PP (Polypropylen)

Polypropylene is one of the most commonly used thermoplastics worldwide and ranks second in terms of production volume after polyethylene. It is produced by chain polymerisation of the monomer propene and has special structural properties due to the methyl group present in each repeating unit. This additional side chain provides greater rigidity and strength compared to polyethylene, as well as improved resistance to thermal and mechanical influences.

With a density of only 0.895–0.915 g/cm³, polypropylene is the lightest mass-produced plastic. Its partially crystalline structure (crystallinity approx. 50–70%) gives the material good strength properties while maintaining a low density. By specifically varying the polymerisation process, different modifications can be produced, e.g. isotactic, syndiotactic or atactic PP, of which isotactic PP is primarily used for technical applications.

Important properties of polypropylene:
High rigidity and hardness combined with low density.
Very good chemical resistance to many acids, alkalis, solvents and alcohols.
High heat resistance (up to approx. 100 °C continuously, up to 140 °C for short periods).
Good fatigue resistance, e.g. in hinge joints (classic example: ‘living hinges’ in packaging).
Low impact strength at low temperatures (brittle below 0 °C), which can be improved by copolymers (PP block copolymer, PP random copolymer).
Very good electrical insulation properties, therefore widely used in the electrical sector.
Good recyclability through thermoplastic recycling.

Typical applications:
Polypropylene is found in almost all areas of daily life and industry. Examples include:
Packaging: bottles, cups, closures, films, containers.
Household goods: kitchen appliances, furniture, textile fibres (e.g. carpets, nonwovens).
Automotive engineering: bumpers, dashboard trim, interior components.
Medical technology: syringes, laboratory containers, disposable products.

Technical applications: pipes, cable insulation, hinges.

Thanks to its combination of low weight, chemical resistance and versatile processability, polypropylene is considered one of the most important all-round plastics worldwide.