Hydroxyl-functional acrylic adhesives: leveraging polysilazane chemistry for curing†

Acrylic-based wood adhesives are widely recognized for their durability, UV resistance, and rapid drying properties, traditionally achieved using isocyanate-based curing systems despite their inherent toxicity. In this study, the potential of polysilazane (PSZ) as an alternative cross-linker for functional acrylic polymers was evaluated, focusing on adhesive properties. The crosslinking interactions between the acrylic polymer and PSZ formed a highly stable Si–O reinforced three-dimensional network, as characterized by analytical techniques and further supported by enhanced thermal stability and adhesive performance. The PSZ-cured acrylic system exhibited a glass transition temperature (T_g) increase to 56 °C from 31 °C of the uncrosslinked copolymer. In the tested range of 10–25 wt% of PSZ, the formulation containing 20 wt% PSZ achieved a 97.9% degree of crosslinking. Compared to traditional diisocyanate-crosslinked systems, better adhesive performance was obtained with maximum tensile shear strength values of 4.4 MPa for wood substrates (substrate failure) and up to 4.0 MPa for aluminum substrates. These findings confirm that PSZ enhances the mechanical properties of acrylic adhesives, offering optimal performance and ease of application and underscoring their practical utility.