Abstract
Exterior grade particleboard satisfying the requirements of the V100 test, of formaldehyde emission well within the emission standard E1 class, and of pressing times as fast as 8.5 sec/mm can be produced at higher moisture contents using fast-reacting non-modified and non-fortified procyanidin/prodelphinidin tannin extracts such as pine bark tannin extract and pecan nut pith tannin extract. Such results, under the conditions reported are not achieved with the slower reacting tannins traditionally associated with the practice of tannin adhesives. The results reported establish that the faster is the reaction of the tannin with formaldehyde, the lower is the amount of formaldehyde needed to achieve V100 standard, the lower is the formaldehyde emission, the faster is the pressing time achievable and the higher is the tolerance of the adhesive to high moisture content of the resinated wood particles.
Zusammenfassung
Aus Birkenrinde und Hickory-Nüssen wurden Tannine extrahiert. Mit diesen schnell reageierenden, nicht midifizierten und nicht verstärkten Procyanidin/Prodelphinidin-Tanninen können mit Preßzeiten von nur 8.5 sec/mm und bei rel. hoher Feuchte E1-Span-platten hergestellt werden, die dem V100 Standard genügen und für Außenverwendung geeignet sind. Diese Ergebnisse können nicht mit den bisher bekannten Verfahrenider Tanninverleimung erreicht werden. Je rascher die Tannine mit Formaldehyd reagieren, desto weniger Formaldehyd wird benötigt, um den V100-Standard zu erreichen, desto geringer ist dementsprechend die Formaldehydemission. Zusätzlich wird auch die Preßzeit verringert, und die Beständigkeit des Harzes genenüber Spänen mit hohem Feuchtegehalt erhöht.
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References
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Pizzi, A., Valenezuela, J. & Westermeyer, C. Low formaldehyde emission, fast pressing, pine and pecan tannin adhesives for exterior particleboard. Holz als Roh-und Werkstoff 52, 311–315 (1994). https://doi.org/10.1007/BF02621421
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DOI: https://doi.org/10.1007/BF02621421