Principle
The principle consists in measuring
the resistance which the carbon
black puts up against the rotating
blades during oil addition and in
determining the carbon black absorption.
The high-precision burette
adds liquid as a titrant to the powder
sample in the mixing chamber.
As the liquid wets the sample, three
distinct phases can be observed in
the torque curve:
• Free flowing phase
• Agglomeration phase
• End phase
During the free flowing phase,
liquid is absorbed into the structure
of the carbon black. Upon absorption
of sufficient liquid, the particles
begin to adhere to each other and
form agglomerates. Resistance to
mixing rises, indicated by a sharp
increase in torque.
The oil absorption number of
carbon black is directly related to
the processing and vulcanization
properties of the rubber compounds
prepared with these carbon blacks.
A maximum torque (saturation) is
reached, followed by a state
change from liquid into solid to
solid into liquid.