Physical Properties of Thermally Modified Juvenile and Mature Wood of <i>Hevea brasiliensis</i> (Euphorbiaceae)

Calonego, Fred Willians; Severo, Elias Taylor Durgante; Latorraca, João Vicente de Figueiredo; Bond, Brian H.

doi:10.1590/2179-8087.084117

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ORIGINAL ARTICLE, Wood Science and Technology • Floresta Ambient. 27 (2) • 2020 • https://doi.org/10.1590/2179-8087.084117 copy

Physical Properties of Thermally Modified Juvenile and Mature Wood of Hevea brasiliensis (Euphorbiaceae)

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Exposing timber to temperatures approaching 200 °C causes thermal modification and changes its characteristics. This study evaluates the effect of various levels of thermal treatment on the physical properties of juvenile and mature wood from rubber tree (Hevea brasiliensis). Boards taken from 53-year-old rubber trees were thermally modified at up to 220 °C. Thermal treatment caused decreases on the oven-dried density, equilibrium moisture content, and swellings on juvenile and mature woods of H. brasiliensis. Influence of thermal modification at 180-200 °C in juvenile wood was lower than in mature wood, whereas the treatment at 220 °C caused a greater variation in properties of juvenile wood. The thermally modified wood is a suitable product for use in environments with high levels of relative humidity.

Keywords:
thermal modification; rubber wood; maximum swellings; density of wood; equilibrium moisture content

		Temperature
Property	Untreated	180 °C	200 °C	220 °C
Oven-dried Density (g cm ^-3 )
Juvenile Wood, CV	4.5	4.1	2.1	4.4
Juvenile Wood, Mean	0.640 a	0.622 ab	0.631 ab	0.612 b
Juvenile Wood, ↓ (%)	-	−2.81	−1.41	−4.38
Mature Wood, CV	4.9	6.4	4.5	5.0
Mature Wood, Mean	0.638 a	0.628 ab	0.626 ab	0.614 b
Mature Wood, ↓ (%)	-	−1.57	−1.88	−3.76
↓ or ↑ (%)	−0.31^NS	0.97^NS	−0.79^NS	0.33^NS
Equilibrium Moisture Content at 21 °C and 65% RH (%)
Juvenile Wood, CV	1.8	4.0	3.2	7.6
Juvenile Wood, Mean	8.98 a	8.16 b	7.75 c	6.31 d
Juvenile Wood, ↓ (%)	-	−9.13	−13.70	−29.73
Mature Wood, CV	1.8	3.5	3.7	8.8
Mature Wood, Mean	9.23 a	8.30 b	7.81 c	6.80 d
Mature Wood, ↓ (%)	-	−10.08	−15.38	−26.33
↑ (%)	2.78 *	1.72 *	0.77^NS	7.77 *

		Temperature
Property	Untreated	180 °C	200 °C	220 °C
Maximum Volumetric Swelling (%)
Juvenile Wood, CV	6.0	10.1	9.0	13.1
Juvenile Wood, Mean	9.34 a	9.35 a	9.31 a	6.67 b
Juvenile Wood, ↓ or ↑ (%)	-	0.11	−0.32	−28.59
Mature Wood, CV	7.5	9.7	9.2	17.3
Mature Wood, Mean	9.55 a	9.12 a	8.88 a	7.77 b
Mature Wood, ↓ (%)	-	−4.50	−7.02	−18.64
↓ or ↑ (%)	2.25^NS	−2.46^NS	−4.62^NS	16.49 *
Maximum Tangential Swelling (%)
Juvenile Wood, CV	9.0	10.8	9.5	19.2
Juvenile Wood, Mean	5.56 a	5.74 a	5.61 a	4.34 b
Juvenile Wood, ↓ or ↑ (%)	-	3.24	0.90	−21.94
Mature Wood, CV	6.6	9.9	8.2	18.1
Mature Wood, Mean	6.05 a	5.99 a	5.84 a	4.90 b
Mature Wood, ↓ (%)	-	−0.99	−3.47	−19.01
↑ (%)	8.81 *	4.36 *	4.10 *	12.90 *
Maximum Radial Swelling (%)
Juvenile Wood, CV	23.7	23.6	22.3	11.9
Juvenile Wood, Mean	2.94 a	2.92 a	2.99 a	1.96 b
Juvenile Wood, ↓ or ↑ (%)	-	−0.68	1.70	−33.33
Mature Wood, CV	16.9	13.5	20.0	19.1
Mature Wood, Mean	2.80 a	2.52 a	2.51 a	2.42 a
Mature Wood, ↓ (%)	-	−10.00	−10.36	−13.57
↓ or ↑ (%)	−4.76^NS	−13.70 *	−16.05 *	23.45 *
Maximum Axial Swelling (%)
Juvenile Wood, CV	25.0	15.2	10.0	40.5
Juvenile Wood, Mean	0.62 a	0.47 b	0.49 b	0.27 c
Juvenile Wood, ↓ (%)	-	−24.19	−20.97	−56.45
Mature Wood, CV	15.3	17.5	25.1	26.1
Mature Wood, Mean	0.48 a	0.42 ab	0.35 bc	0.31 c
Mature Wood, ↓ (%)	-	−12.50	−27.08	−35.42
↓ (%)	−22.58 *	−10.64^NS	−28.57 *	14.81^NS

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[1] CORRESPONDENCE TO Fred Willians Calonego Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Av. Universitária, 3.780, Altos do Paraíso, CEP 18610-034, Botucatu, SP, Brasil e-mail: fwcalonego@gmail.com