The processing characteristics of nitrile rubber depend to a large extent on the content of ACN, the cyano group strengthens the intermolecular force, the molecular chain compliance decreases, and macromolecules are prone to network structure or branched chain, and these structural properties affect mixing. Nitrile rubber mixing has high energy consumption, and the compounding agent is difficult to disperse in the rubber material, which may be related to the large intermolecular force.
Nitrile rubber has a higher viscosity than general rubber, and Mooney compound with 26-40% acrylonitrile content has a viscosity of 90-120. The energy consumption of rubber processing is directly proportional to the viscosity of raw rubber. Nitrile rubber mixing heat, which is different from isoprene rubber and styrene-butadiene rubber, this kind of rubber in high temperature and high mechanical stress mixing, often produce a structural effect, so under the condition of heating and extending the mixing time, it will lead to increased viscosity, increased rubber viscosity, and the formation of gel, processing is difficult.
Low-speed mixing, rubber material heating is low, so it is advisable to use a mixer with a speed of 10-20r/min for mixing, and it is appropriate to use small auxiliary distance, low speed ratio and batch feeding and other process conditions and operation methods. Nitrile rubber often adopts a unique process measure to reduce the temperature of the rubber material: carbon black and softener are added to the mixer at the same time, which can slow down the structure and prolong the scorch time, but the dispersion of the compound is slightly reduced, when the amount of carbon black is higher than 80 parts, it should be added in three parts, which can reduce the degree of structuring and improve the performance of the rubber material. It is difficult to disperse sulfur in nitrile rubber, it is best to add it in the mixer initially, so that the dispersion can be increased by 10%, and the accelerator is finally added in the opening machine.
