Polystyrene is a thermoplastic polymer. It is a large molecule made of many repeating monomers (small units) and has the ability to mold above certain temperatures. It softens when it's heated which allows us to use it making a variety of products (PlasticsEurope, n.d.). 

 

   Polystyrene is made of monomers called styrene. Styrene undergoes polymerization, which is simply stringing together or bonding several monomers (ChemicalSafetyFacts, 2016). After that, it is in the form of pellets. In order to get the desired shape to construct a particular product, it may be extruded (melted and put through a die), thermoformed (exposed to high temperatures and moulded) or injection moulded (melted and placed in a mould cavity in which it solidifies). These three methods allow the plastic to form into different shapes (PlasticsEurope, n.d.).