André Luiz Missio

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.

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.

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.

Prediction of the modulus of elasticity of Eucalyptus grandis through two nondestructive techniques

The present study aimed to estimate the modulus of elasticity (MOE) at static bending of Rose gum (Eucalyptus grandis) heartwood and sapwood through two nondestructive techniques: ultrasound and stress wave. Sixty samples of heartwood and sapwood were prepared. Nondestructive tests were performed using ultrasound and stress wave timer equipment, while destructive tests were carried out in a universal machine through static bending tests. The main results showed that the heartwood presented better behavior than the sapwood in the non-destructive tests. However, the best model was obtained considering both wood types through the ultrasonic technique. Therefore, stress wave and ultrasonic techniques could be employed to estimate the modulus of elasticity of Rose gum wood.

Método ultrassônico para estimativa do módulo de elasticidade de madeiras de Pinus taeda tratadas termicamente

This study aimed to estimate the modulus of elasticity of Pinus taeda thermally modified wood by ultrasonic nondestructive method. To achieve this, 93 samples with dimensions 2.5x2.5x41.0cm (thickness, width and length) from pine boards were prepared. The wood samples were thermally modified through two distinct treatments (Combination and Oven). The Combination treatment was performed in an autoclave at 130oC±3°C and pressure of 2kgf cm-2 for 3 hours. After a period of conditioning, the wood samples were heated in an electric oven 160°C±1°C for the same time. On the other hand, wood samples of the Oven treatment was modified with only last condition. The mathematical models showed r2 between 0.48 and 0.66 and significance at 1% of probability of error. Thus, improvement of ultrasonic nondestructive tests shows that technique could be useful and efficient in order to estimate modulus of elasticity of Pinus taeda wood.

Decay resistance of four fast-growing Eucalypts wood exposed to three types of fields

The evaluation of wood durability enables the definition of reliable parameters to predict the servicelife of wood-based products. This study aimed to evaluate the wood deterioration of four fast-growing eucalypts species (Eucalyptus botryoides, Corymbia citriodora, Eucalyptus paniculata e Eucalyptustereticornis) exposed to three field tests (outdoor, flooded site and forest canopy) during 540 days. The physical properties measured were: mass loss, density and moisture content. Furthermore, we determined changes in wood color by CIEL*a*b* method and performed a visual analysis by CENgrades. Among the four wood eucalypts, Eucalyptus tereticornis presented the highest decay resistance. The flooded site presented the best conditions for the proliferation of xylophagous agents. Mature wood was least susceptible to deterioration than juvenile wood.

Color changes of wood from Pinus taeda and Schizolobium parahybum treated by in situ polymerization of methyl methacrylate using cross-linkers

The aim of this study was to evaluate the colorimetric properties of Pinus taeda and Schizolobium parahybum woods treated by in situ polymerization. The wood samples were impregnated in a vacuum/ pressure system and polymerized in an oven at 90°C for 10h, using benzoyl peroxide at 1,5wt% as the catalyst. The treatments were characterized using attenuated total reflectance infrared (ATRIR) spectroscopy and weight percentage gain (WPG). The color evaluation was performed using CIEL*a*b* concepts, specular gloss, and UV-Visible spectrophotometry. Treated woods showed increases in band intensity related to polymers (1730, 1460 and 1145 cm-1), and WPG ranged from 39 to 164%, depending of the wood species and treatments. Lightness decreased, while the Chroma, gloss and the color coordinates increased. A darkening of the all treated samples was observed, and confirmed by the decrease in the reflectance intensity between 400 and 700 nm.

Effects of Two-Step Freezing-Heat Treatments on Japanese Raisintree (Hovenia Dulcis Thunb.) Wood Properties

In this study, we investigated the effects of two-step freezing-heat treatments on the technological properties of Japanese Raisintree (Hovenia dulcis Thunb.) wood. Three treatments were performed and compared to an untreated control: freezing (WF), freezing followed by heat (WFT), and heat treatment (WT). The freezing treatment and the heat treatment were performed at -22°C for 24 h and 180°C for 3.5 h, respectively. Chemical composition was evaluated by TAPPI standards and ATR-IR; physical changes were investigated with dimensional stability and water uptake tests, while mechanical properties were evaluated by impact strength. Color and roughness tests were also performed. The main results showed no significant changes to the chemical structure of the wood. Dimensional stability and water repellence increased up to 14% after the thermal treatments. On the other hand, maximum impact strength decreased significantly, especially in the WT treatment (∼50%). Lightness (L*) was the colorimetric parameter most affected by the thermal treatments, mainly in the treatments with a heating step. Surface roughness remained stable after thermal treatments.