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    CORRELATION BETWEEN THE CHEMICAL COMPOSITION OF WOOD AND THE INCREASING OF ITS CALORIFIC VALUE THROUGH HEAT TREATMENT
    (Polytechnic Institute of Viseu, 2026) Domingos, Idalina; Ferreira, Miguel; Ferreira, José; Dulyanska, Yuliya; Ayata, Umit; Esteves, Bruno
    Introduction: The greatest importance of biomass lies in its Higher Heating Value (HHV), when considered for energy production. The calorific value is significantly affected by the changes in the chemical composition of the wood that occur during heat treatment. Objective: To understand the effect of heat treatment on the calorific value of the chemical constituents of two hardwoods: Sapelli and chestnut, and two softwoods: Scots pine and Siberian pine. Methods: The calorific value was determined by a Parr calorimeter – model 6400. The content of extractives was determined by successive Soxhlet extraction using about 3 g of each sample and 150 ml of dichloromethane, ethanol, and water as solvents. The extractives content was determined in accordance with TAPPI 204, and insoluble lignin by the Klason method Tappi T 222 om-02. For the determination of holocellulose, the acid chlorite method was used. Results: The calorific value of untreated wood ranged from 18.98 MJ/kg for chestnut to 20.35 MJ/kg for Siberian pine. Heat treatment resulted in an increase in the calorific value for most of the wood samples studied. Conclusion: The rise in HHV observed during heat treatment in softwoods and hardwoods is mainly due to the increase in lignin content, although dichloromethane extractives also play an important role. © 2026, Polytechnic Institute of Viseu. All rights reserved.
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    SURFACE ROUGHNESS AND SHORE-D HARDNESS OF SIX TROPICAL HARDWOODS
    (Polytechnic Institute of Viseu, 2026) Ayata, Umit; Domingos, Idalina; Ferreira, José; Cruz-Lopes, Luísa; Esteves, Bruno
    Introduction: This study investigates the Shore-D hardness and surface roughness characteristics of six tropical wood species: Canelo (Nectandra spp.), Limbali (Gibertiodendron dewevrei), Difou (Morus mesozygia), Curupay (Anadenanthera macrocarpa), Ebiara (Berlinia bracteosa), and Zwarte kabbes (Diplotropis martiusii), aiming to assess their suitability for high-performance applications. Objective: To evaluate how wood species and sanding processes influence the mechanical properties and surface quality of selected tropical woods. Methods: Samples were conditioned and sanded using abrasives of different grit sizes (80, 100, 120, 150, and 180). Surface roughness parameters Ra, Rq, and Rz, as well as Shore-D hardness, were measured. Statistical analyses were performed using ANOVA and Duncan’s test. Results: Statistical analysis revealed that abrasive grit size significantly affected surface roughness (p < 0.001), with finer grits producing smoother surfaces. Wood species also had a significant effect on both roughness and hardness. Sanding had the greatest influence on Ra, Rq, and Rz parameters. Ebiara exhibited the smoothest surface, while Curupay showed the highest hardness (74.65). Conclusion: Surface roughness is primarily influenced by sanding grit, whereas hardness is determined by wood species. The results emphasize the importance of tailoring sanding procedures to the wood species in order to optimize surface quality and mechanical performance in industrial and decorative applications. © 2026, Polytechnic Institute of Viseu. All rights reserved.