Phenolic resins derived from medium boiling fraction of fast pyrolysis oil - application as wood glue for non-load-bearing wooden materials

The general potential applicability of the medium condensing fraction of fast pyrolysis vapors as substitute for phenol in Phenol-Formaldehyde-resins in wood glue application was described in an earlier study. For the present study the focus was on recipes with high degree of substitution (>60 %). The threshold value for minimum tensile strength of 10N/mm² for its application as glue in non-load-bearing wooden materials such as ply wood was exceeded for half of the tested recipes, but without clear dependence on degree of substitution. The results from DSC measurements characterizing the curing behavior of the resins showed no dependence of peak temperature on degree of substitution, so the substituted resins can be applied with a pressing temperature of about 130°C, regardless of share of pyrolysis condensate in the resin. On the other hand, the reactivity represented by released heat of reaction clearly drops with increasing degree of substitution, which indicates a necessary increase in pressing time for the production of ply wood with highly substituted resins.