Non-toxic, zero emission tannin-glyoxal adhesives for wood panels

Abstract

In this study different tannin-glyoxal glue mixes for particleboard were studied. Gel times at 100°C of 45% water solutions of commercial pine tannin extract (Pinus radiata ex Diteco Ltda, Chile) with respectively 8% paraformaldehyde and 9% glyoxal were done at different pHs. Duplicate one layer laboratory particleboards were prepared by adding 12% total resin solids of adhesives composed of commercial pine tannin extract (Pinus radiata ex Diteco Ltda, Chile) with paraformaldehyde, or glyoxal or polymeric 4,4' diphenylmethanne diisocianate (pMDI), respectively. It was found that tannin-glyoxal panels which do not contain formaldehyde and with an emission equal to that of unbounded wood can be obtained by the use of glyoxal as hardener.