A bio-based route to formaldehyde-free, wet-durable wood bonding: aldehyde-functionalized straw microparticles stabilize networks and interphases in polyacrylamide adhesives

Abstract

Polyacrylamide (PAM) can offer strong dry wood adhesion via amide-wood hydrogen bonding but typically fails in water due to severe network swelling. Here we report a reinforcing approach using aldehyde-functionalized straw microparticles (AFstraw) as a multifunctional reactive lignocellulosic component. AFstraw was prepared via periodate-mediated aldehydation and dispersed into an aqueous bio-synthesized acrylamide (bio-AM) precursor before curing. Compared with neat PAM that shows no measurable wet strength, PAM/AFstraw enables a step-change in wet durability while preserving excellent dry bonding. Optimal processing formulation delivers up to 1.73 MPa wet strength after 63 °C water soaking, well above the commonly referenced 0.7 MPa criterion. Microscopy collectively reveals a more adhesive-rich bondline, consistent with stabilization of the wood-adhesive interphase. FTIR indicates aldehyde consumption, while swelling tests support adhesive-network stabilization in water (31% vs. 530% for neat PAM). A cradle-to-gate LCA indicates a low GWP (2.44 kg CO2-eq kg-1 adhesive) and lower modeled toxicity-related potentials relative to several mainstream resins, while identifying sodium periodate and electricity as dominant hotspots. Overall, this work demonstrates an aldehyde-enabled strategy that uses lignocellulosic microparticles to unlock PAM’s adhesive potential, opening possibilities toward sustainable wood composite manufacturing.