The cultivation of rubber tree has been settled in as a profitable and sustainable activity, with a
significant growth in planted areas in Brazil. Established with the main objective of production
of latex, rubber tree plantations have, at the end of this cycle, good prospects as suppliers of
raw material for the segment of solid wood products. Previous studies have shown the
technical viability for log lamination (hot and cold processes) of Hevea brasiliensis, for
plywood production, as an option of higher added value product. This study evaluated
physical and mechanical performance of plywood of Hevea brasiliensis (clone RRIM 600)
made with graded veneers (stress wave method) in stiffness classes (low, medium and high
dynamic modulus of elasticity). Mechanical evaluations were conducted on plywood made
with nine 2.3mm thick veneers, produced in the Indústria de Compensados Caribea Ltda, in
São Manuel, São Paulo - Brazil. Plywood were made using the same equipment and general
variables of the manufacturing process adopted by this industry, considering five
arrangements: T1 – homogeneous low (plywood produced with only low dynamic modulus of
elasticity veneers); T2 – combined low (plywood produced with high dynamic modulus of
elasticity veneers in the face and back and low dynamic modulus of elasticity veneers in the
inner); T3 – alternate (plywood produced with alternated quality veneers - high and low
modulus of elasticity); T4 – homogeneous medium (plywood produced with only medium
dynamic modulus of elasticity veneers); T5 – combined medium (plywood produced with high
dynamic modulus of elasticity veneers in the face and back and medium dynamic modulus of elasticity veneers in the inner). Physical and mechanical performance of plywood was
evaluated by static bending, bond strength in shear (by tension load), moisture content, water
absorption, thickness swelling and density tests, performed using the ABNT – Associação
Brasileira de Normas Técnicas – standards for plywood. Considering that all arrangements
studied showed very good physical and mechanical performance, major conclusion is that the
equipment and variables used were appropriate for rubber wood plywood manufacture. The
average lamination yield was 39.9%, when considering the volume of green veneers in
relation to the logs with bark, and 44.9% when considering logs without bark; losses in the
lamination process were compatible with those routinely observed in the plywood industry. It
was possible to grade veneers in distinct modulus of elasticity classes using non-destructive
stress wave method, resulting modulus of elasticity ranging from 4,887 MPa to 13,010 MPa.
The use of mechanically graded veneers significantly influenced the longitudinal bending
strength of plywood. The density of plywood panels ranged from 723 kg/ m3 to 815 kg/ m3.
The bond strength to the shear stress reached values greater than 2.0 MPa, qualifying plywood
panels for indoor use – IR, intermediate use – IM, and external use – EX, according to the
standard project 31:000.05-001/1 (ABNT, 2004). Results also indicated that rubber wood has
great potential for industrial production of plywood for general use – GER, industrial use –
IND, and to form concrete – FOR.
