Latex is the main product extracted from rubber tree (Hevea brasiliensis). In Brazil, at the end
of the production cycle of latex, rubber wood is traditionally used for energy purposes but
international studies have reported consolidated practice that result in added-value products.
Several researchers have observed raised and worsening of tapping panel dryness, a disease
that impairs the production of latex. The main objective of this study was to evaluate the
quality of rubber wood of commercial clones GT 1 and RRIM 600 in three distinct health
conditions: trees producing latex (healthy), trees with tapping panel dryness of
abiotic/physiological origin and trees with tapping panel dryness of biotic/pathological origin.
Six trees of each health condition of the two clones from plantations in the São José do Rio
Preto region – Sao Paulo State, Brazil - aged 20 years or more were sampled. Anatomical and
physical-mechanical parameters evaluated were fibers length (occurrence and delimitation
juvenile–mature wood), specific gravity and apparent density, shrinkage and anisotropy index,
compression parallel to grain strength, bending strength and rigidity and Janka hardness.
Results showed that juvenile wood occurs from pith up to 40% and 32% of ray for GT 1 and
RRIM 600 clones respectively, allowing the association of the age of 6 to 8 years of plantation
as transition between juvenile and mature wood. The mean specific gravity of rubber wood
from both clones varied from 580 kg/m3 to 595 kg/m3 and there wasn’t statistical difference of
this parameter among health conditions and between clones. Rubber wood apparent density
from both clones presented four preferential patterns of radial variation. The most common pattern (occurrence of 60.5%) revealed initial decrease from pith to bark, with posterior
increase and eventual variations in the outer trunk. Wood from both clones was classified as
low shrinkage wood and juvenility affect shrinkage properties. GT 1 clone presented
compression parallel to grain strength ranging from 41.55 MPa to 48.22 MPa and for RRIM
600 clone this variation was from 34.96 MPa to 47.89 MPa. In bending test, GT 1 clone
presented strength and rigidity from 79.67 MPa to 90.98 MPa and from 9,353 MPa to
10,863 MPa, respectively. For RRIM 600 clone these properties ranged from 61.05 MPa to
94.11 MPa and from 7,138 MPa to 11,579 MPa. Janka hardness ranged from 57.27 MPa to
73.71 MPa for GT 1 clone and from 50.03 MPa to 84.92 MPa for RRIM 600 clone. The effect
of juvenility in mechanical properties was very discreet, been observed only in Janka
hardness. Overall there wasn’t statistical difference of mechanical properties in relation to
three trees health conditions. Considering these results for this study conditions rubber wood
had constant quality in the radial direction, revealing equivalent technological potential in
three tree health conditions studied.
