scholarly journals Effect of thermo-hydro-mechanical densification on the wood properties of three short-rotation forest species in Costa Rica

BioResources ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. 8065-8084
Author(s):  
Carolina Tenorio ◽  
Roger Moya
Keyword(s):  
Costa Rica ◽  
Color Change ◽  
Initial Density ◽  
Maximum Load ◽  
Wood Properties ◽  
Modulus Of Rupture ◽  
Densified Wood ◽  
Normal Wood ◽  
Densification Process ◽  
Short Rotation

Alnus acuminata, Vochysia ferruginea, and Vochysia guatemalensis are three low-density wood species used for reforestation in Costa Rica. The goal of this work was to study a thermo-hydro-mechanical densification process and test the characteristics of densified wood of these species. Twelve densifying treatments based on temperature, compression time, and use/no use of steam were tested. The variables of the densification process and the properties of the densified wood were determined. The results showed that the densification percentage was over 80% for wood of A. acuminata and over 70% for wood of V. ferruginea and V. guatemalensis. In the three species, the densification process was influenced by initial density. The influence of temperature during the densification process affected the heating rate and color change. An increase in the modulus of elasticity and modulus of rupture in static bending and in the hardness of the densified wood relative to the normal wood was observed, as well as a clear positive correlation of the properties with final density and maximum load, the latter being highly correlated with initial density. This showed that initial density was significant in the densification process and affects wood properties.

scholarly journals Effect of Moderate Temperature Thermal Modification Combined with Wax Impregnation on Wood Properties

2020 ◽  
Vol 10 (22) ◽  
pp. 8231
Author(s):  
Jing-Wen Zhang ◽  
Hong-Hai Liu ◽  
Lin Yang ◽  
Tian-Qi Han ◽  
Qin Yin
Keyword(s):  
Mechanical Strength ◽  
Dimensional Stability ◽  
Color Change ◽  
Strength Loss ◽  
Wood Properties ◽  
Thermal Modification ◽  
Moderate Temperature ◽  
Modulus Of Rupture ◽  
Internal Surfaces ◽  
Higher Temperature

Thermal modification (TM) improves the hydrophobicity, dimensional stability, and durability of wood, but TM commonly results in severe color change and mechanical strength loss as wood is treated at higher temperature. In this study, Pterocarpus macrocarpus Kurz wood was thermally modified at moderate temperature (150 °C) and higher temperature (200 °C), and subsequently TM wood at 150 °C was subjected to wax impregnation (WI), the effect of a combination of TM and WI on the hygroscopicity, dimensional stability, and mechanical properties, as well as the micro-structure of wood, were investigated and compared. The results showed that the mass loss of wood was slight at 150 °C TM, while it became severe at 200 °C TM conditions. TM conditions affected the amount of the subsequent wax impregnation; the equilibrium moisture content (EMC), water absorption ratio, and adsorption and absorption swelling of the 150 °C TM + WI group were lower than that of 200 °C TM, and presented the lowest value. Moderate temperature TM could improve the hydrophobicity and dimensional stability of wood, but WI played a key role in the improvement. TM decreased the modulus of rupture (MOR) of wood, while WI improved the MOR. TM increased the modulus of elasticity (MOE) of wood, but WI had little effect on MOE; Scanning electron microscope (SEM) observation showed that the wax was successfully impregnated into the wood interior, and presented an even distribution on the internal surfaces of wood cells; Fourier-transform infrared spectroscopy (FTIR) spectra verified the changes of –OH and C=O after TM and TM + WI, which contributed to decreasing hygroscopicity and improving the dimensional stability of the wood. Impregnated wax improved wood mechanical strength, but decreased the lightness, and deepened the color of wood. The combination of thermal modification at moderate temperature with subsequent wax impregnation is a practical approach for improving wood properties.

