| Summary: | One of the most important by-products generated in the forestry industry is the bark obtained during the debarking process. Pine (<i>Pinus radiata</i> D. Don) and eucalyptus (<i>Eucalyptus globulus</i> L.) are the main important tree species exploited in the Chilean forestry industry. The bark of <i>P. radiata</i> D. Don is an interesting source of extracts, rich in condensed tannins, with potential uses in biopolymer and bioadhesive preparation. Conversely, the <i>E. globulus</i> bark extracts are rich in hydrolyzable tannins with few applications. Nevertheless, the forest industry generates a high volume of these by-products, simultaneously. Then, it is interesting to determine a suitable process for the joint valorization of both forest by-products at a large scale. In this work, alkaline extraction (NaOH and Na<sub>2</sub>SO<sub>3</sub>) was performed at a pilot scale of a mixture of <i>E. globulus</i> and <i>P. radiata</i> barks prepared at different ratios (0%–100%). The effect of bark mixture composition on the resulting extract’s properties was evaluated. All extracts were characterized according to their chemical composition by FTIR-ATR, MALDI-TOF, and molecular weight distribution (GPC). In addition, the Stiasny number was tested to determine the potential use of extracts in bioadhesive formulation. The self-condensation reaction of resulting extracts was studied using Dynamic Mechanical Analysis (DMA) and Automated Bond Evaluation System (ABES) techniques. Results show a good interaction between condensed and hydrolyzable tannins from both species’ barks. It also demonstrated the potential application of the obtained extracts, for a bark ratio of 50:50, in the formulation of bioadhesives for particleboard manufacture. The obtained product showed a similar performance to that of the bioadhesive formulated with the extract obtained using only <i>P. radiata</i> bark.
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