Corn starch blended polyvinyl alcohol adhesive chemically modified by crosslinking and its applicability as polyvinyl acetate wood adhesive

Environmental considerations coupled with fossil fuel depletion encouraged research community to implement green protocol by partially or fully replacing petrochemicals. This is valid in case of adhesive research and development, where partial replacement of colloidal stabilizer, polyvinyl alcohol (PVA), is replaced by an abundant and sustainable material, corn starch (S). The work here investigates the effect of adding PVA and S blends formulated for polyvinyl acetate (PVAc)-white glue for wood adhesives. To enhance overall properties, boric acid, citric acid, glyoxal, and glutaraldehyde were employed as crosslinkers at a low concentration (0.1 wt.%). The presence of free hydroxy groups of PVA-S blend provides a site for the crosslinkers. Crosslinked blends are formulated with PVAc binder, plasticizer, and preservatives forming a wood adhesive. Various characterization techniques were employed for measuring physical and thermo-mechanical properties. Crosslinking was proved with dynamic mechanical analysis. Enhancement in performance properties was shown by the increase in tensile shear strength on bonded wood substrates and wet tack analysis. Tensile strength of bonded wood after 8 h. showed 16% increment for citric acid-incorporated sample, 13% for glutaraldehyde, 8% for boric acid, and similar to 7% for glyoxal crosslinked wood adhesive. Moreover, crosslinking consolidated polymer chains, which resulted in enhanced thermo-mechanical properties. Overall, the crosslinked samples showed better physical, mechanical, and thermal properties when compared to the non-crosslinked adhesive. Hence, this study can be a potential in the further development of sustainable white glue for wood bonding applications.