Polypropylene PP

In the polyolefin filament family, Polypropylene PP is specified, supplied as filament, broom fill and strip fill, drawn in round, triangular, cross-shaped, hollow, star-shaped and rectangular sections and set in straight rows, helical, staggered, zoned, wavy and random fill patterns.

Polypropylene PP is used in custom cleaning brushes for washdown, chemical cleaning, food-process and wet sweeping applications at moderate temperature and abrasion.

It is usually weighed against Nylon PA, PBT and PET Polyester, and the deciding difference is moisture uptake and working temperature rather than anything you can read off the name.

Compare Polypropylene PP with Nylon, PBT, PET. Change material when wet stiffness, temperature, chemical resistance, conductivity, particle shedding, or surface marking becomes the limiting factor.

Polypropylene PP is medium; Shore D about 65-75; higher wet stiffness than nylon but can take a set more easily, and Polypropylene PP changes brush stiffness through filament diameter, free trim, density, crimp, and contact. Use finer filament and longer trim for conformable contact; use coarser filament, shorter trim, or higher density for stronger displacement or cutting.

Filament-level figures for this grade and the ones it is usually compared to. A finished brush behaves differently again.

The part people get wrong: the same grade can feel soft or aggressive depending on diameter, trim and density. Specify that geometry before the material, or the sample will surprise you.

Polypropylene PP takes up ≤0.03% (24h, ISO 62/ASTM D570).

Very low water absorption and strong wet stiffness.

What this means for your application: it barely absorbs water, so dry and wet contact pressure are effectively the same and the brush behaves alike on both duties.

A practical check: soak a sample for an hour and re-measure the trim. If it has moved enough to change the contact band, the grade is wrong for the duty.

Grade-dependent. Brush-filament suppliers publish maximum continuous or working limits from about 60°C to 90°C for PP. Confirm the exact filament grade before sustained hot-water or heated service.

Design to that answer rather than to a raw-material datasheet figure: a brush rating already accounts for filament working under load rather than raw polymer sitting in an oven.

Published melting point is 160–170°C. That is a material property, not an operating ceiling, and using it to justify a hot wash is the fastest way to ruin a brush.

Where it stops working: validate with a sample if the process sits near the top of that band. If the filament takes a permanent set under load, step up to PET Polyester or PBT, which hold a higher continuous temperature.

The usable limit also moves with diameter, trim and contact pressure. A fine filament under light load tolerates more than a thick one under heavy scrubbing.

Generally strong resistance to many acids, alkalis and aqueous cleaners, but compatibility still depends on the exact chemical, concentration, temperature and exposure time; strong oxidizers and some hot solvents can be unsuitable.

The same cleaner can be harmless or destructive depending on how strong it is, how hot it runs and how long it sits. Quote the concentration and the dwell time, not just the product name.

Before you commit to a quantity: Specify the exact Polypropylene PP grade or alloy, filament or profile size, color, straight or crimped form, working temperature, wet or dry use, chemical exposure, surface finish, and any required material documentation.

About 0.08 mm. Below that the filament turns fragile and breaks under ordinary contact pressure, so 0.08–3.00 mm is the working range.

Free trim runs 5–350 mm, and the two interact: a finer filament needs a shorter trim to keep useful stiffness, while a thicker one carries a longer trim and still lands pressure on the tip.

Split the range by duty: roughly 0.08–0.81 mm for light wiping, dusting and surfaces that mark easily, and 0.81–3.00 mm where residue is packed on and point pressure matters more than surface risk.

Tip treatments available on this filament: end rounding, tapered-tip grinding, anti-static coating, antibacterial coating and corona treatment.

In practical brush terms: reaching deep into a bore or crevice is a diameter problem before it is a length problem. A thicker filament on a moderate trim pushes further in before the tips fold over.

Washdown, chemical cleaning, food-process and wet sweeping applications at moderate temperature and abrasion.

Where it turns up in practice:

• Laboratory Tube Cleaning
• Household Dish, Teapot & Kitchen Detail Cleaning
• Carpet Machine Cleaning
• Beverage Equipment Cleaning
• Industrial Machine Cleaning
• Bakery Tray Cleaning

It is normally set into these constructions:

• Custom Handheld Detail Brushes
• Custom Tube & Pipe Bore Brushes
• Custom Roller and Conveyor Brushes
• Custom Floor Scrubber Sweeper Brushes
• Custom Strip Seal Brushes

The trade-off: Avoid high-temperature brushing or heavy abrasion where nylon/abrasive nylon is needed.

A usable specification carries the construction, the filament diameter and free trim, the density and contact setting, and the service conditions: wet or dry, temperature, and what the cleaner actually is.

The mistakes that most often send a sample back:

• Selecting Polypropylene PP from the material name alone without setting filament diameter, trim length, and density
• Using dry stiffness to predict wet behavior without checking moisture absorption or liquid exposure
• Ignoring trapped abrasive particles, chemical concentration, temperature, or contact motion when assessing surface risk

Reference standards behind the figures on this page: ISO 527-1:2019; ASTM D638; ISO 62:2008; ASTM D570-22; ISO 868:2003; ASTM D2240-15(2021); ISO 4892-3:2024; ASTM G154-23; UL 94; ISO 13061-1; ASTM D143.

Source: Perlon — Technical brush filaments — polyolefin grades. Polypropylene filament limits move with the grade and the draw, and the spread between published figures is wide enough that the earlier single 79°C / 107°C pair was removed rather than repeated. Take the number from the filament actually being supplied.