PBT

PBT sits in the polyester filament family, supplied as filament, strip fill and tube fill, drawn in round, triangular, cross-shaped, hollow, star-shaped and hexagonal sections and set in straight rows, helical, staggered, zoned, wavy and random fill patterns.

PBT is used in custom cleaning brushes for bottle, appliance, electronics and wet-cleaning brushes that need stable stiffness after repeated water exposure.

Where a project stalls on material choice, the comparison is normally against Nylon PA, Polypropylene PP and PET Polyester, and it turns on moisture uptake and working temperature.

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

PBT is medium-firm; Shore D about 75-85; good recovery and stiffness with low water absorption, which is why PBT 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.

The published filament ranges, set against the grades it competes with. These are filament figures, not finished-brush values.

The part people get wrong: the number that decides scrubbing pressure is diameter over trim length, not the grade name. Two brushes in this material can behave nothing alike.

PBT takes up 0.05–0.20% (24h, ISO 62/ASTM D570).

Low water absorption keeps filament stiffness stable in wet cleaning.

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-industry references publish maximum working guidance from about 80–100°C for some PBT hygiene filaments up to 140°C for other polyester brush filaments. Confirm the exact filament grade and sustained-load conditions.

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 223–230°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, 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.

Often suitable with water, oils and many mild cleaning chemicals, but compatibility is grade- and chemical-specific; check cleaner identity, concentration, temperature and exposure time before specifying PBT.

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 PBT 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 0.03 mm. Below that the filament turns fragile and breaks under ordinary contact pressure, so 0.03–2.00 mm is the working range.

Free trim runs 2–250 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 0.03–0.52 mm for light wiping, dusting and surfaces that mark easily, and 0.52–2.00 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, chemical etching, silicone-oil coating, anti-static coating and antibacterial coating.

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.

Bottle, appliance, electronics and wet-cleaning brushes that need stable stiffness after repeated water exposure.

The cleaning work it is specified for most often:

• Laboratory Tube Cleaning
• CPAP Hose Cleaning
• Household Dish, Teapot & Kitchen Detail Cleaning
• Beverage Equipment Cleaning
• Food Equipment Cleaning
• Tube & Pipe Cleaning

Brush types built with this fill:

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

If the sample comes back rejected: Not for heavy rust removal or high-cutting deburring.

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 PBT 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.

Source: American Brush Manufacturers Association — Brush Lingo — polyester and PBT filament. Published PBT filament limits differ by grade wide enough that no single number describes the family, which is why this page gives a band and asks for the supplied grade instead.