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Various comminution units are used in the pharmaceutical, cosmetics, food and chemical industries for the fine processing of solids in liquids. Depending on the product properties, different types of grinders with different grinding systems are used.

One of these applications is the processing of zirconium oxide for the purpose of thin-layer application (8-10 μm) as an insulating ceramic. In the regrind, no conductive particles, such as metallic abrasion of the rotor-stator system should occur. To avoid this, grinding chamber linings made of polyurethane are used.

In the specific case described, a customer contacted asma with the requirement to develop a more durable polyurethane coating. In addition to the classic signs of wear, conventional polyurethane linings repeatedly showed the fault pattern that water-filled bumps (blisters) formed between the metal body and the coating.

An analysis of the process by the application technicians at asma derived a detailed requirement profile for the polyurethane formulation. Working with an alkaline suspension (pH value 11-12) requires not only the highest abrasion resistance, temperature and chemical resistance, but above all the least water vapor diffusion to protect against osmosis. This was the main cause of blister formation and thus also the failure of the conventional polyurethane coating.

With the knowledge gained, the development department at asma set to work on a formulation that was tailored to these special requirements.

The result fulfills the expectations of the customer to this day. The asma recipe made it possible to increase the service life of the wear lining from 600 to 1200 hours.

Since then there has been no early failure and therefore no defective product batch at the customer.

Mario Weninger