Chemical modification of jabon veneers with citric acid–polyol systems: impacts on dimensional stability and bonding performance of plywood

This study elucidated the effects of veneer esterification using citric acid (CA) and CA – polyol systems, namely ethylene glycol-CA (EGCA), glycerol-CA (GlyCA), and sorbitol-CA (SorCA), on the physical and bonding performance of jabon plywood. Veneers were impregnated with 30% modifying solutions, oven-dried at 103°C, and cured at 150°C to induce esterification. Plywood panels were manufactured using UF, MUF, and PF adhesives. Chemical modification was confirmed by the appearance of ester carbonyl signals in the 13C CP/MAS NMR spectra, with increasing esterification intensity in the order CA < EGCA < GlyCA <SorCA. Modified veneers exhibited reduced moisture content and water absorption, indicating enhanced hydrophobicity, while plywood density remained within the typical range for jabon (0.53–0.64 g/cm3). Bonding performance was highly dependent on adhesive type. UF-bonded plywood showed severe delamination, indicating poor compatibility with esterified veneers. In contrast, MUF and PF adhesives provided significantly improved bonding durability, with PF showing the lowest delamination and highest resistance to hydrolytic degradation. CA – polyol modification effectively enhanced the dimensional stability and durability of jabon plywood, particularly when combined with PF adhesive. This approach offers a promising and environmentally friendly strategy for upgrading fast-growing tropical wood for high-performance plywood applications.