ln parts 3 and 4, we will now study the different chemical types of adhesives which are specifically used in Woodworking and furniture, we will provide their technical characteristics and explain for which applications they are used. ln this part 3 we will begin with the emulsion based adhesives, PVAc, copolymers aod VAE emulsions.
Vinyl emulsions or dispersions are also called white glues or poly vinyl acetate ( PVAc). They are made by polymerization of vinyl acetate monomer , with or without copolymers, as a water emulsion or dispersion, and the base emulsion has usually a solids ratio around 56 %.
PVAc is fairly hard and cohesive because steric hindrance between alternate acetate groups restricts movement of the molecules.
We can also understand that the pendant acetate groups can be hydrolysed by alkalis and water and this will proceed fairly quickly along the molecule chain.
Normally, PVAc is a thermoplastic polymer, but we will see later that it may be crosslinked in order to improve its water resistance.