Bentonite has been used in ceramics for many years due to the way it performs in terms of plasticity and workability. Nonetheless, there are some alternative approaches that may ease its replacement, as they show some undesirable side effects when introduced into formulations.
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.
Clay body formulation has been in a continuous evolution since the modern-day tile industry trended towards large and more aesthetic in appearance. This evolution is calling for adjustments to achieve required performances whilst optimizing production costs.
The video underneath shows an Indonesian factory producing large porcelain tiles. These white body tiles measure 120cmx60cm and, as you can see, due to its large size and thinness, they break easily during the production process, especially in those plants where layout imposes direction and/or level changes. Breakages and cracks are usual and happen for several reasons. The good news is that there are also various ways to deal with them. In the video, adding additives was the most effective way to mitigate this breakage rate.
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.
Having a less fragile clay body after the tile is pressed is not only down to buying expensive high plasticity clay. There are workarounds to increase the Ceramic Green Strength without emptying your pockets. Read on to find a solution that fits your production.
Market trends are not easy to predict, but sometimes they are even difficult to evaluate in hindsight. The popularity of large ceramic tiles was initially a result of creative Italian producers experimenting with their product. Why they became so popular is still subject to discussions, but their impact on the market means that manufacturers need to adjust their business models to be competitive.
Hard trends in tile production clash with geopolitical issues when we try to explain the reasons why producers look for alternatives to Ukrainian clay these days.