New aesthetics aligned with new technical requirements in the extrusion of ceramic bodies are demanding a new approach when it comes to additives’ requirements. In the past, lubrication and proper rheology were highly appreciated, but today there are other properties that should be taken into consideration if defects such as cracks, laminations, scumming, etc. can’t appear along the process, mainly due to the higher technical requirements of the raw materials.
The pressing stage is one of the most demanding in the production of ceramic bodies. Therefore, gaining any improvements here is directly translated into savings along the production process. These improvements will help to optimize the total costs of the manufactured products by reducing losses whilst improving the quality of the shaped materials.
One of the main challenges of the Ceramic Industry is related to the lack of good quality plastic clays. Though there are many reliable sources, its cost is banning industrial usages, especially in a moment when tiles are becoming larger and larger. Furthermore, if we consider how market is moving towards higher performance requirements, this situation is not showing any ways of changing
Plasticity is the characteristic behaviour of a ceramic material to become permanently deformed after the application of an external force. This property is the most characteristic one in clays, and there are some factors that influence the plasticity and they should be considered in plasticity measurements:
- Water physical characteristics like, viscosity, surface tension…
- Particle size distribution of the solid sample and its specific surface
- Chemical and mineralogical composition of samples
- Effect of the additives added to the clay/water system
- Sample temperature
- The way to prepare the sample, particularly the energy used to mix and to process clay, water & additives
Plasticity is defined as the capacity to be deformed without being broken. Many methods available to measure it, and they are classified into two groups: direct and indirect methods.
Table1. Direct and indirect plasticity methods.
The clay does not last forever and, with limited deposits and high market demands, the best clay is very expensive. Add to that the conflict in Crimea, where the Russian occupation has choked the supply of cheap Ukrainian high-quality clay, and you face a situation where lack of supply has caused the raw material prices to increase five times since the manufacturers started using it. This is, of course, critical for the industry, but the forward leaning manufacturers go looking for alternative sources.