Engineering of open assembly time of water-based polyvinyl acetate (PVAc) wood adhesives by post-addition of additives

Polyvinyl acetate (PVAc) as a thermoplastic polymer is one of the most common wood adhesive types for interior applications. For the processing of water-based PVAc wood adhesives, certain manufacturer-related parameters such as open and closed assembly time must be considered in order to avoid loss in strength properties of the adhesive joint. As for some applications, the maximum open assembly time is too short, this production-related property can be engineered by adding additives to the PVAc wood adhesive. The aim of this study was to prolong the open assembly time by post-adding different additives to the adhesive. The additives used were water, calcium carbonate, D-sorbitol, fumed silica, glycerine, methylcellulose, poly dextrose, urea, wheat flour and wheat starch. Using a simple in-situ determination method, open assembly time was measured. Additionally, the solid content and the rheological behaviour as well as the mechanical properties and the moisture absorption behaviour from dried adhesive films were determined for characterisation of the additive-PVAc adhesive mixture. A preferred additive would only prolong the open assembly time and would have little to no influence on the remaining parameters investigated. This study showed, that with the post-addition of certain additives to the PVAc adhesive, the desired production-related requirements can be adjusted.