China Clay or Kaolin

Abstract

Clays of various sorts are widely available throughout the world and have been used in polymer composites, especially those based on elastomers, since the early days of their industrial application. While there are a large number of clay materials, the main ones used in polymers are based on the mineral kaolinite and are often referred to as kaolin or china clay.

The china clays themselves have limited application in thermoplastic and thermoset applications. This is due to a number of factors, such as poor color and heat aging, especially in polypropylene. The water of crystallization is also an issue for water-sensitive polymers such as nylon and thermoplastic polyesters, as it can be released during processing. Many of the problems are overcome by calcination, and calcined forms are more widely used for these polymers.

On the other hand, china clay is a widely used white filler in the rubber industry. Depending on particle size, it can be used as a semi-reinforcing filler (hard clay) or a non-reinforcing filler (soft clay). Common elastomer applications include chemical liners, bicycle tires, conveyor belts, shoe soles, gaskets, and flooring.