The binder function has two aspects:
1. When it is in liquid state, the carbonaceous aggregate and powder are wetted, bonded and kneaded into a plastic paste. After the paste is formed under pressure and cooled, the binder is hardened and the aggregate and powder are consolidated into a green .
2. The green body is fired at a high temperature, at this time the binder participates in the carbonization reaction and forms a good solid state combination, so that the product obtains a fixed geometry. The binder is within the appropriate temperature range
It is a flowable liquid that can be absorbed by carbonaceous aggregates and powders and can penetrate into the voids of aggregates and powders, and knead to form a plastic paste within a certain temperature range. This paste has a good Viscoelasticity and lubricity.
Viscoelasticity means that the material flows viscously under a certain temperature or under long-term load, while it has elasticity under low-temperature or short-time load. Viscoelasticity has a certain influence on the molding effect (compression effect). Lubricity refers to the
The mutual position of the aggregate particles is easy to move. After being filled with each other to form a stable arrangement, the aggregate particles can be prevented from being crushed. The paste should have good plastic deformation ability during the molding process
After cooling, the green body is in a hardened state after cooling. During this change, the green body should not have some sharp changes in its shape (such as expansion and contraction). When the green body is roasted, the binder is heated to a certain temperature and becomes liquid again.
After a long time of pyrolysis and polycondensation, it is finally carbonized into pitch coke, and at the same time, the aggregate and powder are firmly combined. The coke left in this carbonization process should be as much as possible (ie, the coking value is high). During roasting
The green body should not produce larger volumetric shrinkage expansion (excessive shrinkage expansion will cause cracking of the roasted product).
For the production of graphite electrodes, it is desirable that the coke after the carbonization of the binder is easy to graphitize, and has a linear expansion coefficient similar to that of carbonaceous aggregates at high temperatures for graphitization.
