Thermally modified Scots pine and Norway spruce wood as substrate for coating systems

Michael Altgen*, Holger Militz

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

15 Citations (Scopus)


Thermally modified wood (TMW) is increasingly used in exterior applications as an alternative to tropical hardwoods or wood impregnated with biocides. Despite its enhanced biological durability and dimensional stability, a surface treatment of TMW with coating systems can be required in certain applications. This study assessed material characteristics of Norway spruce and Scots pine wood that was thermally modified according to the ThermoWood® process and their effect on the performance of commercially available coating systems: a solventborne oil, a waterborne alkyd-reinforced acrylate paint and a waterborne acrylate paint. Residual extractives and remaining degradation products found in TMW, carry the risk of causing discoloration or of interfering with the curing reactions of coating systems. The penetration of coating systems into TMW was not found to differ from unmodified wood, although an excessive penetration of solventborne oil was found occasionally for TMW. The adhesion strength of waterborne coatings depended on the system that was used. While one system performed sufficiently on TMW, the other coating systems showed a considerable reduction in adhesion strength already after a mild treatment (<200°C). This reduction could not be attributed to the increase in hydrophobicity of TMW that was evident from contact angle measurements, but was rather related to the mechanical interaction of the specific substrate/coating system.

Original languageEnglish
Pages (from-to)531-541
Number of pages11
Issue number3
Publication statusPublished - 1 May 2017
MoE publication typeA1 Journal article-refereed


  • Adhesion strength
  • Coating penetration
  • Material characteristics
  • Solventborne oil
  • Waterborne coating systems


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