Chemical and Structural Characterization of Poplar and Black Pine Wood Exposed to Short Thermal Modification/Kemijska i strukturna obiljezja drva topole i crnog bora izlozenih kratkotrajnoj toplinskoj modifikaciji

In this study, poplar and black pine wood was exposed to short thermal treatments, aiming to improve some crucial properties. Using wet chemical analyses and Fourier-transform infrared spectroscopy (FT-IR), the influence of these treatments on the chemical composition of the modified species was investigated, as well as on the wood structure, using scanning electron microscopy. With the increase of heat treatment intensity, a mass loss of both species was recorded, attributed to the moisture loss and degradation of volatile compounds, as well as thermally less stable components. In the first treatment stages, the extractives presented a decrease, whereas with the duration and temperature increase, new extractives were formed. Lignin increased its network through ramification, especially at 200 [degrees]C, while holocellulose was found lower in all modified wood categories of both species than in unmodified wood due to the intense decomposition of hemicelluloses. The findings of FT-IR analyses were in line with the chemical analysis results. The thermal modification process made wood materials more hydrophobic and dimensionally stable, providing protection against decomposing factors. At the same time, they were not intensively thermo-degraded, which increased their utilization perspectives and application range as solid wood of enhanced properties, or as wood particles/fibers participating as raw materials in wood-based composite products, wood-polymers composites etc., enhancing their materials compatibility, properties and performance. Keywords: cellulose; chemical composition; FTIR; lignin; thermal treatment; wood U radu se opisuje istrazivanje izlaganja drva topole i crnog bora kratkotrajnim toplinskim tretmanima radi poboljsanja nekih njihovih kljucnih svojstava. Utjecaj tih postupaka na kemijski sastav modificiranih vrsta drva istrazen je primjenom mokre kemijske analize i Fourierove transformirane infracrvene spektroskopije (FT-IR), a utjecaj na strukturu drva odreden je uz pomoc pretraznoga elektronskog mikroskopa. Povecanjem intenziteta toplinskog tretmana zabiljezen je gubitak mase obiju vrsta drva koji je pripisan gubitku vode te razgradnji hlapljivih i toplinski nestabilnih spojeva. U prvim fazama tretmana smanjio se udio ekstraktiva, dok su se s produljenjem tretmana i povecanjem temperature stvarali novi ekstraktivi. Lignin je povecao svoju umrezenost razgranjivanjem, posebno na 200 [degrees]C, dok je udio holoceluloze bio manji u modificiran