Polypropylene
Polypropylene – is a polymer from the group called polyolefins, built from monomer units with the following formula: –[CH2CH(CH3)]. It is obtained by low-pressure polymerization of propylene. With polyethylene, polypropylene belongs to the most widely used plastics. Items manufactured from this material are usually marked with the symbol PP.
Polypropylene is a thermoplastic hydrocarbon polymer, which means that it can be easily brought to the liquid state when heated and then solidifies back when temperature drops, without any change to its chemical properties.
Processing
Manufacture of finished products from pellets is carried out by two processes: injection and extrusion.
By injection you can obtain from PP thin items with fine detail and high surface area. Many household appliances are made using this method, such as transportation boxes, containers, various packages, etc. Injected items are characterized by high rigidity and gloss.
Items manufactured by extrusion include: pipes, insulation of steel pipes, insulation of electric wires, plates, various shapes, films, fibres. Films are manufactured primarily by extrusion through crevice nozzle and stretching, as well as by extrusion with free blowing. Films are widely used as packaging material , including for food products.