Polypropylene, also known as polypropene, is a thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 used in a wide variety of applications including packaging, textile
A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...

s (e.g., rope
A rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...

s, thermal underwear and carpets), stationery
Stationery has historically meant a wide gamut of materials: paper and office supplies, writing implements, greeting cards, glue, pencil case etc.-History of stationery:...

, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknote
Polymer banknote
Polymer banknotes were developed by the Reserve Bank of Australia , Commonwealth Scientific and Industrial Research Organisation and The University of Melbourne and were first issued as currency in Australia in 1988. These banknotes are made from the polymer biaxially-oriented polypropylene ...

s. An addition polymer
Addition polymer
An addition polymer is a polymer which is formed by an addition reaction, where many monomers bond together via rearrangement of bonds without the loss of any atom or molecule...

 made from the monomer propylene
Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...

, it is rugged and unusually resistant to many chemical solvents, bases and acids.

In 2007, the global market for polypropylene had a volume of 45.1 million tons, which led to a turnover of about $65 billion (~ €47.4 billion).
Most commercial polypropylene is isotactic and has an intermediate level of crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

linity between that of low-density polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...

 (LDPE) and high-density polyethylene (HDPE).