Starch-sugar synergy in wood adhesion science: basic studies and particleboard production

Abstract

Synergic properties between starch and sugar were discovered. 100% crop-based starch and sugar formulations were studied. Classical preliminary tests such as curing temperature and gel time were measured for different starch-sucrose water suspensions. More significant information was deducted with applied tests such as plywood gluing tests and particleboard production. Wood-to-wood bonding properties were analysed applying NaOH and high temperature (180°C) as catalysts for starch gelification. Comparable strength to commercial urea-formaldehyde and polyvinyl acetate adhesives was achieved in plywood tests. Consequently, the knowledge acquired in wood bonding of flat surfaces was applied to particleboard production. These derived particleboards showed that it is possible to obtain a panel with only carbohydrates as gluing agent. Starch-sugar synergy in alkaline environment increases the internal bond (IB) of the natural panels up to 0.25 N/mm2. Possible mechanisms of synergy between these saccharides were proposed. Finally, a blended formulation with Mimosa tannin allows for achieving an internal bond of 0.40 N/mm2, which is the required value for interior grade particleboards (DIN EN 312). Starch-sugar-tannin adhesives are 100% environmentally-friendly formulations.