Study of the bonding performance of UF/PVAc formulations with low formaldehyde emission

Abstract

Urea-formaldehyde resins are still the most widely used adhesives in the manufacture of woodbased panels. However, environmental requirements, as stringent formaldehyde emissions regulations, and new products specifications, have forced producers to find new tailor-made gluingsolutions, without loosing productivity and quality. Three approaches currently been followed:optimization of UF resin synthesis, development of new catalysis systems and the combination ofhigh performance UF resins with added chemical formaldehyde scavengers [1].Another alternative is the formulation of two components systems, mixing a UF resin with aformaldehyde free adhesive, as PVAc (Polyvinyl Acetate Adhesive), an aqueous dispersion ofpolyvinyl acetate compatible with UF. PVAc based glues are very common in the furniture andjoinery applications, because they are very easy to handle and apply and they have a long storagelife. However, due to their characteristics, as the low moisture resistance and creep (thermoplasticity), the common PVAc adhesives are restricted to non-structural and interior applications [2].Modified PVAc glues with the addition of crosslinkers allowed this type of glues to be used inwater resistance classes D2 to D4 according to EN 204 standard [3].