Bruno D. Mattos

Colour changes of Brazilian eucalypts wood by natural weathering

Abstract This study aimed to characterise wood discolouration of three Brazilian eucalypt species exposed to the action of natural weathering in two distinct places. To achieve this, tests were performed at an exposed outdoor site and under a forest canopy; both located in the state of Rio Grande do Sul, Brazil. Colorimetric measurements were performed every 45 days during the period of 1 year in order to obtain the parameters L*, a*, b*, C* and h*. The main results showed significant darkening in the first 4 months and subsequently increased the greyish colour. Colour variations were observed between species, field and exposure time in service.

Controlled release for crop and wood protection: Recent progress toward sustainable and safe nanostructured biocidal systems

We review biocide delivery systems (BDS), which are designed to deter or control harmful organisms that damage agricultural crops, forests and forest products. This is a timely topic, given the growing socio-economical concerns that have motivated major developments in sustainable BDS. Associated designs aim at improving or replacing traditional systems, which often consist of biocides with extreme behavior as far as their solubility in water. This includes those that compromise or pollute soil and water (highly soluble or volatile biocides) or those that present low bioavailability (poorly soluble biocides). Major breakthroughs are sought to mitigate or eliminate consequential environmental and health impacts in agriculture and silviculture. Here, we consider the most important BDS vehicles or carriers, their synthesis, the environmental impact of their constituents and interactions with the active components together with the factors that affect their rates of release such as environmental factors and interaction of BDS with the crops or forest products. We put in perspective the state-of-the-art nanostructured carriers for controlled release, which need to address many of the challenges that exist in the application of BDS.

Physical and mechanical properties and colour changes of fast-growing Gympie messmate wood subjected to two-step steam-heat treatments

Abstract This study aimed to evaluate physical and mechanical properties and colour changes of fast-growing Gympie messmate wood subjected to two-step steam-heat treatments. To achieve this, Gympie messmate wood was thermally treated under different conditions. Combined steam (127°C and ∼0,1471 MPa) and heat treatments in an oven (180–240°C for 4 hours) were performed. Physical and mechanical properties were evaluated by weight loss, equilibrium moisture content, specific gravity, volumetric and linear swelling and static bending tests, while colour changes were studied using CIEL*a*b* technique. The main findings showed that the steam pre-treatment in autoclave influenced most of the technological properties evaluated, mainly for heat treatments performed in low temperatures (180–200°C). The most significant changes after thermal treatments were observed for dimensional stability, which increased as a function of temperature of treatment. On the other hand, mechanical strength of thermally modified wood was significantly affected, while stiffness did not change. Colour modifications due to the application of two-step steam-heat treatments confirm the possibility to using these samples for aesthetic purposes.

Desempenho silvicultural e seleção precoce de clones de híbridos de eucalipto

The objective of this work was to evaluate the genetic variability and silvicultural performance of clones from interspecific hybrids of Eucalyptus urophylla, E. globulus, E. maidenii, E. saligna, E. grandis, E. pellita, E. resinifera, E. kirtoniana and E. dunnii, and to determine the feasibility of early selection in selecting superior clones. The stem diameter at breast height at three (DAP3) and seven years (DAP7) and the total tree height at seven years were evaluated. A randomized complete block design, with138 clones, ten replicates and six plants per plot was used. Data were subjected to analysis of variance and clustered by the k-means method; the means were compared, and the Pearson correlation (r) was determined between variables. Clustering validation was performed using analysis of variance and Tukeys test. Clones of interspecific Eucalyptus hybrids showed genetic variability. Five groups of clones were established based on their silvicultural performance (DAP3, DAP7 and height). The DAP3 is highly correlated to DAP7 and height at seven years. The selection based on DAP3 can be used to identify superior clones of Eucalyptus with good growth vigor.

Thermal Analysis of Charcoal from Fast-Growing Eucalypt Wood: Influence of Raw Material Moisture Content

Abstract This study aimed to investigate the influence of raw material moisture content on the properties of charcoal from fast-growing Eucalyptus benthamii wood. For that, three treatments were performed with 0, 30, and 50% in relation to the wet basis moisture of the wood samples. The carbonization process used an electric kiln with a heating rate of 1.60°C min−1, initial temperature of 25 to 600°C at the end, kept constant at that temperature for two hours. Variables were statistically analyzed for charcoal yield, non-condensable gases, liquor, and fixed carbon and properties: fixed carbon content, volatile, ash, bulk density, and moisture content of charcoal. According to the results, the charcoal produced from dry wood presented the highest properties, yet the charcoal produced from wood with 30% moisture content showed similar properties.

