Views: 0 Author: Site Editor Publish Time: 2025-01-16 Origin: Site
Process parameters affecting internal mixer mixing
1. Mixing procedure and order of adding materials
Generally, the activator should be added after the addition of EPDM rubber and before the addition of carbon black; or added at the same time as carbon black;
Operating oil should be added immediately after the addition of carbon black and other fillers. Adding it too late may cause the rubber surface to slip and be difficult to disperse, thereby prolonging the mixing time;
Vulcanizer and accelerator should be added after the other compounding agents are dispersed, but the temperature should be controlled below 100 degrees to avoid scorching during mixing.
2. Mixing temperature
When the material is mixed in the internal mixer, a lot of heat will be generated due to friction and shearing.
When the rotor speed is increased and the pressure of the top bolt on the internal mixer is increased, the temperature will rise due to the increase in the shear force and friction of the rubber.
During the mixing process of the internal mixer, the rubber temperature continues to rise, and the mixing is generally completed when the specified upper limit temperature is reached. When the mixing temperature is low, the viscosity of the rubber is large, the wettability and dispersibility of the compounding agent are poor, the equipment load is large, but the shear force is also large, which is beneficial for the mixing of low hardness rubber.
When the temperature is too high, the rubber becomes soft, which is beneficial to the mixing of powder and raw rubber, but the reduced shearing effect will be unfavorable for the dispersion of powder groups, and it will bring difficulties to the unloading operation after discharging.
The setting of the mixing temperature for rubbers of different formulas usually depends on the characteristics of the raw rubber or rubber (such as Mooney viscosity and hardness, etc.), as well as the characteristics of the formula (such as filler particle size, vulcanization system, etc.).
Like the discharge temperature, the starting temperature of EPDM in the internal mixer is also important for accelerating the start and mixing dispersion. The dispersion effect of starting mixing at 70 degrees is better than that at 50 degrees. High filling mixing requires higher mixing temperature, especially in large internal mixers. Preheating the oil before adding it is also conducive to diffusion and dispersion.
3. Mixing time
Although extending the mixing time during operation can improve the dispersion of the compounding agents, it is also easy to cause the rubber compound to be over-mixed or the temperature to be too high and burn.
4. Rotor speed
A lower rotor speed is suitable for mixing heat-sensitive rubbers or when serious problems occur during mixing and dispersion and the mixing time is prolonged.
NANJING HAISI is professional manufacturer of internal mixer, we supply Twin Screw Extruder, Single Screw Extruder, Plastic Recycling Extruder, Two Stage Extruder, Lab Scale Extruder, Mixing and Feeding Machine, Cooling and Pelletizing Machine, Crushing Machine and so on.
