Use of spruce tannin as a binder in particleboards and medium density fibreboards (MDF)

In the recent past increasing attention has been paid to the use of natural adhesives as a binder in the wood-based panel industry. Nowadays, two german companies are using Quebracho tannin and Wattle tannin for the production of particleboards and medium density fibreboards (MDF), respectively. Up-to-now no serious attention has been given to bond fibreboards by tannin derived from spruce bark. Results of research work carried out in the last two years are presented on the use of spruce tannin as a binder for medium density fibreboards. The results reveal that spruce tannin can be used to partially substitute Quebracho tannin in MDF up to about 60 %. Such boards still meet the specification of moisture resistant MDF (according to EN 319 and EN 321). Moreover, spruce tannin can be used to 100 % as a binder for the production of MDF for indoor use (type MDF EN 622-5). Furthermore, it was shown that postthermal treatment of the MDF bended by spruce tannin has a significant positive effect on both thickness swelling and formaldehyde release