Polypropylene (PP) is a synthetic material which is used in a similar way to nylon, but with a maximum temperature of 120°C. It is a thermoplastic polymer providing good chemical and heat resistance at a reasonable cost. Polypropylene is rugged and unusually resistant to many chemical solvents, bases and acids. PP is chemically stable- composed of hydrogen and carbon atoms. When polypropylene is incinerated only water vapour and carbon dioxide are produced. Among fossil fuel-based resins, only polypropylene can be considered sustainable. It is a semi-crystalline, white, semi-opaque commodity thermoplastic made in a very wide variety of grades and modifications. Like polyethylenes, PP has good chemical but poor UV resistance (unless stabilized or protected). Due to thermal stability issues with materials such as PP, additives such as anti-oxidants are invariably used during processing.