Modular assembly of TA-Fe3+ functionalized PVAc/PS emulsion particles with SiO2 particles: Enhancing the bond strength of waterborne wood adhesives

Improving the bond strength of wood emulsion adhesives is an ongoing challenge for the wood-processing industry. In this study, PVAc/PS core-shell emulsion particles are functionalized by forming coordination complexes between natural biomaterial tannic acid (TA) and Fe 3+ . The functionalized emulsion particles are assembled on the surface of the core template SiO 2 to form a “superstructure” through hydrogen bonding between the phenolic hydroxyl groups in the TA and the hydroxyl groups on the surface of SiO 2 , which can enhance the cohesive strength of the emulsion adhesive layer, thereby increasing the peel strength of wood adhesives. The results indicated that the functionalized emulsion particles were most effectively assembled on core template SiO 2 particles when the ratio of TA to Fe 3+ was 1:1 and the encapsulation rate of the assembled SiO 2 particles was 150 %. The glass transition temperatures (Tg1 and Tg2), storage modulus, tensile strength, and hardness of the assembled PVAc/PS emulsion film were measured by DSC, DMA, tensile testing machine, and durometer. These properties increased by 11.6 %, 5.3 %, 14.9 %, 127.6 %, and 46.3 %, respectively, compared to those of the PVAc/PS emulsion film. Further, the shear strength of the assembled PVAc/PS emulsion for bonding wood blocks and the peel strength for bonding thin veneers increased by 33.8 and 35.7 %, respectively, compared to those of the PVAc/PS emulsion. This study confirmed that using a modular assembly to improve PVAc/PS emulsion bonding properties can help formulate high-performance waterborne emulsion adhesives with promising applications in the field of thin-wood veneer bonding. This strategy provides an effective method to design and build environmentally friendly, low-cost, and high-performance water-based emulsion adhesives.