Polypropylene (PP) filament guide
Polypropylene is the plastic behind flip top bottle caps, food containers and car battery cases. As a filament it offers things few others can: living hinges that flex thousands of times, excellent chemical resistance and very light parts. The catch is printing it. PP barely sticks to anything, including most build plates, so it needs a specific setup.
What PP is good at
PP's standout property is fatigue resistance. A thin printed section can bend back and forth a great many times without cracking, which makes it the go to filament for living hinges, snap fits and clips. It also resists a wide range of chemicals, including many acids, bases, oils and solvents that attack other filaments, and it absorbs very little moisture.
Plain PP is one of the lightest filaments, with a density around 0.9 g/cm³ for most grades, noticeably less than PLA or PETG, so the same part weighs less. It is also semi flexible and tough rather than stiff, and that softness shows up under heat too: filament data sheets put its softening point under load at roughly 50 to 65°C, lower than PETG.
Why it is hard to print
The one thing not to get wrong
PP does not stick to glass, PEI or most standard build surfaces. The usual fix is packing tape or a sheet made of polypropylene, or a build plate sold specifically for PP. Without that, prints come loose on the first layers.
PP also shrinks and warps as it cools, so large flat parts curl at the corners. Brims, slower first layers, keeping part cooling low and a draft free space all help. Typical settings are a nozzle around 220 to 250°C and a bed around 60 to 100°C depending on the surface; follow the range on your spool, since PP formulas vary.
Filled grades such as PP-CF and PP-GF warp less and are easier to print, at the cost of the flexibility that makes plain PP useful for hinges. They also need a hardened nozzle.
When to choose PP
Choose PP for living hinges, snap fit lids, clips, chemical resistant containers and light parts that flex. Skip it for anything that needs to be stiff, for fine cosmetic detail, or when you do not want to set up a special bed surface. For tough flexible parts that are easier to print, TPU is often simpler, and for general durable parts PETG is far less hassle.
See the TPU filament guide for flexible parts and the PETG filament guide for easier durable parts.
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