ZONE – I
Loading + wetting stage – Formation of a Single Mass of filler and rubber – penetration of Polymer in to filler voids – As the C-black is slowly absorbed into the rubber the torque increases. When the volume of rubber + C-black becomes equal to the chamber Vol., the raw comes to the lowest position, the raw hydraulic pressure on the stock disappears. The power shows first peak. More and more C-black gets absorbed, Stock volume becomes lower & the power curve comes down.
ZONE – II
Most of the real dispersion work takes place. The filler agglomerates are gradually distributed through the polymer and then broken down tto their ultimate size. The power curve also starts rising till the whole stock with oil & C-black has consolidated. At this juncture the second power peak occur .
ZONE – III
Plasticization takes place.
The power curve decrease beyond the second power peak has been found to obey first-order kinetic law,
Log [(Po – Pt)/(Pt – Px)] = Kt
The mixing should continue till dispersion half time. (i.e. (Po-Pt)/(Pt-Px) = 0.5) after 2nd power Peak.
TOTAL MIXING TIME = Black incorporation time + Dispersion half-time.
To handle variety of rubber compounds on the same mill required that mill to have.
Independent speed control on both rolls
Widely variable speed on both rolls
Independent temperature control on speed, friction ratio and temp. to be adapted to each individual .
Hydraulically operated nip adjustment