Effect of CaCO3 on the wood properties of tropical hardwood species from fast-growth plantation in Costa Rica

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 4802-4822
Author(s):  
Roger Moya ◽  
Johanna Gaitán-Álvarez ◽  
Alexander Berrocal ◽  
Fabio Araya
Keyword(s):  
Costa Rica ◽  
Dimensional Stability ◽  
Exchange Process ◽  
Untreated Wood ◽  
Physical And Mechanical Properties ◽  
Wood Properties ◽  
Decay Resistance ◽  
Modulus Of Rupture ◽  
Solution Exchange ◽  
Hardwood Species

This work aimed to evaluate the effect of the precipitation of CaCO3 via subsequential in-situ mineral formation based on a solution-exchange process of two solution-exchange cycles via impregnation with CaCl2 in ethanol and NaHCO3 in water. The effects were investigated in terms of the structure of the wood and the thermal, physical, mechanical, and decay resistance properties of nine species commonly used in commercial reforestation in Costa Rica. The thermogravimetric analysis results showed that the woods with the highest formation of CaCO3 showed a more pronounced signal at 200 °C in relation to untreated/wood; therefore, they were more thermostable. The fire-retardancy test showed that flame time in CaCO3/wood composites was longer than for untreated/wood in half of the species tested, presenting a positive effect of mineralization. Wood density, decay resistance, modulus of rupture (MOR), modulus of elasticity (MOE) in flexion, and MOR in compression were slightly affected by mineralization. Water absorption increased, but it had no negative effect on the dimensional stability. In general, mineralization can be a chemical treatment to increase the dimensional stability and fire resistance of hardwood species without modifying the wood’s physical and mechanical properties.

scholarly journals Evaluation of wood properties from six native species of forest plantations in Costa Rica

2016 ◽  
Vol 37 (1) ◽  
pp. 71-84 ◽  
Author(s):  
Carolina Tenorio ◽  
Róger Moya ◽  
Cynthia Salas ◽  
Alexander Berrocal
Keyword(s):  
Costa Rica ◽  
Native Species ◽  
Wood Properties ◽  
Forest Plantations

Estimation of Eucalyptus delegatensis wood properties by near infrared spectroscopy

2001 ◽  
Vol 31 (10) ◽  
pp. 1671-1675 ◽  
Author(s):  
L R Schimleck ◽  
R Evans ◽  
J Ilic
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Microfibril Angle ◽  
Nir Spectroscopy ◽  
Wood Properties ◽  
Raw Material ◽  
Modulus Of Rupture ◽  
Single Type ◽  
Wide Range ◽  
Eucalyptus Delegatensis

The use of calibrated near infrared (NIR) spectroscopy for the prediction of a range solid wood properties is described. The methods developed are applicable to large-scale nondestructive forest resource assessment and to tree breeding and silvicultural programs. A series of Eucalyptus delegatensis R.T. Baker (alpine ash) samples were characterized in terms of density, longitudinal modulus of elasticity (EL), microfibril angle (MFA), and modulus of rupture (MOR). NIR spectra were obtained from the radial–longitudinal face of each sample and used to generate calibrations for the measured physical properties. The relationships were good in all cases, with coefficients of determination ranging from 0.77 for MOR through 0.90 for EL to 0.93 for stick density. In view of the rapidly expanding range of applications for this technique, it is concluded that appropriately calibrated NIR spectroscopy could form the basis of a "universal" testing instrument capable of predicting a wide range of product properties from a single type of spectrum obtained from the product or from the raw material.

