Beneficial in-situ incorporation of nanoclay to waterborne PVAc/PVOH dispersion adhesives for wood applications

Nanoclay/polyvinyl acetate waterborne adhesives were prepared by using a two-step polymerization process. First, seed polymer particles containing the clay were obtained by batch miniemulsion polymerization. Then, the clay was buried within the particles by the addition of a neat monomer in the second step. The final stable dispersions could have up to 50 wt% of solids content. TEM images clearly showed the presence of clay inside the polymer colloids, although not totally exfoliated. The addition of nanoclay produced adhesives with higher water and heat resistance judged by the water swelling behavior and thermal degradation properties, which was reflected also in their better adhesive performance under wet conditions (D3 tests according to EN204) and high temperatures (WATT91) of the samples containing clay with respect to the pristine dispersions.