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Polypropylene (PP) moulding: lightweight, chemical-resistant components

We injection-mould polypropylene components to customer drawings: a light, cost-effective thermoplastic with very good resistance to chemicals and fatigue.

What is polypropylene (PP)?

Polypropylene is a polyolefin like polyethylene, but with a methyl group on every repeat unit: this makes it stiffer and able to withstand higher temperatures. With a density of about 0.9 g/cm³ it is one of the lightest plastics.

It resists fatigue: with the right wall thickness it allows living hinges that bend thousands of times without breaking. It can be talc-filled or glass-fibre reinforced for greater stiffness. At low temperatures it becomes brittle, less so in copolymer grades.

Properties of polypropylene

  • High chemical resistance
  • Good fatigue resistance
  • Low specific weight
  • Good transparency (if isotactic)

Indicative continuous service temperatures for the most common grades: the exact value depends on the grade and formulation and should be checked on the data sheet of the chosen material.

What is polypropylene (PP) used for?

  • Caps, closures and living hinges
  • Containers and trays
  • Components for household appliances
  • Parts in contact with detergents and chemicals
  • Lightweight components for furniture

How we mould polypropylene (PP)

Polypropylene needs no drying and moulds with short cycle times. Like polyethylene it has high shrinkage, which is offset in the mould design and with uniform wall thickness.

PP or another material?

The material is chosen according to the conditions of use of the component. The closest alternatives:

  • PE Polyethylene

    Compared with polyethylene it is stiffer and more heat-resistant, but less tough in the cold.

  • ABS Acrylonitrile butadiene styrene

    ABS has a glossier surface and holds tolerances better, but it is heavier and less resistant to chemicals.

  • PA 6 / PA 66 Polyamide

    For mechanical components under load, such as gears and bushings, polyamide offers more strength and less wear.

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Do you have a component to make in PP?

Send us your drawing or a sample: the contact form opens with the material already selected. If the material is still open, we will choose it together.

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