is still as high as 1.35 MPa. The CHG resin is then potentially an adhesive for industrial application for replacing UF (urea-formaldehyde) and MUF (melamine-urea-formaldehyde) adhesives for wood composites.

Long-Chain Polyamine-Glyoxal Wood Adhesive: Formaldehyde-Free, Green Synthesis, and Ultra-Performances

“…Further, MHG resins are also unique because they are highly resistant to boiling water as boiling water soaking bonding strength has never been reported for other glyoxal-related adhesives. According to the results in the literature, − ,,,,− only dry bonding strengths of plywood were reported for pure MG and UG, and a few studies reported cold water soaking bonding strengths. ,,− As for other composite adhesives, to make them more stable toward hydrolysis, more components were used with glyoxal, such as oxidized cassava starch and polyethyleneimine (PEI), leading to, namely, UG-oxidized cassava starch (UGCS) and polyethyleneimine-UG (HBPEIUG) adhesives. Note that PEI is also a branched polyamine containing terminal amino groups.…”

Metabolic Engineering of Microorganisms Towards the Biomanufacturing of Non-Natural C5 and C6 Chemicals

“…HMDA, also named 1,6-hexanediamine or 1,6-diaminohexane, serves as a precursor for the production of nylon-6,6 and various resins [44,120]. Beyond its application in nylon production, HMDA is also utilized in the textile and water treatment industries [120]. So far, some whole-cell bioconversion approaches were reported for its production.…”

Self‐healing efficiency of cinnamaldehyde‐crosslinked soy protein resins with elongated soy protein microcapsules

“…Many commercial aldehyde crosslinkers, including glyoxal, glutaraldehyde, and formaldehyde, have been studied and commonly applied in wood-based composite materials and resins to enhance their strength and water resistance. [20][21][22][23][24] Chabba and Netravali found that crosslinking soy protein concentrate-based (SPC) resins with 10% (w/w) glutaraldehyde increased the fracture stress and Young's modulus by 20% and 35%, respectively, along with improvement in moisture resistance. 25 When modified with 5% (w/w) formaldehyde, SPI films significantly increased tensile strength by about 20% and Young's modulus by 15%.…”

“…Nonetheless, researchers have successfully crosslinked soy protein‐based resins, using external crosslinkers, to enhance their mechanical and thermal properties while minimizing moisture absorption. Many commercial aldehyde crosslinkers, including glyoxal, glutaraldehyde, and formaldehyde, have been studied and commonly applied in wood‐based composite materials and resins to enhance their strength and water resistance 20–24 . Chabba and Netravali found that crosslinking soy protein concentrate‐based (SPC) resins with 10% (w/w) glutaraldehyde increased the fracture stress and Young's modulus by 20% and 35%, respectively, along with improvement in moisture resistance 25 .…”