Holz als Roh- und Werkstoff

, Volume 49, Issue 6, pp 221–228 | Cite as

Acetylated, isocyanate-bonded flakeboards after accelerated aging

Dimensional stability and mechanical properties
  • C. B. Vick
  • A. Krzysik
  • J. E. WoodJr.
Forschung und Praxis

Abstract

To improve flakeboard dimensional stability and mechanical properties for long-term exterior exposure, we fabricated and tested a highly durable isocyanate-bonded acetylated flakeboard. Flakeboards were tested for internal bond strength, thickness swell, modulus of elasticity, modulus of rupture, and breaking strength in bending, after two severe accelerated aging tests. Flake design, flakeboard density, resin content, and their interactions were critical to the performance of acetylated flakeboards in the aging tests. In bending tests, the longer disc-cut flakes produced much higher strength values than did the ring-cut flakes. In internal bond strength tests, the ring-cut flakes performed comparably to the disc-cut flakes. However, ring-cut flakes contributed somewhat more to reducing thickness swell than did disc-cut flakes. Acetylated flakeboards fabricated at high density were much stronger than those fabricated at low density. However, the high-density boards developed more thickness swell than did the low-density boards. The 5-% resin content contributed little to increased strength values in the bending tests, but this level of resin significantly improved flakeboard performance internal bond strength and thickness swell tests. Acetylation did not interfere to any practical degree with the isocyanate resin, and all property values were enhanced by acetylation, particularly internal bond strength and resistance to thickness swell.

Aceylierte, Isocyanat-gebundene Spanplatten nach beschleunigter Alterung: Dimensionsstabilität und mechanische Eigenschaften

Zusammenfassung

Um die Dimensionsstabilität und die mechanischen Eigenschaften für die Außenanwendung zu verbessern, wurden Isocyanat-gebundene Spanplatten aus acetylierten Spänen hergestellt. Getestet wurden Querzugfestigkeit, Dickenquellung, Elastiziätsmodul, Bruchspannung und Biegefestigkeit nach zweimaliger beschleunigter Alterung. Spandimensionen, Plattendichte und Festharzanteil erwiesen sich als die wichtigsten Einflußgrößen für das Testverhalten bei der beschleunigten Alterung. Späne aus dem Flachscheiben-Zerspaner führten zu höheren Festigkeitswerten als Späne nach Messerring-Zerspanung, während die Querzugfestigkeit bei beiden Spantypen vergleichbar war. Die Späne aus dem Ringzerspaner hatten jedoch einen größeren Einfluß auf die Reduzierung der Dickenquellung. Hochverdichtete Platten wiesen höhere Festigkeitswerte auf als Platten geringerer Dichte, allerdings war bei ihnen gleichzeitig die Dikkenquellung ausgeprägter. Der Festharzanteil von 5% trug wenig dazu bei, die Biegefestigkeit zu erhöhen, verbesserte aber wesentlich Dickenquellung und Querzugfestigkeit. Die Acetylierung hatte keine erkennbare Störung der Isocyanat-Verleimung zur Folge. Alle Plattenkennwerte wurden durch die Acetlierung verbessert, insbesondere Querzugfestigkeit und Dickenquellung.

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • C. B. Vick
    • 1
  • A. Krzysik
    • 1
  • J. E. WoodJr.
    • 1
  1. 1.Forest Products LaboratoryUSDA Forest ServiceMadisonUSA

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