Reverse mixing method of rubber
Reverse mixing method, also known as reverse or reverse mixing method, refers to the method of first adding other additives except vulcanizing agents and accelerators to the mixer, and then adding raw rubber for mixing. Commonly used for polymers with limited self-adhesiveness, such as EPDM. This process is often used when the polymer content is low (15% -25%). The main advantage of the reverse mixing method is to improve dispersion, shorten mixing time, and is suitable for mixing raw rubber with poor viscosity and high filling ratio. The disadvantage is that the required power is high in the early stage of mixing, which sometimes leads to the shutdown of the mixer, followed by poor dispersion. It is worth noting that this reverse mixing method cannot effectively disperse the reinforcing filler. If fine carbon black particles are used, the rubber material can be mixed using traditional mixing methods or later refueling processes.
When EPDM is mixed in reverse order, after adding fillers, operating oil, and small materials, it is allowed to mix briefly before adding polymers and dropping the top bolt. Sulfurizing agents can be added together with small materials such as zinc oxide and stearic acid, and if they have strong activity, they can also be added in the later stage of the mixing cycle. Difficult to mix vulcanizing agents can also be added together with small materials, and the remaining part can be added in the later stage of mixing. But the temperature of the adhesive should be strictly controlled.
For most ethylene propylene rubber materials without special dispersion requirements, the reverse mixing method can be used.