Effects of adding nano-clay on performance of polyvinyl acetate (PVA) as a wood adhesive

Polyvinyl acetate (PVA), a thermoplastic polymer, has poor performance at elevated temperatures and humid conditions as a wood adhesive. Two types of hydrophilic nano-clay were mixed at different loadings (1%, 2% and 4%) with PVA to improve the performance of PVA towards water and elevated temperatures. The properties of PVA-clay nanocomposites were characterized by measuring the shear strength of wood block shear-type assemblies bonded with new formulated adhesives in dry and wet, and also, at elevated temperatures. Thermal stability and structure of the PVA-clay nanocomposites were studied by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that shear strength of wood joints increased in all states by adding nano-clay to PVA. Inclusion of nano-clay improved the thermal stability of PVA to different degrees depending on nano-clay loading and type. The morphological studies revealed that the fluctuations observed in thermal stability and bond strength of the nanocomposites stem from dispersion quality of nano-clay.