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The effect of urea-formaldehyde resin pre-cure on the internal bond of medium density fiberboard

Einfluss des Vorhärtens von UF-Harzen auf die Querzugfestigkeit von MDF

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Abstract

The effect of elapsed time between resin blending and hot pressing stage on the degree of resin pre-cure is not known in the manufacture of medium density fiberboard (MDF). This phenomenon of resin pre-cure is a clear factor that should be taken into account in MDF manufacture. An experiment which used differential scanning calorimetry (DSC) to quantify resin pre-cure degree after resin blending, and the relationship between resin pre-cure degree and the internal bond strength (IB) of MDF has been conducted. The results indicated that the rate of pre-cure process after resin blending at room temperature (23°C) under constant humidity and temperature conditions included three stages. In the first stage, the rate of pre-cure reaction was close to that of at the third stage, but lower than that of the second stage. The decrease of corresponding IB strength for boards made with material having undergone such pre-cure was very sharp during the first 24 h. After 24 h, the IB decrease displayed a linear relationship with time. The IB displayed a linear relationship with the resin pre-cure degree, as evaluated by DSC.

Zusammenfassung

Der Einfluss der Verweildauer zwischen Harzmischung und Heißpressen auf den Grad des Vorhärtens beim Herstellen von MDF ist nicht bekannt. Das Phänomen des Vorhärtens ist ein deutlicher Faktor, der bei der MDF-Herstellung berücksichtigt werden sollte. Es wurden Versuche durchgeführt, die mit Hilfe der Differential-Kalorimetrie (DSC) den Grad des Vorhärtens nach dem Harzmischen und dessen Einfluss auf die Querzugfestigkeit (IB) quantifizieren. Die Ergebnisse zeigen, dass die Reaktion des Vorhärtens bei konstanter Feuchtigkeit drei Stufen durchläuft. In der ersten Phase ist die Aushärtungsgeschwindigkeit gleich hoch wie bei der dritten, jedoch geringer als in der zweiten Phase. Der Abfall der Querzugfestigkeit von Platten nach solchem Vorhärten war sehr steil während der ersten 24 h. Nach 24 h verläuft dieser Abfall linear mit der Zeit, wie aus den DSC-Untersuchungen hervorgeht.

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Acknowledgements

The authors greatly appreciate Forintek Canada Corp., Québec for supplying materials. C. Xing thanks Natural Sciences and Engineering Research Council (NSERC) and Laval University for financial support for this study.

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Authors and Affiliations

  1. Forintek Canada Corp., 319 rue Franquet, Québec G1P 4R4, Canada

    Cheng Xing

  2. Département des Sciences du Bois, Faculté de foresterie et de géomatique, CERSIM, Université Laval, Ste-Foy, Québec G1K 7P4, Canada

    Bernard Riedl

  3. Département des Sciences du Bois, Faculté de foresterie et de géomatique, Université Laval, Ste-Foy, Québec G1K 7P4, Canada

    Alain Cloutier

  4. University of Toronto, Toronto, Canada

    Guangbo He

Authors
  1. Cheng Xing
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  2. Bernard Riedl
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  3. Alain Cloutier
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  4. Guangbo He
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Correspondence to Bernard Riedl.

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Xing, C., Riedl, B., Cloutier, A. et al. The effect of urea-formaldehyde resin pre-cure on the internal bond of medium density fiberboard. Holz Roh Werkst 62, 439–444 (2004). https://doi.org/10.1007/s00107-004-0512-z

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  • DOI: https://doi.org/10.1007/s00107-004-0512-z

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