Volume 11 Issue 4

There has been a strong recent effort to develop procedures that prevent the unnecessary replacement of timber utility poles. Even when assessments show that the utility pole needs to be replaced, there are many cases in which the removed utility poles can be reused. The aim of this study was to determine the mechanical properties of Maritime Pine (Pinus pinaster (Ait.)) utility poles removed from service (UPRFS) in order to assess their ability to be reused in structural applications. A sample of 51 UPRFS in Portugal was selected, and visual and mechanical properties were evaluated through non-destructive and destructive tests. Dynamic modulus of elasticity (MOEdyn) was correlated with bending strength (MOR) (r = 0.43) and modulus of elasticity (MOE) (r = 0.71). UPRFS showed a decrease of 14% and 6% in the mean values of MOR and MOE, respectively, when compared with new utility poles. A high variability and low values were obtained for MOR. These results highlight the reuse potential of the maritime pine utility poles for structural applications. Furthermore, the determined properties of UPRFS could be improved with a more stringent selection process that discards utility poles showing severe damage or by removing damaged areas in the utility poles.

Several works have analyzed the alteration in the mechanical strength of wood after the application of protective substances. However, it remains unclear whether the significant differences obtained are caused by the protective substances, the pressure and vacuum conditions used in the treatment, or the simultaneous effect of both. In this study, 123 wood samples from Pinus sylvestris were tested for bending, and 85 samples were tested for compression strength parallel to the grain. These samples were randomly distributed in three groups (treated with water pressure, water vacuum, and control samples simply submerged in water). The results indicated that there was no difference in mechanical properties between the treated and untreated samples. In contrast, significant differences were detected in equilibrium moisture after a prolonged drying process.

This study deals with the characteristics of wood of two different species of oaks, the non-native northern red oak (Quercus rubra L.) and the native pedunculate oak (Quercus robur L.), growing in a reclaimed surface brown coal mine in the Czech Republic. The differences in the wood density of the aforementioned species, including the impact of position in the trunk, were examined. The impact of annual ring width and the proportion of latewood on density were also evaluated. The density of Q. robur wood reached 707 kg·m-3, which was significantly higher than that of the North American species, which reached 654 kg·m-3. Moreover, in the radial direction, the density increased in the direction from the pith toward the bark for both Q. rubra, and Q. robur. In the vertical direction, the density reached its highest value at the basal part of the trunk, but statistically, this assertion was only significant for Q. rubra. The effects of annual ring width and the proportion of latewood on density were shown to be statistically very low for both oak species.

The goal of the study was to analyse of the stiffness of one-sided, asymmetrical veneered boards by investigating the influence of glue type and board thickness on deflection and stress distribution on each composite layer. A specially designed stand that measured the whole area of the board was used to empirically measure the asymmetrically veneered elements. The theoretical measurements were taken using the Finite Elements Method in the Autodesk Mechanical Simulation 2015® program. All elements of composites including veneer (beech), glue-line (polyisocyanate and poly (vinyl acetate)), and the wood-based panel were simulated as elastic materials.

The behavior of paulownia wood (Paulownia elongata) was investigated using three different ageing tests: simulated natural ageing under the influence of light under indoor conditions, temperature-induced ageing in the dark, and UV-induced ageing. Ageing effects were evaluated by color measurements in the CIE Lab system. Simulated natural ageing of wood in indoor conditions (6 months) and UV-accelerated ageing (72 h) are complex and dynamic processes, which resulted mostly in yellowing of the samples due to photo-degradation. Temperature-induced ageing (288 h at 100 C) resulted mostly in a rapid and visible darkening of the paulownia wood. Comparative in-time evolution of color changes during accelerated UV ageing testing and simulated natural ageing testing under indoor conditions allowed the estimation of an acceleration index of about 50X. Fourier transform infrared spectroscopy (FTIR) was used to examine specific chemistry changes occurring during these ageing tests. UV light from natural or artificial sources caused primarily lignin degradation followed by oxidative processes leading to carbonyl-containing chromophores. Temperature-induced partial degradation of hemicelluloses and oxidative processes resulted in the formation of chromophores containing mostly conjugated carbonyl groups. This research highlighted that paulownia wood (P. elongata) is quite sensitive to ageing under the action of light and temperature, which cause notable color and surface chemistry changes.

Eulaliopsis binata (EB) was pretreated by continuous screw extrusion steam explosion (SESE), with the aim of converting EB into useful materials on an industrial scale. The three main chemical components were characterized by component analysis using the Van Soest fiber detergent system, ultraviolet (UV) absorption spectrophotometry, gel permeation chromatography (GPC), and carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy. Changes in the contents of detergent soluble species in the Van Soest process revealed the partial degradation of hemicellulose and cellulose, and the partial removal of lignin. GPC indicated that the molecular weight of lignin decreased from 4194 to 3710 g/mol over the first three SESE pretreatment cycles, but then increased to 4592 g/mol following the fourth SESE pretreatment cycle. UV absorption and 13C-NMR results indicated the partial removal of lignin and the depolymerization and repolymerization of lignin during SESE pretreatment. Scanning electron microscopy (SEM) showed that the epidermis and parenchyma of EB were almost completely desquamated. X-ray diffraction (XRD) revealed that the crystallinity of EB initially increased and then subsequently decreased slightly, with increasing number of SESE pretreatment cycles. The varying physicochemical properties of EB resulting from different numbers of pretreatment cycles may find use in more diverse applications.