Immature gamar (Ginelina arborea, Linn.) plants at about the age of 10 to
12 years become infested with loranthus, a parasitic plant, and ultimately die if a
heavy infestation occurs. Gamar of 8,12,16 and 20 years age groups, having little
timber value, have been studied for the manufacture of exterior grade hardboards.
Fibre analysis and solvent extractibility show that the wood will be suitable for
the purpose. Fibre length, flexibility coefficient, fibre diameter, relative fibre
length and other related factors arc better than those of many other tropical wood
and grass species. The presence of high percentages of waxes, fats and resins makes
the fibres naturally moisture resistant.
Additive chemicals have been used in the slurry for imparting water resistance
to the boards. Fire retardant and insect repellent chemicals have been sprayed on
the damp-dry mat or on the formed boards. Heat treatment and oil wax tempering
were followed by applying protective coating with urea-formaldehyde glue and
enamel paint.
Accelerated aging tests have been conducted according to ASTM procedures.
Board specimens have been tested for physical strength, water resistance and fire
rctardance. For charring tests, a device has been developed at the Forest Research
Institute. Modulus of rupture values, as high as 7000 psi, have been obtained.
Tempered boards absored as low as 4% by weight and 1% by volume of moisture.
Even after aging tests the boards were quite water resistant, though moderate
in strength.
Pulps have been made by Cold Soda and Steaming processes. Both soaking
and pressure impregnation methods have been tried in the Soda process. Steaming
for one hour at 140 psi steam pressure has been found to be the optimum in
the other process.