Which material is NOT a natural polymer?

Polyester is categorized as a synthetic polymer, meaning it is man-made rather than derived from natural sources. It is produced through a chemical reaction between an alcohol and a carboxylic acid, typically involving petroleum-based products. This process contrasts with natural polymers, which are formed by natural biological processes.

Natural rubber, amber, and casein, on the other hand, are all examples of natural polymers. Natural rubber is derived from the latex of rubber trees, amber is fossilized tree resin, and casein is a protein found in milk, all of which are products of natural biological systems. Understanding the distinction between synthetic and natural polymers is crucial, particularly their origins and applications in various industries.