Dynamic strength properties and structural integrity of wood modified with cyclic N-methylol and N-methyl compounds

Lukas Emmerich; Christian Brischke; Susanne Bollmus; Holger Militz

doi:10.1515/hf-2021-0013

Article

Dynamic strength properties and structural integrity of wood modified with cyclic N-methylol and N-methyl compounds

Lukas Emmerich , Christian Brischke , Susanne Bollmus and Holger Militz

Published/Copyright: April 28, 2021

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From the journal Holzforschung Volume 75 Issue 10

Abstract

Cyclic N-methylol compounds have been used for cell wall impregnation modifications of wood. Besides an improved decay resistance and dimensional stability, the modifications resulted in a decrease of wood’s dynamic strength properties. However, the mechanisms behind a significant loss in dynamic strength are not fully understood yet. In this study, wood blocks were treated with the N-methylol compounds 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and methylated DMDHEU (mDMDHEU) and the N-methyl compound 1,3-dimethyl-4,5-dihydroxy-ethyleneurea (DMeDHEU). In order to study the factors that control the changes of wood performance under dynamic loads, single (impact bending strength, IBS) and multiple dynamic impact (resistance to impact milling, RIM) tests were applied. It became evident, that reductions in IBS and RIM increased with increasing solid content, formaldehyde content and catalyst concentration of the impregnation solutions, but were not affected by a cold-water leaching. Differences in structural integrity of wood modified with N-methylol and N-methyl compounds were more pronounced than those of IBS. Therefore, RIM appeared more sensitive to changes on cellular level, as a higher degree of co-condensation of the N-methylol compounds with cell wall polymers was expected in comparison with the N-methyl compound.

Keywords: DMDHEU; DMeDHEU; impact bending strength; mDMDHEU; resistance to impact milling; structural integrity

Corresponding author: Lukas Emmerich, Wood Biology and Wood Products, University of Goettingen, Buesgenweg 4, D-37077Goettingen, Germany, E-mail: lukas.emmerich@uni-geottingen.de

Acknowledgments

The authors acknowledge and cordially thank Alexander Ehrmann, Tobias Gerbershagen, Nicklas von Boch-Galhau, Brendan Marais and Maja Bleckmann for assistance with the mechanical tests. The Archroma Management GmbH is acknowledged for providing the modification chemicals.

Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

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Received: 2021-01-21

Accepted: 2021-03-23

Published Online: 2021-04-28

Published in Print: 2021-10-26

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Keywords for this article

DMDHEU; DMeDHEU; impact bending strength; mDMDHEU; resistance to impact milling; structural integrity