The effect of ionic liquid and superbase pre-treatment on the spring-back, set-recovery and Brinell hardness of surface-densified Scots pine

Holzforschung ◽  
2020 ◽  
Vol 74 (3) ◽  
pp. 303-312 ◽  
Author(s):  
Benedikt Neyses ◽  
Olov Karlsson ◽  
Dick Sandberg
Keyword(s):  
Ionic Liquid ◽  
Scots Pine ◽  
Brinell Hardness ◽  
Wood Products ◽  
Densified Wood ◽  
Crystalline Cellulose ◽  
Control Group ◽  
Densification Process ◽  
Spring Back ◽  
Pre Treatment

AbstractCompressing the surface of sawn timber results in a substantial increase in hardness, and this opens up new market opportunities of using low-density timber species as the raw material for high-value wood products. Unfortunately, widespread commercialisation is hindered by the lack of an industrially viable surface densification process, the major obstacle being the set-recovery (SR) of the densified wood cells upon exposure to moisture. Our hypothesis is that partial dissolution of the crystalline cellulose during densification will largely prevent the SR of densified wood. We therefore evaluated the effect of ionic liquid (IL) or organic superbase pre-treatment on the elastic spring-back (SB), SR and Brinell hardness (HB) of surface-densified wood. Specimens of Scots pine were treated with solutions of ILs or superbases, and then densified in a hot press at temperatures between 200°C and 270°C. The SR was reduced from 90% for the control group to only about 10% for the treated materials. The treated and densified specimens exhibited a higher HB than their untreated and densified counterparts. The method presented in this study is a precursor to the development of a continuous densification process adapted for an open system. Further studies are needed to understand the underlying mechanisms of the pre-treatment.

scholarly journals WOOD CHARACTERIZATION OF ADULT CLONES OF TECTONA GRANDIS GROWING IN COSTA RICA

CERNE ◽  
2015 ◽  
Vol 21 (3) ◽  
pp. 353-362 ◽  
Author(s):  
Natalia Arce ◽  
Roger Moya
Keyword(s):  
Costa Rica ◽  
Physical Properties ◽  
Color Change ◽  
Wood Quality ◽  
Tectona Grandis ◽  
End User ◽  
Wood Color ◽  
Commercial Market ◽  
Aesthetic Characteristics

ABSTRACT Tectona grandis is an important wood in the commercial market due to its excellent workability, durability and aesthetic characteristics. Therefore, it is important to improve the conditions of reproduction and development in commercial plantations using clone reproduction, in order to produce trees with better wood quality. In this study we analyzed the general properties, physical properties and color of 20 adult teak clones (fifteen-year-old) from the area of Guanacaste, Costa Rica. It was found that at 15 years, the clones have a diameter which varies from 19.82 cm to 30.13 cm, the percentage of heartwood ranges from 49.76 to 60.02%, and that these values are similar to those found in the literature. In regards to the physical properties, it was found that the specific gravity ranges from 0.45 to 0.60 g.cm-3, the green moisture content varies from 70% to 110.6%. In the color properties, it was found that L* values ranged from 48 to 59, a* 7 to 9.5 and b * from 20.5 to 26.3. Likewise it was determined that the color change (ΔE*) compared to commercial wood color, is commonly categorized as perceptible in all clones. However, three of the clones studied have a darker color and reddish wood which indicates a color more desirable to the end user.

scholarly journals Comparison of Methods for Estimating Mechanical Properties of Wood by NIR Spectroscopy

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
L. R. Schimleck ◽  
J. L. M. Matos ◽  
R. Trianoski ◽  
J. G. Prata
Keyword(s):  
Large Scale ◽  
Fiber Optic ◽  
Wood Property ◽  
Practical Interest ◽  
Nir Spectroscopy ◽  
Wood Properties ◽  
Modulus Of Rupture ◽  
Fiber Optic Probe ◽  
Optic Probe ◽  
Pine Species

