Open Assembly Time of Water-Borne Polyvinyl Acetate (PVAc) Wood Adhesives Affected by Various Factors

Open assembly time is one of the most important processing parameters of water-borne polyvinyl acetate (PVAc) dispersion adhesives. Exceeding the open assembly time may cause a loss of bonding properties. It is essential to have knowledge about possible factors influencing the open time. The present work evaluates different influencing factors on open assembly time of PVAc adhesives. At first, a simple and highly reproducible method was developed to determine the open time. Subsequently, by using this method, open times at varying relative humidities, room temperatures and application rates of PVAc adhesives were investigated on absorbent substrate. As a general result, this method is suitable as an alternative for determining the open assembly time. Furthermore, clear effects of some parameters investigated could be observed. While an increase in relative humidity and adhesive application rate led to a prolonged open assembly time, an increase in room temperature showed only little negative effect. However, if wood substrate and adhesive temperatures are simultaneously increased with the room temperature, a severe shortening of the open time could be observed.