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Chemical improvement of surfaces. Part 6: enhanced flame retardancy of Scots pine sapwood by covalent modification with phosphorus and boron functionalized benzoates

Christopher Ehrhardt, Marco Tapken, Jan C. Namyslo and Dieter E. Kaufmann ORCID logo
From the journal Holzforschung


The broad applicability of the wood modification protocol recently published by Kaufmann et al. allows to improve the fire resistance of renewable materials, too. In this study organophosphorus and organoboron compounds have been synthesized, characterized and subsequently applied for enhanced flame retardancy of wood. Wood hydroxyl groups of Scots pine (Pinus sylvestris L.) sapwood veneer chips were covalently modified upon esterification with benzotriazolyl-activated P- and B-substituted benz-amides. The efficacy of this synthetic strategy was demonstrated by the weight percent gain (WPG) of up to 32% and the corresponding quantities of covalently bonded organicmaterial (QCO) of up to 1.1 mmol/g, respectively. The successful covalent attachment of the functional precursors was proven by attenuated total reflection infrared spectroscopy (ATR-IR). The effect of the flame retardants on the properties of the modified sapwood samples was shown by a significant decrease of the temperature of mass loss from about 346–248 °C in the thermogravimetric analysis (TGA).

Corresponding author: Dieter E. Kaufmann, Institute of Organic Chemistry, Clausthal University of Technology, Leibnizstr. 6, D-38678 Clausthal-Zellerfeld, Germany; and Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld, Germany, E-mail:

Funding source: Clausthal University of Technology


We appreciate the support given by the Institute of Technical Chemistry, Clausthal University of Technology (Germany), for thermogravimetric analyses. We thank Marko Spillner for technical assistance. We gratefully acknowledge H. Militz and C. Mai from the section of Wood Biology and Wood Products, Georg-August-University Göttingen (Germany) for providing the veneer of Scots pine sapwood.

  1. Author contribution: All the authors have accepted responsibility for the entire content of this manuscript and approved submission.

  2. Research funding: This work was financially supported by Clausthal University of Technology, Germany.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.


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Received: 2020-02-08
Accepted: 2020-04-22
Published Online: 2020-08-06
Published in Print: 2021-01-26

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