Tapping
The
latex is extracting from rubber tree ( Hevea brasiliensis )
by skillfully slicing a groove into the bark of the tree with a specialty
knife. The trees must be approximately 6
years old and 150mm in diameter in order to be tapped.
The
tapping work is done at night or in the early morning when the temperature is
lower, so that the latex will drip longer before coagulating.
Ammonia solution are sometimes added to the collection
cup to prevent natural coagulation and allow the latex to remain in liquid
state. Liquid latex is used to produce
latex concentrate for manufacture of dipped goods or coagulated under clean and
controlled conditions. Natural rubber
latex concentrate, is preserved with ammonia solution, contains 60% Dry Rubber
Content ( DRC ).
Coagulating & Milling
Latex
is a suspension of isoprene, microscopic natural
rubber particles in an aqueous medium. These
particles scatter light, making the latex solution appear white and homogeneous
like milk. The surfaces of the latex
particles are charged, which creates forces of repulsion between them that keep
them from coagulating. In the coagulation process formic
acid neutralizes these charges, thereby eliminating the forces of
repulsion between the particles.
The
coagulated latex block are then pressed to remove water by passage through
rollers. The last pairs of rollers are grooved
and thus produce ribbed sheets. The ribs
increase the surface area and facilitates drying.
The
serum left after latex coagulation is rich in quebrachitol
(QCT), and various water-soluble materials such as sugars, lipids,
proteins and minerals, which can cause water pollution if the serum is directly
discharged into the environment.
Washing & Drying
The
freshly sheeted rubber are then soaked in running water for a short time after
milling to wash off the residual non-rubbers and, to prevent discoloration and
mold growth.
Sheets
were hung up to drip off the remaining water for 4 to 6 hours preferably in the
shade to drain off the surface moisture and thereby reduce the smoking period.
Smoking
Dripped sheets which contain about 20% moisture
are dried in a smoke house. Smoking
enables the sheets to absorb creosotic and other antiseptic substances which
provide a preservative effect and anti-oxidant effect on to the rubber. Temperature of the smoke house maintained at range
between 48-54 °C.
Generally,
smoking could be completed within 4-5 days.