Material guide
PP, polypropylene
PP, polypropylene, is the chemically resistant workhorse in the tank and in the chemical environment. Light, cheap and almost indestructible against acids and bases, easy to weld into complete structures. Where something has to handle aggressive liquids without rusting, PP is often where you land.
What it is
PP, polypropylene, is one of the most used plastics in industry and in everyday life. It is closely related to polyethylene but slightly stiffer and more heat resistant, and it stands out above all for its chemical resistance: PP does not care about most acids, bases and salts, not even at high concentrations. It is light, takes on practically no moisture and welds excellently, which makes it the base material for tanks, tubes and vats in chemical and process engineering. Add a low price and you can see why PP is a first choice when a chemical environment meets volume. The group has several grades, among them the flame retardant PPs, explained further down.
Properties
Handles most acids and bases even at high concentration
Lighter than most engineering plastics
Takes on practically no moisture, the dimensions are not affected by a wet environment
Easy to weld into tight, complete structures such as tanks and vats
Slightly stiffer and more heat resistant than polyethylene
Food approved in suitable grades
Common applications
PP sits where chemicals and liquid have to be handled: tanks, vats, containers, tubes and tube fittings in process and environmental engineering, plus guards, covers and interior fittings in wet environments. The welded structure is one of the strengths of PP, so the material is common in fabricated tank builds and ventilation parts for aggressive media. PP is also a standard choice for cutting boards and parts in food environments in suitable grades.
Limitations
PP is not a high temperature material and gets more brittle in the cold than polyethylene, so for impact loaded parts at low temperatures there are better choices. It is not especially stiff or dimensionally stable under load either, so POM or PET suits precision parts with tight tolerances better. The raw material is sensitive to UV over time unless it is stabilized, so for outdoor use in the sun you want a UV grade. Bonding is awkward; welding or mechanical fastening works better.
Our PP qualities handle 100 °C in continuous use. In the cold the material gets more brittle, and how early that happens depends on the grade, so raise the operating environment with us if the part is going to sit cold.
Grades and variants
The PP group differs in additives and properties. The grades share the same chemical resistance but are adapted for fire requirements, stiffness and recycling.
Base grades
- PP, the most common grade. Chemically resistant and weldable, for tanks, tubes and parts in chemical environments.
- PPs, flame retardant polypropylene. The same chemical resistance as ordinary PP but with flame retardant properties, for environments with fire requirements. Look at the lowercase s. PPs is polypropylene, while PPS with a capital S is polyphenylene sulfide, a completely different and considerably more expensive material. Write it correctly when you order and we both avoid an expensive surprise.
Additives and reinforcements
- GF, glass fiber reinforced for higher stiffness and heat resistance.
- Reg, recycled material where it suits.
Not all grades are available in all formats, and PP is typically supplied in natural unless stated otherwise.
Machining
PP is sawn, milled, drilled and welded. Bonding works poorly, the surface is too slippery, so welding or mechanical fastening is the way. The material is soft and tends to smear at too high a speed, so keep the spindle speed down and let the chips clear.
Formats we can supply
PP comes in a wide span: sheets, round rods, tubes and hollow bars, plus film, roll, welding rod, Multiwall and Twin-Wall for welded and lightweight structures. You can see formats and dimensions in the range. Want a piece cut to size? Enter the measurements in VisualCutter and you see the price straight away.