TY  - EJOU
AU  - Anggini, Awanda Wira 
AU  - Sari, Rita Kartika 
AU  - Mardawati, Efri 
AU  - Karliati, Tati 
AU  - Iswanto, Apri Heri 
AU  - Lubis, Muhammad Adly Rahandi 

TI  - Overview of the Synthesis, Characterization, and Application of Tannin-Glyoxal Adhesive for Wood-Based Composites
T2  - Journal of Renewable Materials

PY  - 2024
VL  - 12
IS  - 7
SN  - 2164-6341

AB  - More than a century after its initial synthesis, urea-formaldehyde (UF) resins still have dominant applications as adhesives, paints, and coatings. However, formaldehyde in this industry produces formaldehyde emissions that are dangerous to health. Scientists have spent the last decade replacing formaldehyde and phenol with environmentally friendly substances such as glyoxal and tannin to create bio-based adhesives. This review covers recent advances in synthesizing glyoxal tannin-based resins, especially those made from sustainable raw material substitutes and changes made to synthetic processes to improve mechanical properties. The efficacy of using tannin-glyoxal adhesives in producing wood-based composites has been proven. The glyoxylate reaction forms cross-linked bridges between the aromatic sites of the tannin and glyoxal molecular structures. Glyoxal tannin adhesive with a greater percentage of glyoxal than tannin will produce an adhesive with better characteristics. The gel time reduces as the hardener concentration rises from 7.5% to 15% when glyoxal is used in adhesives. However, excessive amounts of glyoxal will result in a decrease in viscosity values. Glyoxal exhibits faster delivery degradation when it reaches a maximum temperature of approximately 130°C, although it initiates the curing process slightly slower at 110°C. Adding glyoxal to tannin-based adhesives can improve the mechanical properties of composite boards. The wet shear strength of the resulting plywood is increased by 105.4% with the addition of 5-weight percent tannin-based resin with glyoxal as a cross-linker in Soy Protein Adhesive. With glyoxal as a hardener, the panels produced showed good internal bond strengths (>0.35 MPa) and met the international standard specifications for interior-grade panels.
KW  - Bio-based adhesives; glyoxal; tannin; wood adhesives; wood-based composites

DO  - 10.32604/jrm.2024.051854