Dump Temperature in Rubber Production

I have a bunch of doubts, it will be helpful if anyone can help me with this.

  1. On which basis we are fixing the kneader’s dump temperature for various rubbers in kneader mixing?
  2. What are all the important parameters in setting the dump temperature?
  3. Are there any different rheo attributes for kneader mixing and open mixing?
  4. Will TS2 and TC90 be affected when the ML value of the compound changes?

For instance, when I mix NR compound of 80 hardness in the open mill , the resulting ML is 13 to 15. But when I tried mixing in kneader , the resulting ML is 20 to 22. I have tried various mastication time in kneader (about 3 to 12 mins). And my tried various dump temperature 105°C to 130°C . When I mix in kneader ,the ML is high and TS2 ,TC90,hardness is low. I don’t know how to decrease the ML in kneader mixing.



  1. A higher temperature will melt more ingredients, making the dispersion much easier. Too high temperatures will break down your elastomers or cause side reactions.
    The type of rubber (and formulation) will determine your dump temperatures. CR rubbers have low dump temperatures, very soft EPDM just don’t cause enough friction to go high.
  2. I assume you should mix as economically as possible. Shortest time, high energy input to have a good dispersion.
    If your dispersion is not good enough, you need to change your mixing procedure.
  3. viscosity might differ a bit, open mixing takes far longer.
  4. yes, but the question too vague or broad to give a usefull answer.

Have you tried two stage mixing? First stage up to 150°C fe and second stage with accelerators up to 100°C one day later?

Above is a snippet.