Polypropylene: Characteristics
Why the lightest plastic gives more parts per kilo
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.PP is sold by melt flow rate, polymer type (homopolymer, random, impact copolymer) and additive package. Isotacticity sets stiffness; ethylene content sets impact and clarity. Converters choose grades by process: raffia tape lines, BOPP lines, injection moulding or spunbond.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Density | about 0.90-0.91 g/cm3 | Lowest of the commodity plastics, so more parts per kilogram. | standard polymer data |
| Melt flow rate (230°C, 2.16 kg) | raffia about 2-4 g/10 min; BOPP about 2-4; injection 10-50; fibre 25-40 (indicative) | Matches resin to conversion process. | industry standard (indicative) |
| Melting point | about 160-165°C (homopolymer) | Allows hot filling, sterilisation and microwave use. | standard polymer data |
| Isotacticity | typically above 95% (indicative) | Higher isotacticity gives stiffness and heat resistance. | industry standard (indicative) |
| Carbon content | about 86% by mass | About 3.1 t CO2 per t if incinerated. | stoichiometric |
Commercial grades
- Homopolymer raffia (woven sacks, FIBC)
- Homopolymer BOPP film
- Homopolymer injection (caps, housewares)
- Random copolymer (clear containers, PP-R pipe)
- Impact or block copolymer (automotive, crates, buckets)
- Fibre and spunbond/meltblown nonwoven
- Talc- and glass-filled compounds
- Recycled PP (mostly non-food)