Surface engineering of wood substrates to impart barrier properties: a photochemical approach

In this study, sugar maple and white pine, two species of wood commonly used in indoor and outdoor applications, were treated by photo-initiated chemical vapor deposition to impart barrier properties. After treatment, wood wettability decreased significantly, as evidenced by water contact angle measurements (from 50° to 113° for sugar maple and 87° to 172° for white pine). Further, beyond being able to repel water, the coating shows the ability to breathe, evidenced by standardized vapor sorption tests. However, accelerated weathering via ASTM G155 testing determined that the treatment could not protect the wood from photo-degradation, or retain its properties post-weathering. This treatment could therefore be best suited for wood pre-treatment in combination with other coatings

Thermal modification of wood and a complex study of its properties by magnetic resonance and other methods

© 2016, Springer-Verlag Berlin Heidelberg.Thermal modification of wood is an effective method to improve some of the properties of wood. It is reported on studies of vacuum thermal-treated wood species by magnetic resonance methods. Wood species such as Scots pine (Pinus sylvestris), birch (Betula pendula), Russian larch (Larix sibirica), Norway spruce (Picea abies), small-leaved lime (Tilia cordata) were vacuum treated by heat at 220 °C with various durations up to 8 h. This selection of wood species was investigated by electron paramagnetic resonance, nuclear magnetic resonance and microscopy methods before and after the thermal treatment. Electron paramagnetic resonance experiments revealed changes in the amount of free radicals in samples with the thermal treatment duration. Additional information on magnetic relaxation of 1H nuclei in samples at room temperature was obtained. Optical microscope analysis helped to detect structural changes in the thermally modified wood. Important properties of wood such as wood hardness and humidity absorption were also studied. The original results that were obtained correlate and complement each other, and clarify changes in the wood structure that appear with the heat treatment

Resistance of thermally modified ash (Fraxinus excelsior L.) wood under steam pressure against rot fungi, soil-inhabiting micro-organisms and termites

Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood® treatment intensity on improvement of wood decay resistance against soil-inhabiting micro-organisms, brown/white rots and termite exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170, 200, 215 and 228 °C. The reference materials were untreated ash and beech wood for decay resistance tests, untreated ash wood for soil bed tests and untreated ash, beech and pine wood for termite resistance tests. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungi according to CEN/TS 15083-1 directives. Durability against soil-inhabiting micro-organisms was determined following the CEN/TS 15083-2 directives, by measuring the weight loss, modulus of elasticity (MOE) and modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis species was used for determining the termite attack resistance by non-choice screening tests, with a size sample adjustment according to EN 117 standard directives on control samples and on samples which have previously been exposed to soil bed test. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature above 215 °C, represented by a wood mass loss (ML%) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ‘‘durable’’ or ‘‘very durable’’ in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever the heat treatment conditions are, thermally modified ash wood was not efficient against termite attack neither before nor after soft rot degradation

Comparative study of the methane production based on the chemical composition of Mangifera Indica and Manihot Utilissima leaves

Leaves of Mangifera Indica (MI, mango leaves) and Manihot Utilissima (MU, cassava leaves) are available in tropical regions and are the most accessible vegetal wastes of Kinshasa, capital of Democratic Republic of Congo. These wastes are not suitably managed and are not rationally valorized. They are abandoned in full air, on the soil and in the rivers. They thus pollute environment. By contrast, they can be recuperated and treated in order to produce methane (energy source), organic fertilizer and clean up the environment simultaneously. The main objective of this study was to investigate methane production from MI and MU leaves by BMP tests at 30°C. The yields achieved from the anaerobic digestion of up to 61.3 g raw matter in 1 l medium were 0.001 l/g and 0.100 l CH4/g volatile solids of MI and MU leaves, respectively. The yield of MU leaves was in the range mentioned in the literature for other leaves because of a poor presence of bioactive substrates, and low C/N ratio. This methane yield corresponded to 7% of calorific power of wood. By contrast, the methane yield from MI leaves was almost nil suggesting some metabolism inhibition because of their rich composition in carbon and bioactive substrates. Whereas classical acidogenesis and acetogenesis were recorded. Therefore, methane production from the sole MI leaves seems unfavorable by comparison to MU leaves at the ambient temperature in tropical regions. Their solid and liquid residues obtained after anaerobic digestion would be efficient fertilizers. However, the methane productivity of both leaves could be improved by anaerobic co-digestion.Thèse : Etude de la biodégradation anaérobie des feuilles de Mangifera Indica (manguier) et Manihot Utilissima (manioc