Near-infrared (NIR) spectroscopy provides a rapid alternative to traditional methods of wood property assessment. For organizations who assess wood properties on a large scale, multisite, multispecies calibrations are of practical interest. We examined NIR spectroscopy for the estimation of density (at 12% moisture content), modulus of elasticity (MOE), and modulus of rupture (MOR) using clear wood samples obtained from several pine species (Pinus caribaeavar. bahamensis, var.hondurensis, and var. caribaea, P.chiapensis,P.maximinoi,P.oocarpa,P.taeda, andP.tecunumanii). We compared different methodologies for collecting spectra, that is, benchtop instrument versus benchtop fiber-optic probe and field portable fiber-optic probe, and different wood surfaces (radial and transverse). Calibrations based on the benchtop instrument were superior to those obtained using the fiber-optic probe systems. Difficulty with adequately representing the sample when collecting spectra using a fiber-optic probe and lower quality spectra explain the differences among the data sets. Spectra collected from radial and transverse surfaces provided similar calibration statistics. The calibrations obtained for density (R2 = 0.81, SECV = 38.5 kg/m3) and MOE (R2 = 0.81, SECV = 1124 GPa) using benchtop instrument spectra demonstrate that it is possible to obtain general calibrations for estimating the wood properties of a number of tropical, subtropical, and temperate pine species.

scholarly journals Temperature’s effect on color change and mechanical properties of poplar powder compact formed by warm compaction

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 7009-7017
Author(s):  
Liqiang Zhang ◽  
Zhizhong Long ◽  
Zhili Tan ◽  
Qingding Wu
Keyword(s):  
Mechanical Properties ◽  
Color Change ◽  
Chemical Properties ◽  
Added Value ◽  
Modulus Of Rupture ◽  
Surface Color ◽  
Warm Compaction ◽  
Infrared Spectral ◽  
Forming Temperature ◽  
Color Control

Warm compaction technology is an eco-friendly method to improve the added value of poplar. In this work, the wood powder was compacted in the mold between 120 °C to 200 °C, at 80 MPa for 30 min. The color change, chemical properties, and mechanical properties were evaluated. The color of the formed compaction darkened uniformly. The CIE lightness color coordinate (L*) and chroma coordinates a* and b* decreased with the increase of forming temperature. Fourier infrared spectral analysis showed degradation of carbohydrates, along with the formation of a new chemical structure of darker color. Mechanical properties including modulus of rupture (MOR) and modulus of elasticity (MOE) of compacted wood increased initially and then decreased. These results provide a reference for the surface color control of thermally forming materials.

scholarly journals Effect of Glue Spreads on the Structural Properties of Laminated Veneer Lumber from Spindleless Rotary Veneers Recovered from Short Rotation Hevea Plantation Logs

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3799
Author(s):  
Pui San Khoo ◽  
Kit Ling Chin ◽  
Chuan Li Lee ◽  
Paik San H’ng ◽  
Mohd Sahfani Hafizuddin
Keyword(s):  
Mechanical Properties ◽  
Small Diameter ◽  
Physical And Mechanical Properties ◽  
Longitudinal Axis ◽  
Modulus Of Rupture ◽  
Spread Rate ◽  
Minimum Requirement ◽  
Laminated Veneer Lumber ◽  
Short Rotation ◽  
Laminated Panels

Unproductive young rubber trees (15 years old) with smaller diameters (15 to 18 cm) compared to conventional rubber logs, harvested at the age of 25 years old, were selected for the production of laminated panels. Spindleless rotary veneer peeling was applied to logs from short-rotation rubber forest plantations to produce veneers for structural purposes. This raises questions about the utilization of these small-diameter logs with respect to its effect on the quality of veneer and laminated panels produced. This study examines the effect of the glue spread rates on the physical and mechanical properties of rubberwood laminated veneer lumber (LVL). Analysis of variance shows that the application of a 280 g/m2 glue spread rate significantly improved the density, water absorption and dimensional stability of rubberwood LVL. The mechanical properties of rubberwood LVL produced with a 200 g/m2 glue spread rate met the minimum requirement for the 2.1E-3100F stress class; 91.05 MPa for the modulus of rupture in the flatwise direction and 50.23 MPa for compressive strength parallel to the longitudinal axis. The modulus of elasticity in the flatwise direction of 11,189.55 MPa reached the minimum requirement for the 1.5E-2250F stress class.

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