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Key message: Lambro, Brenta, Taro, Alcinde and Soligo are new poplar cultivars suitable for laminated veneer lumber (LVL) for structural purposes. While Lena, Koster, Dvina, Mella and Trichobel must be used with careful veneer material selection to obtain high value of mechanical properties. Context In France, the veneer processing industry uses only a very small number of different poplar cultivars. Aims: This paper set out to investigate the potential of laminated veneer lumber made from 14 new cultivars for structural purposes, with a focus on juvenility and veneer thickness effects. Methods: The mechanical properties of laminated veneer lumber panels made from each cultivar (114 samples per cultivar) were characterized by measuring their density, modulus of elasticity and modulus of rupture. Results: A tight correlation was found between destructive and non-destructive modulus of elasticity tests (R 2 = 0.90, 1,808 samples). Five cultivars had suitable mechanical properties for structural applications ('Lambro', 'Brenta', 'Taro', 'Alcinde' and 'Soligo'). Five cultivars needed to be used with careful sample selection ('Lena', 'Koster', 'Dvina', 'Mella' and 'Trichobel'), and the final four ('I214', 'A4A', 'Triplo' and 'Polargo') could not be recommended for structural purposes. Conclusion: The advantage of using veneers of mature wood compare to juvenile wood for laminated veneer lumber (LVL) production was due to an improvement of modulus of elasticity and modulus of rupture in the range of 15 to 20 %. The use of thick veneers (5.25 mm compared to 3 mm) did not appear to be detrimental to laminated veneer lumber mechanical performance. (Résumé d'auteur

Many wood processing industries use short rotation teak, which has lower quality especially in durability and dimensional stability. Heat treatment is an eco-friendly method to improve dimensional stability and durability of wood. The objectives of the study were to investigate the effects of thermal modification on chemical composition, colour, dimensional stability and durability as well as coating's performance after accelerated weathering of short and long rotation teak for exterior utilization. In this study, the samples were heated in oven at 220 °C for 20 h under nitrogen atmosphere. Results showed that independently of growth conditions teak woods underwent hemicelluloses degradation and an increase of lignin content after heat treatment. Extractives contents were lower in short rotation than in long rotation teak, and decreased in all cases after heat treatments. Dimensional stability was considerably improved as indicated by anti-swelling efficiency values of 64,9% and 58,9% for short and long rotation teak, respectively. Heated teak woods were more resistant against Trametes versicolor and the durability of short-rotation teak increased from moderate to very durable. Coatings on heat treated teaks had better bonding quality and better photo-stability when compared to unheated. Heated short rotation teak could be considered for exterior application.

For many wood cutting processes, the interest of high-speed tool steels and tungsten carbides remains very important because of their good tool edge accuracy and easy grinding. The wear of high-speed steel and tungsten carbide is an important economic parameter. Wood extractives and silica have a potential adverse effect on tool wear. Rapid chemical wearing due to corrosion and mechanical wearing has been attributed to the presence of extractives and silica in wood and wood composites. This paper presents the wear characteristics of SKH51 high-speed steel and K10 tungsten carbide caused by extractive and abrasive materials present in the lesser-known Tapi-Tapi wood and wood composites of wood cement board, particleboard, MDF, and oriented strand board (OSB). Experimental results showed that wearing of the cutting tools tested was determined by extractives and silica contained in the wood and wood composites. Wood cement board, which is high in silica content, caused severe damage to the cutting edge of the high-speed steel. A corrosion/oxidation mechanism was found to contribute to the wear of SKH51 and K10 when cutting the Tapi-Tapi wood, MDF, particleboard, wood cement board, and OSB. The silica and extractives determined the abrasion and corrosion wear mechanism to a varying degree.

Teak wood (Tectona grandis) as an important forest resource in Indonesia has been processed to wood furniture in large quantities to fulfill an increasing need of both local and international consumers. To satisfy the increasing demand for wood products, teak wood has been supplied from the State forests (Perhutani) and Community teak plantations. Community teak has been harvested at shorter age rotations (7–10 years) than Perhutani teak (40–60 years). This paper discusses the occurrence and characteristics of juvenile wood in Perhutani and Community teak based on density, shrinkage, bending strength (modulus of rupture - MOR, modulus of elasticity - MOE), fiber length, and microfibril angle (MFA). A segmented modeling approach was used to find the juvenile mature transition. Fiber length and MFA appear to be good anatomical indicators of radial increment demarcation between juvenile and mature wood, although maturation radial increment varies slightly between the fiber length and MFA. The use of radial increment density, shrinkage, MOR, and MOE were not appropriate, because of low coefficients of determination and a large range of radial increment for transition from juvenile to mature wood. The maturations were estimated to start at radial increments 10 and 14 cm from the pith by fiber length, and 11 and 15 cm from the pith by MFA for Perhutani and Community teak, respectively. The projected figures for the proportion of juvenile wood at breast height for Perhutani and Community teak were 65% and 100%, respectively. The results also indicate that short-rotation Community teak was not remarkably inferior in shrinkage, MOE and MOR compared to Perhutani teak, although it was less dense, less attractive and less durable due to lower heartwood content. Therefore, careful attention should be given to the use of the Community teak in some wood-processing technologies.

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