Release time:

2020-10-21

1. Rotor The type and number of rotor lobes affect mixing. More lobes result in faster shear speed, higher heat generation, shorter mixing time, and potentially compromised mixing quality. Different rotor types impact mixing. Shear-type rotors have a large and wide shear zone between the rotor lobes and the mixing chamber, resulting in high shear force, high efficiency, and good mixing quality. Intermeshing rotors have a shear zone between the two rotors, resulting in lower shear force, lower heat generation, longer mixing time, and better dispersion. 2. Upper Ram Pressure The upper ram keeps the rubber compound within the mixing chamber's working area. Insufficient pressure causes the compound to slip along the chamber walls and rotor surfaces. Appropriate pressure reduces voids in the material and increases contact force. High pressure increases the compound temperature and mixing power. Insufficient loading capacity prevents the upper ram pressure from being fully effective, resulting in uneven dispersion of the compound. 3. Temperature Each type of rubber has an optimal mixing temperature range. The type and amount of raw rubber, reinforcing agents, and softeners determine the temperature rise during mixing. At the same temperature, longer mixing times lead to better dispersion. 4. Fill Level This depends on the effective volume of the internal mixer, the type of raw rubber in the formulation, and the amount of reinforcing fillers and plasticizers. The fill level should be higher for raw rubbers with high plasticity. The filling factor (by weight) should be between 0.65 and 0.75. Insufficient fill level prevents the necessary shear force from being achieved. 5. Charging Sequence The order of adding materials affects the mixing results. In automated systems, a common sequence (using multi-stage mixing, according to material requirements) is: raw rubber - pre-mixing - addition of fillers/compounding agents - pre-mixing - addition of softeners - pre-mixing - discharge. 6. Speed Speed is directly proportional to shear rate. Higher shear rates accelerate uniform mixing. Increasing speed raises the rubber temperature, reducing viscosity and shear stress. 7. Time Mixing time is related to the fill level and the temperature rise of the formulation. The mixing temperature affects the time for various rubber compounds. The internal mixer speed and upper ram pressure also affect mixing time. Therefore, auxiliary and charging times should be minimized in the mixing process. 8. Cooling Water The cooling water temperature is typically set to 15 degrees Celsius. Low-viscosity rubber compounds are not easily cooled with hot water, as they tend to stick to the rotor. High-viscosity rubber compounds use hot water cooling. Increasing the cooling water temperature shortens mixing time, reduces energy consumption, and improves production efficiency.