IS: 9316 (Part 3)-1987
DETERMINATION OF COAGULAM CONTENT
(SIEVE RESIDUE)
1. SCOPE
1.1 This standard (part 3) prescribes a method for the determination of the coagulum content (sieve
residue) of natural rubber latex concentrate containing preservative agents and also for the
determination of the coagulum content (sieve residue) of synthetic rubber lattices.
residue) of natural rubber latex concentrate containing preservative agents and also for the
determination of the coagulum content (sieve residue) of synthetic rubber lattices.
2. TERMINOLOGY
2.0 For the purpose of this standard, the following definition shall apply.
2.1 Coagulum; Sieve Residue- The material, comprising pieces of coagulated rubber, latex skin and
coarse foreign matter, retained under the conditions of the test on a stainless steel wire cloth with
an average aperture width of 180± 10 μm.
2.1 Coagulum; Sieve Residue- The material, comprising pieces of coagulated rubber, latex skin and
coarse foreign matter, retained under the conditions of the test on a stainless steel wire cloth with
an average aperture width of 180± 10 μm.
3. APPARATUS
3.1 Test Filter- consisting of a disc of stainless steel wire cloth with an average aperture width of
180±10μm (180 micron IS Sieve)
(See IS: 460(part 1)-1978*)
3.2 Two Stainless Steel Rings- of equal internal diameter between 25 and 50 mm.
3.3 Oven- capable of being controlled at 105±2°c
3.4 Desiccators
3.5 Beaker- of capacity 600-ml which has a lip.
180±10μm (180 micron IS Sieve)
(See IS: 460(part 1)-1978*)
3.2 Two Stainless Steel Rings- of equal internal diameter between 25 and 50 mm.
3.3 Oven- capable of being controlled at 105±2°c
3.4 Desiccators
3.5 Beaker- of capacity 600-ml which has a lip.
4. REAGENTS
4.1 Potassium Oleate or Ammonium Laurate- surfactant solution 5 percent (m / m), of pH 10 (for
use with natural rubber lattices).
4.2 Water Soluble Ethoxylated Alkyl Phenol- surfactant solution 5 percent (m/ m) (for use with
synthetic rubber lattices).
4.3 Litmus paper
use with natural rubber lattices).
4.2 Water Soluble Ethoxylated Alkyl Phenol- surfactant solution 5 percent (m/ m) (for use with
synthetic rubber lattices).
4.3 Litmus paper
5. PROCEDURE
5.1 Weigh 200 1g of the laboratory sample into the beaker. Add 200ml of the appropriate surfactant
solution and mix thoroughly. Dry the test filter to constant mass in the oven, controlled at 105 ±2 °c
and weigh to the nearest milligram. Record the mass (m1). Firmly clamp the test filter between the
stainless steel rings.
Note – if the wire cloth is not clean, immerse it for 2 min in boiling nitric acid (density 1.42 g/ml) and wash it with water
before drying it to constant mass and weighing
5.2 Wet the test filter with the same surfactant solution and pour the latex-surfactant mixture into
the test filter. Wash the residue on the wire cloth with the same surfactant solution until it is free
from latex. With natural rubber latex concentrate, wash with water until the washings are neutral to
litmus. With synthetic rubber latex, wash with 200ml of water. Carefully remove the wire cloth
containing the wet coagulum from the clamp and swab the underside with filter paper.
5.3 Heat the wire cloth and coagulum for 30 min in the oven, controlled at 105± 2 °c allow cooling in
the desiccator and weighing. Return to the oven at 105± 2 °c for a further period of 15 min, allow to
cool and re-weigh. Repeat the drying for 15 min periods until the loss in mass between successive
weightings is less than 1 mg.
solution and mix thoroughly. Dry the test filter to constant mass in the oven, controlled at 105 ±2 °c
and weigh to the nearest milligram. Record the mass (m1). Firmly clamp the test filter between the
stainless steel rings.
Note – if the wire cloth is not clean, immerse it for 2 min in boiling nitric acid (density 1.42 g/ml) and wash it with water
before drying it to constant mass and weighing
5.2 Wet the test filter with the same surfactant solution and pour the latex-surfactant mixture into
the test filter. Wash the residue on the wire cloth with the same surfactant solution until it is free
from latex. With natural rubber latex concentrate, wash with water until the washings are neutral to
litmus. With synthetic rubber latex, wash with 200ml of water. Carefully remove the wire cloth
containing the wet coagulum from the clamp and swab the underside with filter paper.
5.3 Heat the wire cloth and coagulum for 30 min in the oven, controlled at 105± 2 °c allow cooling in
the desiccator and weighing. Return to the oven at 105± 2 °c for a further period of 15 min, allow to
cool and re-weigh. Repeat the drying for 15 min periods until the loss in mass between successive
weightings is less than 1 mg.
6. CALCULATION
6.1 The coagulum content, expressed as a percentage by mass of the latex, is given in the following
formula:
M2― M1 × 100
M0
Where,
M0 = Mass, in grams, of the test portion;
M1 = Mass, in grams, of the wire cloth; and
M2 = Mass, in grams, of the wire cloth plus the dried coagulum.
6.2 If the results of duplicate determination do not agree to within 0.01 percent (m/m), carry out
two further determinations.
formula:
M2― M1 × 100
M0
Where,
M0 = Mass, in grams, of the test portion;
M1 = Mass, in grams, of the wire cloth; and
M2 = Mass, in grams, of the wire cloth plus the dried coagulum.
6.2 If the results of duplicate determination do not agree to within 0.01 percent (m/m), carry out
two further determinations.
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