Resistência ao impacto da madeira de nogueira-pecã em diferentes condições de umidade

The studies of wood impact strength refers to the efficiency of this material in absorb impact energy and dissipate it without structural damages. The present study aimed to evaluate the influence of moisture content on the impact strength of nogueira-peca (Carya illinoinensis) wood. For this, trees from two physiographic regions of state of Rio Grande do Sul were used. The samples, stabilized at 12% of moisture content and in green conditions (saturated), were submitted to impact tests through a CHARPY pendulum, and were evaluated for the resistance to the application of loads in the tangential and radial sections, and in the positions of the log (pith-bark) for the two physiographic regions at each moisture condition. Moreover, the apparent specific gravity at 12% and in green conditions (saturated), the absorbed work, the resilience coefficient and the dynamic quote were determined. The main results showed that the nogueira-peca wood is more resistant to the impact when it is in green conditions.

Natural weathering performance of three fast-growing Eucalypt woods

We investigated the effect of outdoor exposure on the wood surface from three fast-growing Brazilian eucalypts through color, wetting and thermal analyzes. Gympie messmate (Eucalyptus cloeziana), rose gum (Eucalyptus grandis) and blue gum (Eucalyptus saligna) woods were exposed outdoors in a subtropical region for 360 days. We performed three collections every 120 days. We investigated color changes of untreated and weathered woods through a spectrophotometer (CIEL*a*b* system) and changes in macro compounds of wood through thermogravimetric analysis. In addition, the apparent contact angle and work of adhesion were evaluated using a goniometer. Outdoor exposure for 120 days provided significant increment in grayish of wood surface. Thermogravimetric curves of wood changed after the weathering, especially in the regions related to hemicelluloses and lignin thermal degradation. Outdoor exposure for 360 days converted hydrophilic wood surface into a very hydrophilic one, wherein occurrence of microcracks contributed to fully spreading of water droplets.

Effect of thermal treatments on technological properties of wood from two Eucalyptus species

The effect of thermal treatments on physical and mechanical properties of rose gum and Sydney blue gum wood was evaluated. Wood samples were thermally modified in a combination: pre-treatment in an autoclave (127°C - 1h) and treatment in an oven (180-240°C - 4h); and only treatment in an oven at 180-240°C for 4h. Chemical changes in the structure of woods were evaluated through infrared spectroscopy. Evaluation of physical properties was performed through mass loss, specific gravity, equilibrium moisture content and dimensional stability tests. Surface changes were analyzed through apparent contact angle technique and static bending tests were carried out to evaluate the mechanical behavior. Use of pre-treatment in autoclave affected the properties analyzed, however oven, resulted in the highest changes on wood from both species. Chemical changes were related to the degradation of hemicelluloses. Moreover, a significant decrease of hygroscopicity and mechanical strength of thermally modified woods was observed, while specific gravity did not significantly change for either of the species studied. The best results of decrease of wettability were found in low temperatures, while dimensional stability increased as a function of temperature of exposure in oven. The highest loss of mechanical strength was observed at 240°C for both species.

Colour responses of two fast-growing hardwoods to two-step steam-heat treatments

Colour changes by thermal treatments are a good alternative to increase wood quality, especially for non-structural uses. In this study, rose gum (Eucalyptus grandis) and Sydney blue gum (Eucalyptus saligna) woods from Southern Brazil were thermally treated under different conditions (steam pretreatment in an autoclave at 127 °C for 1 hour and heat treatment in an oven at 180, 200, 200 and 240 °C for 4 hours) and colour changes were investigated using CIEL*a*b* technique. The main findings show that thermal treatments resulted in darkening of the wood, which was more intense at high temperatures. Colour difference after two-step steam-heat treatments was higher than 45 for both species. In general, the influence of the steam pre-treatment was more visible in lower temperatures. Lightness (L*) was the parameter that best described the colorimetric behaviour of rose gum and Sydney blue gum woods. In conclusion, thermal treatments are a great method to improve the market value of wood, especially for aesthetic uses, but it requires a control of process conditions.

Estimativa da deterioração da madeira de assoalho de prédio histórico por meio de ondas ultrassônicas

This study aimed to detect the external degree of decay of Araucaria angustifolia (Bert.) O. Kuntze wood used in flooring. The visual method through grades and the non-destructive method based on the propagation of ultrasound waves were applied. The comparison between the propagation velocity of ultrasonic waves on clear wood and decayed wood showed statistical difference at the 5% level. Moreover, the proportion of decay wood was inversely proportional to the velocity of propagation. The samples were evaluated only on their superficial faces, therefore additional studies to assess the influence of the wood internal defects in the ultrasonic velocity are necessary.