Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The study is focused on the decreasing of oriented strand boards air permeability using paints.  The oriented strand boards /3 (classification according to EN 300) of 12 mm thickness was chosen for the measurement. Nine different paints were applied in one layer on one side of boards. The difference in air permeability of unpainted and painted boards was defined as paint impact in %. Paint impact ranged from 1.9 % to 78.6 %. Furthermore, the air permeability of 15 and 22 mm thick oriented strand boards /3 boards from another producer exhibiting better properties has been measured to compare. The best results of paint impact were obtained for latex paint (paint impact 78.6 %) and penetration 1 (paint impact 66.4 %). Decreasing of the air permeability of oriented strand boards applied in low-cost constructions by using inexpensive paints could significantly improve the insulating properties of the wall structure and thus contribute to the development of the concept of low-cost passive building.  

Eucalypts and Phoenix reclinata posts are the most commonly used species for fencing posts in urban areas of Uganda. Although eucalypts are known to be susceptible to termites, fencing posts are still used untreated. In this study, the effectiveness of Copper Chrome Arsenate and used engine oil in protecting Ugandan grown Eucalyptus grandis × Eucalyptus camaldulensis clone and Phoenix reclinata fencing posts against termite attack were assessed. The objectives were to determine (i) the incidence and (ii) severity of termite attack on Eucalyptus grandis × Eucalyptus camaldulensis and Phoenix reclinata fencing posts treated with Copper Chrome Arsenate or used engine oil. Ninety 2ft long samples of Eucalyptus grandis × Eucalyptus camaldulensis and P. reclinata posts were treated with Copper Chrome Arsenate or used engine and others left to act as control then buried in 1ft deep pits in the ground at a spacing of 1m by 1 in Eastern Uganda. The samples were visually inspected monthly for termite damage for 9 months. More than 80% of untreated samples of both species had been attacked by termites within the first month. Copper Chrome Arsenate treated Eucalyptus grandis × Eucalyptus camaldulensis and Phoenix reclinata samples were first attacked in the 8th and 5th months respectively. While used engine oil treated Eucalyptus grandis × Eucalyptus camaldulensis and Phoenix reclinata samples were first attacked in the 7thand 5th months respectively. The modal severity for samples of both species treated with either Copper Chrome Arsenate or used engine oil was class 1 (less than 1% of the sample volume eaten) while for the untreated samples it was class 5 (above 60% volume eaten) for the 9 months of field exposure. It was concluded that untreated posts of Eucalyptus grandis × Eucalyptus camaldulensis and Phoenix reclinata were highly susceptible to termite attack and that the protection offered by used engine oil or Copper Chrome Arsenate managed to restrict damage by termites to only less than 1% of the sample volume , over the 9 months of exposure for most of the sample posts. It is recommended that the experiment be repeated for a much longer period in order to ascertain the exact service life of the posts under these circumstances. Penetration and retentions of the preservatives in the posts should also be studied in order to ascertain their effect on the efficacy.

The upper cell layers of machined solid wood surfaces will usually be damaged and compacted due to cutting forces. The deformation zone may be instable due to temperature and moisture variations as a consequence of artificial surface treatment or environmental interaction. Therefore, an evaluation method of surface stability in this respect would be desirable. In the frame of the new developed surface roughness evaluation method an individual wetting procedure has been developed, whilst surfaces have been characterized by 3D roughness measurement. The stability of surfaces is characterized by appropriate roughness ratios measured before and after wetting. The core depth Sk of the Abbott parameters is the most sensitive indicator to any changes in the deformation zone. Different machining processes may produce surfaces with different stability but wood species have also definite influence on the surface stability, probably due to their density and moisture conduction properties. Latter is supported by the fact that the half-time of moisture evaporation from surfaces may differ considerably. In these experiments, planed and precision-planed surfaces were compared. According to the working principle of the precision planers the planing tool is held stationary whilst the work piece does the feeding motion, thus the blade produces a very thin slice. Using this machine, the machining roughness can be reduced to minimum as it is possible to avoid formation of cycloid arcs (like in case of traditional planing) and also possible to avoid dust formation (like in case of sanding). Investigations were conducted on Norway spruce (Picea abies), larch (Larix decidua), scots pine (Pinus sylvestris), sessile oak (Quercus petraea), black locust (Robinia pseudoacacia), aspen (Populus tremula) and beech (Fagus sylvatica). Black locust and the sessile oak  have had most stable surfaces by both machining methods. The deformation zone of precision planed surfaces has been proven to be more stable than the one of planed surfaces for all wood species.

