Polypropylene is a light, low-cost plastic with excellent resistance to acids, alkalis and most solvents. It is easily injection moulded and its sheet is hot-air or extrusion welded into chemical tanks, scrubbers and ducts that can run hotter than PVC. It is used for containers, caps, living hinges, battery boxes, pipes and lab equipment.
Quick facts
- Type
- Semi-crystalline thermoplastic
- Density
- About 0.90–0.91 g/cm³ (floats on water)
- Service temperature
- Up to about 90–100 °C
- Chemical resistance
- Excellent to acids and alkalis
- Grades
- Homopolymer (stiffer), copolymer (tougher in cold)
- Joining
- Hot-air, extrusion and butt welding
PP or HDPE?
| PP | HDPE | |
|---|---|---|
| Max temperature | Higher (about 100 °C) | About 80 °C |
| Stiffness | Higher | Lower |
| Toughness in cold | Lower (homopolymer) | Better |
| Living hinges | Excellent | Poor |
Values are typical for unfilled grades. Grades from different makers differ; ask for the supplier's data sheet when it matters.
Typical uses
- Chemical and plating tanks
- Fume scrubbers and ducts
- Moulded caps, containers and hinges
- Pipes and fittings
- Battery cases
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Questions
- PP or PVC for a chemical tank?
- PP handles higher temperatures (up to about 90–100 °C); PVC is stiffer and self-extinguishing but softens around 60 °C.
- Can PP be glued?
- Hardly; it is joined by welding or fasteners.
- What is a living hinge?
- A thin moulded strip that bends thousands of times, like on bottle caps. PP is the best common plastic for it.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.