Formaldehyde release of tannin-bonded particleboards

The formaldehyde release of tannin-based adhesives was investigated. Predominantly, formaldehyde emissions were dependent on the molar ratio of tannin to formaldehyde. Using standard curing conditions, the formaldehyde release of cured resins increased significantly at a molar ratio above one (more tan 10.5% formaldehyde). Furthermore, the emission rate was influenced by purity and type of the tannin and by reactivity and pH of the glue. The formaldehyde release of industrial and laboratory produced particleboards bonded with different tannin-based adhesives was determined by gas-analysic, perforator, and WKI methods. Most of the tested particleboards had a low formaldehyde content belonging to German emission class E2. From test results, correlation curves between the different analyzing methods were calculated.