Choice and no-choice tests were run to evaluate natural resistance of the woods of two Morus species (Morus alba and Morus nigra) against the subterranean, by Heterotermes indicola under field conditions. Toxicity, antifeedant and repellency potential of the heartwood extractives was also investigated under laboratory conditions. Heartwood extractives were removed from wood shavings by using methanol or an ethanol: toluene (2:1) mixture. Results of choice and no-choice tests with sap and heartwood blocks exposed to termites, showed that both mulberry species were resistant to termites but in comparison. Morus alba wood was more resistant than Morus nigra to termite feeding as it showed <5 % weight loss after 90 days. Termites exhibited a concentration dependent mortality after exposure to either mulberry species’ heartwood extractives. The highest termite mortality occurred after termites were exposed to filter paper treated with Morus alba extractives at a concentration of 5%. . At this concentration, antifeedancy and repellency were calculated to be 91.67 and 84 %respectively. . Our results also showed that extractives from either mulberry species imparted resistance to vacuum-pressure treated non-durable Populus deltoides wood. Termite mortality was greater than 75 % after feeding on Populus deltoides wood treated with extractives from Morus alba. Solvent only (methanol) treated Populus deltoides controls, showed a minimum weight loss of 2.69 % after 28 days. These results suggest that Morus alba extractives have antitermitic properties and may be potentially useful in the development of environment friendly termiticides.

Eucalyptus nitens is a fast growing plantation species that has a good acclimation in Chile. It is commonly used for pulp and paper, but there is a growing market for solid wood products made from this species and an interest on producing high quality material. Thermal modification technology have been used to obtain high quality product out of fast growing plantation species. In this study we modified Eucalyptus nitens to analyse the influences of the process conditions and evaluated its mechanical properties under several process conditions. The material was modified in a closed system under elevated pressure and controlled relative humidity (30 and 100% relative humidity) at temperatures between 150 and 170°C, and in an open system with a standard thermal modification procedure between 160 and 230°C. Modulus of elasticity, modulus of rupture, deflection and work in bending (in elastic and inelastic proportions) and the resistance to impact milling in high energy multiple impact tests were determined. Mass loss after each modification was also measured and correlated with the mechanical properties. Anatomical properties of selected modifications were analysed. There were no significant differences between open and closed system modifications in both mechanical and anatomical properties.

The effect of heat treatment at 50 and up to 150°C was studied on dowel-shape specimens prepared from beech (Fagus orientalis), poplar (Populus nigra), and fir (Abies alba) wood. Specimens were cut into two diameter sizes (18 and 25mm) to explore the effect of diameter size on permeability. Separate sets of specimens from each size and species were prepared to be first impregnated with a 200 ppm aqueous nanosilver (NS) suspension to investigate the effect of facilitated heat-transfer on permeability at different temperatures. Specimens were heated in five consecutive steps at 50, 75, 100, 125, and 150°C and for 24 hours in each step. High variance was found in the specific gas permeability between each treatment group, thus indicating probable high fluctuation in settlement of extractives at different spots of a log. Heat treatment only affected gas permeability at the first steps of heating (50 and 75°C), where loss of moisture content resulted in a permeability increase in nearly all species. Consecutive steps of heating up to 150°C did not significantly affect the permeability in either normal or NS-impregnated specimens.

The effect of low pressure saturated vapor pre-steaming on restrained shrinkage strain, mechano-sorptive creep and the distribution of moisture content was investigated during conventional drying of wood discs. Mechano-sorptive creep was furthermore modelled by artificial neural network theory with five inputs, i.e., pre-steaming and drying temperatures, wood moisture content, relative humidity and distance from the pith. Results revealed that, pre-steaming partly reduced the variation of moisture content distribution along radial direction, increased restrained shrinkage strain in heartwood and decreased in sapwood and slightly decreased the mechano-sorptive creep. The neural network model provided reasonable prediction results, namely, the coefficient of determination for training, validation and test sets greater than 0.95.

This study investigated the thermal properties of Oriental beech (Fagus orientalis) treated with (NH4)2HPO4, K2HPO4, NH4Cl and (NH4)2SO4 salts and their mixtures (1:1; w/w) aqueous solutions at 3% concentrations. The effects of different inorganic salts fire retardants on the thermal degradation characteristics of wood samples were evaluated by thermogravimetric analysis (TGA). Based on the TGA curve for untreated beech wood, weight loss takes place at three distinct steps. The impregnation of inorganic salts resulted in higher char yields and additional thermal degradation steps were identified. The highest char yield (80%) was obtained from (NH4)2HPO4-K2HPO4 mixture impregnated sample.  Salt mixtures containing phosphates ((NH4)2HPO4 and K2HPO4) have remarkable effects on thermal stability of beech wood, whereas NH4Cl salt lowered the decomposition temperatures and char yield.  

 In this paper result of working quality of Melia dubia was reported after testing them under six major wood working operations namely – planning, sanding, turning, shaping, boring and mortising based on Indian Standard IS 8292. The wood performed extremely well under planning. In shaping, the performance was good enough. Though all the other operations yielded poor results, the composite rating factor which is an overall performance indicator was 35 % more than that of Tectona grandis. The ease of working is only 93 % compared to teak. The working quality index which was based on the composite rating factor and ease of working worked out to 107 taking Tectona grandis as 100 mainly because of the high performance under planning and shaping and good performance under sanding.

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.