PEER-REVIEWED ARTICLE bioresources.com Hrčka et al. (2018). “Oak wood properties,” BioResources 13(4), 8885-8898. 8885 Correlations between Oak Wood Properties Richard Hrčka, a, * Viera Kučerová, b and Tatiana Hýrošová c Correlations between the chemical composition and physical properties of oak wood were studied by correlation analysis. The specimens were produced from thermally treated oak wood at temperatures of 20 °C, 160 °C, 180 °C, 210 °C, and 240 °C. The physical properties were affected by the chemical composition of oak wood. The correlations of equilibrium moisture content (EMC) and oak density at EMC were similar, in accordance with the investigated properties. Oak end hardness was affected by treatment temperature. The depth of indentation significantly affected the hardness. Mass specific heat capacity and effusivity were positively correlated with EMC, sugars, holocellulose, cellulose traits, and ash and negatively affected by total extractives. Thermal diffusivity was slightly affected by treatment temperature. Keywords: Oak wood; Heat treatment; Correlation; Chemical composition; Macromolecular traits of cellulose; Physical properties Contact information: a: Department of Wood Science; b: Department of Chemistry and Chemical Technologies; c: Department of Mathematics and Descriptive Geometry, Technical University in Zvolen, T. G. Masaryka 24, 960 53 Zvolen, Slovak Republic; *Corresponding author: hrcka@tuzvo.sk INTRODUCTION The logging and utilization of oak wood are traditional and have been known since ancient times (Sinković et al. 2009; Welling et al. 2018). Recently, Ruiz-Aguino et al. (2018) mentioned that approximately 400 species of Quercus are widely recognized. From a macroscopic point of view, surely Turkey oak wood can be recognized, relative to other oak woods, based on the color and morphology of the wood rays. Turkey oak is less utilized because it is prone to cracks and possible formation of false heartwood. Some research has been directed towards the processing of Turkey oak wood (Tolvaj and Molnár 2006; Todaro et al. 2012) with a goal to find the optimum procedure for Turkey oak wood valorization (Ferrari et al. 2013). The associated problems with the growth and utilization of Turkey oak are not as frequent as pedunculated or sessile oaks (Makovíny 2010). This probably was the reason for the decision to cultivate oaks in Slovakia. Currently, most oak wood production comes from pedunculated or sessile oak species in Slovakia (MARD 2017). Oak wood properties are widely appreciated. The measurements of some wood properties are difficult; therefore, there is an effort to correlate the properties and determine their values indirectly. Moreover, the overall character of wood is characterized by a set of independent properties. The correlations clarify the behavior of wood after processing. The elevated surrounding temperature and the possible heat flow to wood volume is an example of such processing (Militz 2002; Gérardin 2016). The different procedures in the cited work showed different results for wood properties and the wood exhibited more diversity and utilization possibilities. The chemical composition influences wood properties. For example, the equilibrium moisture content of wood is proportional to free hydroxyl groups