Scientific paper ID 849 : 2013/3

The samples tested were of raw wood and such treated by swelling in water and dried in various temperature regimes. Measurements were performed on a microhardness tester mhp-160 kit to a NU-2 microscope and on a dynamic ultra micro hardness equipment DUH-211S. Therefore we used a methodology for determining the so-called total microhardness (MHT), enabling measurement of the imprint in loaded state that was developed by our research group. The modern depth-sensing indentation method (DSI), consists of obtaining the data from load-penetration (indentation) curves. However, these results showed a large dispersion because of the high structural heterogeneity of the material but permit a direct detection of cavities which are often in the dimensions range of the penetrating pyramid. It has been found that the treated samples have lower total resistance to penetration and that increasing the penetration depth increases the microhardness. The latter is associated with a local material lute in the process of penetration. A hypothesis based on changes in the hydrogen bonds between cellulose molecules during the treatment has been proposed for the explanation of the experimental results.