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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

Abstract

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

Acknowledgments

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.

References

Drafz, M.H.H., Dahle, S., Maus-Friedrichs, W., Namyslo, J.C., and Kaufmann, D.E. (2012). Chemical improvement of surfaces. Part 2: permanent hydrophobization of wood by covalently bonded fluoroorganyl substituents. Holzforschung 66: 211–216, https://doi.org/10.1515/hf-2011-0216.Search in Google Scholar

Friesen, C.M., Montgomery, C.D., and Temple, S.A.J.U. (2012). The first fluorous biphase hydrogenation catalyst incorporating a per- fluoropolyalkylether: [RhCl(PPh2(C6H4C(O)OCH2CF(CF3)-(OCF2CF(CF3))nF))3] with n=4–9. J. Fluor. Chem. 144: 24–32, https://doi.org/10.1016/j.jfluchem.2012.09.001.Search in Google Scholar

Gao, M. (2004) Thermal degradation of wood treated with amino resins and amino resins modified with phosphate in nitrogen. J. Fire Sci. 22: 505–515, https://doi.org/10.1177/0734904104043031.Search in Google Scholar

Gao, M. and Sun, C.Y. (2003). Study on the thermal degradation of wood treated with amino resin and study on the thermal degradation of wood treated with amino resin and amino resin modified with phosphoric acid. J. Fire Sci. 21: 189–201, https://doi.org/10.1177/0734904103021003002.Search in Google Scholar

Gao, M., Niu, J., and Yang, R. (2006). Synergism of GUP and boric acid characterized by cone calorimetry and thermogravimetry. J. Fire Sci. 24: 499–511, https://doi.org/10.1177/0734904106061522.Search in Google Scholar

Green, J. (1992). A review of phosphorus-containing flame retardants. J. Fire Sci. 10: 470–487, https://doi.org/10.1177/073490419201000602.Search in Google Scholar

Hill, C.A.S. (2006). Wood modification. Chemical, thermal and other processes. John Wiley & Sons (Wiley series in renewable resources), Chichester, England, Hoboken, NJ.Search in Google Scholar

Hirata, T. (1987). Thermal analysis of cellulose treated with boric acid or ammonium phosphate in varied oxygen atmospheres. J. Appl. Polym. Sci. 33: 1533–1556, https://doi.org/10.1002/app.1987.070330510.Search in Google Scholar

Kaldun, C., Dahle, S., Maus-Friedrichs, W., Namyslo, J.C., and Kaufmann, D.E. (2016). significantly enhanced hydrophobicity of wood by covalent modification with p-silyl-functionalized benzoates. Holzforschung 70: 411–419, https://doi.org/10.1515/hf-2015-0036.Search in Google Scholar

Kaldun, C., Söftje, M., Namyslo, J.C., and Kaufmann, D.E. (2019). Chemical improvement of surfaces. Part 5: surfactants as structural lead for wood hydrophobization – Covalent modification with p-alkylated benzoates. Holzforschung 73. (published online 12 September 2019), https://doi.org/10.1515/hf-2019-0196.Search in Google Scholar

Kumar, A., Ye, G., Ahmadibeni, Y., and Parang, K. (2006). Synthesis of polymer-bound 4-acetoxy-3-phenylbenzaldehyde derivatives: applications in solid-phase organic synthesis. J. Org. Chem. 71: 7915–7918, https://doi.org/10.1021/jo061328z.Search in Google Scholar

Levchik, S.V. (2006). A review of recent progress in phosphorus-based flame retardants. J. Fire Sci. 24: 345–364, https://doi.org/10.1177/0734904106068426.Search in Google Scholar

Lowden, L.A. and Hull, T.R. (2013). Flammability behavior of wood and the methods for its reduction. J. Fire Sci. Rev. 2: 1–19, https://doi.org/10.1186/2193-0414-2-4.Search in Google Scholar

Munoz, A., Hubert, C., and Luche, J.-L. (1996). One-pot synthesis of phosphonic acid diesters. J. Org. Chem. 61: 6015–6017, https://doi.org/10.1021/jo951308p.Search in Google Scholar

Namyslo, J.C. and Kaufmann, D.E. (2009). Chemical improvement of surfaces. Part 1: novel functional modification of wood with covalently bound organoboron compounds. Holzforschung 63: 627–632, https://doi.org/10.1515/hf.2009.112.Search in Google Scholar

Namyslo, J.C., Kaufmann, D.E., Mai, C., and Militz, H. (2015). Chemical improvement of surfaces. Part 3: covalent modification of scots pine sapwood with substituted benzoates providing resistance to aureobasidium pullulans staining fungi. Holzforschung 69: 595–601, https://doi.org/10.1515/hf-2014-0086.Search in Google Scholar

Pries, M. and Mai, C. (2013). Fire resistance of wood treated with a cationic silica sol. Eur. J. Wood Wood Prod. 71: 237–244, https://doi.org/10.1007/s00107-013-0674-7.Search in Google Scholar

Ramiah, M.V. (1970). Thermogravimetric and differential thermal analysis of cellulose, hemicellulose, and lignin. J. Appl. Polym. Sci. 14: 1323–1337, https://doi.org/10.1002/app.1970.070140518.Search in Google Scholar

Wang, L., Zhang, T., Yan, H., Peng, M., and Fang, Z. (2013). Modification of ramie fabric with a metal-ion-doped flame-retardant coating. J. Appl. Polym. Sci. 129: 2986–2997, https://doi.org/10.1002/app.39015.Search in Google Scholar

Wang, Z., Wu, W., Zhong, Y., Ruan, M., and Hui, L.L. (2015). Flame-retardant materials based on phosphorus-containing polyhedral oligomeric silsesquioxane and bismaleimide/diallylbisphenol A with improved thermal resistance and dielectric properties. J. Appl. Polym. Sci. 132, https://doi.org/10.1002/APP41545.Search in Google Scholar

Xu, J.Z., Gao, M., Guo, H.Z., Liu, X.L., Li, Z., Wang, H., and Tian, C.M. (2002). Study on the thermal degradation of cellulosic fibers treated with flame retardants. J. Fire Sci. 20: 227–235, https://doi.org/10.1177/0734904102020003905.Search in Google Scholar

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

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