Associativity of clay
The associativity of clay refers to the combination of clay and barren material, forming good plastic muds with a certain dry strength. Generally, the clay with strong plasticity has strong associativity.
Thixotropy of clay
Thixotropy refers to the performance of the clay mud that its viscosity will decrease and fluidity will increase when it is agitated or vibrated, and it will gradually return to its original state after standing.
In actual production, it is expected that the mud has certain thixotropy, but if the thixotropy is too strong, it will affect the flow of mud in the pipeline.
Thixotropy of clay can be expressed by consistency:
The consistency of the mud used for fine porcelain is generally between 1.8 ~ 2.2.
The consistency of refined pottery is generally between 1.6 ~ 2.6.
Drying performance of clay
The drying properties of clay include drying shrinkage, drying porosity and drying strength. After the mud is dried, the particles get close to each other and shrinkage due to the evaporation of water. After the moisture is removed, the voids between the particles are occupied by air, forming pores.
In the production of ceramics, the drying strength of clay or mud directly affects the damage rate of the green body during demoulding, transportation, glazing, trimming, gilding, setting, etc. Especially when adopting mechanization and automation forming, the dry strength of the mud is required to be higher.
Sinterability of clay
The sintering performance is mainly reflected by the firing shrinkage of the clay. During the firing process of clay, due to a series of physical and chemical changes, its length or volume shrinks, which is called firing shrinkage.
In order to facilitate production control, the sintering range of clay is expected to be as wide as possible. The sintering range of high-quality kaolin is up to 200 ℃, the impure clay is about 150 ℃ and the illite clay is only 50 ℃ ~ 80 ℃.
The refractoriness of clay refers to the ability to resist high temperature without melting. In the daily-use ceramic industry, it is an important technical index for the manufacture of refractory materials such as saggers.
The fire resistance of clay depends mainly on its chemical composition. The refractoriness of pure kaolin is 1170℃ and it decreases with the increase of impurities.