# Determination of Carbon Black Content & Ash Content - Rubber Accessories

## Pyrolysis Method

### APPARATUS AND GLASSWARES

• Electrical combustion furnace – maintained at 1000°± 25°C.
• Muffle furnace – 550°± 25°C, 1000 ± 25°C
• Silica or porcelain crucible
• Combustion tube.
• Porcelain  boat (combustion type)
• Nitrogen gas cylinder.
• Weighing balance.
• Desiccator

### PROCEDURE

• Determination of fillers, in test specimen
• Heat the furnace with the combustion boat to temperature 1000± 25°C.
• Place the boat in furnace maintained at temperature 1000°C for 15 minutes.
• Cool in Desiccator and weigh accurately to 0.001 g as M1.
• In the boat, weigh about 1 g of homogenized sample and take the mass of sample with boat as M2.
• Draw out the combustion tube a little bit from the hot zone and pass nitrogen for 1 minute to drive the air.
• Put the boat with sample into the combustion tube slightly away from hot zone.
• Connect the nitrogen gas flow and push the tube such that boat is in the hot zone of furnace.
• At first dense, black-brown smoke will come out of combustion tube and finally turns into white smoke.
• When white smoke becomes thinner, draw out the combustion tube from the furnace.
• Continue the nitrogen flow for 2-3 minutes more.
• Cut off the nitrogen supply into the tube.
• Take out the boat carefully avoiding spilling and keep it in a Desiccator till it is cooled.
• Weigh the boat with the ignited sample as M3.

### Calculate total fillers, percent by mass accordingly as follows

Total fillers, percent by mass = M3 – M1 x 100 / M2 – M1

Where

• M3= mass in g of the boat with the sample after ignition,
• Ml = mass in g of empty boat, and
• M2 = mass in g of the boat with sample.

### Procedure:-

• Heat the crucible at 550°± 25°C in muffle furnace for half an hour.
• Remove the crucible and cool in Desiccator.
• Weigh quickly and note the dry weight of crucible as B.
• Weigh 1.0 g of test specimen into this weighed crucible. Note mass of sample as C.
• Place the crucible with sample in the furnace and close the door completely.
• After 1 hour, open the furnace door 3 to 5 cm and continue heating for 30 minutes.
• As soon as all carbonaceous materials are burned off, remove the crucible from the furnace.
• Cool in a Desiccator and weigh the mass of ash and crucible as A.

### Calculate ash, percent by mass as follows:-

Ash, percent by mass = A - B   x 100 / C

Where

A = mass in gram of ash and crucible.

B = mass in gram of crucible.

C = mass in gram of test specimen

### CALCULATION:-

Calculate the carbon black content as follows:

Carbon black, percent by mass = Total fillers – Total ash.

REFERANCE: - IS 3400 (part 22):1984 Methods of test for vulcanized rubber – chemical analysis.