Kaolin is one of a large number of minerals used in plastics industry as a filler and extender.  The initial use for kaolin in the industry was as a cheap filler and extender in polyvinyl chloride (PVC) and as a processing aid in polyesters.  The main polymers in which kaolin is now used are in nylon, PVC and thermoplastic resins with polyolefin polymers such as polyethylene of lesser importance.

Polymers are long chains of monomers, generally organic but some inorganic systems do exist.  Polymers can be made from one monomer (homopolymer) or more than one.  Fore example, polyethylene is made from a single monomer (ethylene) and ABS from three (acrylonitrile, butadiene and styrene).  

In many cases the polymer cannot be used in a virgin state but must be mixed with other ingredients to produce an end product that will have the desired performance characteristics.  This mixing process is known as formulating or more commonly compounding.  This process may modify the polymer in the sense that a chemical reaction occurs, but this is not always the case.  The purpose of compounding is to produce a product with the required performance characteristics desired by the customer at an acceptable cost.