Extrusion is an effective technique to manufacture products with a uniform, even complex cross section. The basics of this technique are simple: heat the to-be-extruded material until it can deform somewhat, and force this material to flow through a mould or extrusion head with the desired cross section and shape. Extrusion of dense polymers results in dense products. However, incorporating a blowing agent in the process will add porosity to the products, leading to low-density and sometimes with excellent acoustic or thermal isolation properties.
