Characterisation of tannin resin blends for particle board applications

Tannins and cashew nut shell liquid (CNSL) are groups of natural resins that are receiving wide attention as substitutes to synthetic binders in the production of biocomposites. In this work, blends of hydrolyzed tannin, CNSL, and urea formaldehyde (UF) have been tested to determine their mechanical and physical properties for particle board applications. The blending of hydrolyzed tannin with UF resin has been found to reduce the formaldehyde emission levels significantly. A blend of hydrolyzed tannin and CNSL has been found to possess better dimensional stability. Tannin-blended resins cure faster, i.e. have shorter pot life, and result in composites with better water and moisture resistance when compared to UF. Thermal analysis by differential scanning calorimetry has shown that tannin blends exhibit better thermal stability and have a higher glass transition temperature than UF resin. Generally, it was found that particle boards made from coffee husks, and bonded using the tannin resin blend that include UF and CNSL, possessed superior properties to those made using UF alone. The mechanical and physical properties of coffee husk-particle boards produced using this new resin blend are presented and discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.