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In the production of carbon materials, the materials prepared according to the formula are dispersed systems, which are neither uniform nor able to form a whole with a certain strength. In order to make the material structure have good uniformity and retain plasticity so that it can be formed, it is required to mix the various materials in certain equipment to achieve uniformity. This makes the various types of aggregates The process of uniformly mixing the components, various particle sizes and binders to obtain a plastic paste is called kneading – the so-called mixing means to use a certain method (such as Mechanical stirring), the process operation that makes the materials evenly distributed is called mixing. A liquid binder is added during mixing, so it is also called dry mixing.
The so-called kneading is to add liquid binder to dry materials of different types and particle sizes, and use mechanical stirring method to distribute the materials evenly, and make the binder thinly and evenly wrap around the surface of the powder particles, and penetrate into the powder. The process of making the material have a certain plasticity and density in the micropores on the surface of the particles is called kneading. In the actual production of carbon materials, the dry materials are generally mixed first, and then the binder is added for kneading, so the complete process should be called mixing and kneading. However, in the process, it is customary to call it kneading (which includes mixing), but it is inappropriate to still call the operation after adding the binder as mixing.
The purpose of mixing in the production of carbon materials:
① Make various materials evenly distributed (normal distribution).
② Make aggregates of different particle sizes evenly distributed and fill the gaps between large particles with smaller particles to improve the density of the material.
③ Make the dry material and binder evenly distributed, and the binder evenly covers the surface of the dry material particles and partially penetrates into the pores of the particles. The adhesive force of the binder combines all the particles with each other and gives the paste plasticity, which is convenient for forming.
④Make the dry material and adhesive have a uniform structure, a suitable temperature, and become a paste with good plasticity, making it easy to press.
According to the different types of materials to be mixed, mixing methods are divided into two categories:
①Cold mix and knead. No asphalt binder is added during kneading, or the asphalt binder is added in solid powder form. Put the materials into the container, and use the rolling of the container and the weight of the materials themselves to blend the materials. This process is mainly used for molded products. This method is commonly used for batching two materials with different densities, such as graphite/metal materials.
②Hot kneading. Since asphalt is solid at room temperature, in order to mix the asphalt with the aggregate in a liquid state and infiltrate the aggregate surface, it is usually mixed under heating. This process is mainly used for ingredients that use asphalt or resin as a binder, or for kneading materials with similar density.
