Dimensional stability. Low friction. Food-contact capable.
PET (Ertalyte) and PBT (Valox) are semicrystalline polyesters that combine the dimensional stability of Delrin with improved chemical resistance and FDA compliance. Standard for precision mechanical parts, bearings running against metal, and electrical connectors.
At a glance
- Density
- 1.39 g/cc
- Tensile strength
- 90 MPa
- Flexural modulus
- 3.1 GPa
- Elongation
- 15 %
- HDT (0.45 MPa)
- 110 °C
- Tg
- 85 °C
- Continuous service
- 100 °C
- Water absorption
- 0.2 %
Key data
- Density
- 1.39 g/cc
- Tensile strength
- 90 MPa
- Flexural modulus
- 3.1 GPa
- Elongation
- 15 %
- HDT (0.45 MPa)
- 110 °C
- Tg
- 85 °C
- Continuous service
- 100 °C
- Water absorption
- 0.2 %
PET & PBT grades.
PET (Ertalyte)
Unfilled polyethylene terephthalate. Excellent dimensional stability, low friction, FDA 21 CFR 177.1630 compliant. Food-contact bearings, precision gears, fluid-handling components.
PET-TX (Ertalyte TX)
Solid lubricant filled PET. 2× the bearing life of unfilled PET. Dry-running bearings, bushings, wear strips against metal.
PBT (Valox)
Polybutylene terephthalate. 30 °C higher continuous service than PET. Standard for electrical connector bodies, automotive under-hood, appliance internals.
PBT-GF30
30% glass-fiber reinforced PBT. Tensile 140 MPa. Structural automotive parts, tool housings, electrical backplates.
PBT Flame Retardant
FR-compounded PBT for electrical and electronics applications requiring flame rating. Standard for appliance connectors.
PET-CF
Carbon fiber reinforced PET. Improved stiffness, ESD-dissipative. Semiconductor handling fixtures, precision mechanical parts.
PET for precision mechanical, PBT for electrical and higher-temperature service. Filled variants for structural and bearing applications.
When PET or PBT is right.
Dimensional stability
0.2% water absorption — 10× better than nylon. Parts hold tolerance in humid environments. Critical for precision gears and mating components.
Low friction bearings
Coefficient of friction 0.20 (lower than Delrin at 0.25). Ertalyte TX with internal lubricant doubles bearing life. Unlubricated metal-to-plastic bearings.
FDA food contact
PET Ertalyte is FDA 21 CFR 177.1630 compliant. Standard for food processing equipment, beverage handling, pharmaceutical fluid paths.
Electrical insulation
PBT high dielectric strength (25 kV/mm). Default for automotive connector bodies, appliance electrical hardware.
These polyesters bridge gaps between Delrin (lacks FDA compliance), Nylon (absorbs water), and PEEK (premium cost). Four scenarios where PET/PBT wins decisively.
PET / PBT applications.
Precision gears
PET Ertalyte gears for quiet, dimensionally stable mechanical drives
Food processing bearings
Ertalyte TX bushings in food and beverage equipment — FDA compliant
Automotive connectors
PBT connector housings for under-hood and interior electrical — most common connector plastic
Wear strips
Ertalyte TX conveyor guides, slide bars — low friction against metal
Electrical backplates
PBT-GF30 relay sockets, circuit breaker internals
Appliance internals
PBT washing machine and dishwasher components — heat + humidity
Pump components
PET impellers, housings for pharmaceutical and food pumps
Semiconductor handling
PET-CF ESD-dissipative wafer carriers and fixtures
Precision instrument
Camera and optical instrument housings — dimensional stability
PET / PBT finishing.
As-machined
Ra 0.8 µm single-pass — better natural finish than most engineering plastics. Minimal secondary finishing needed.
Polished
Ra 0.2 µm achievable for cosmetic or low-friction surface. Rare for mechanical applications.
Laser marked
Excellent contrast on natural PET and PBT. Standard for serial numbers, part IDs.
Pad printed
Works with standard pad print inks on flat and curved PBT surfaces.
Ultrasonic welded
PBT welds well to itself and ABS. Standard for assembly without fasteners.
Bonded
Accepts cyanoacrylate and epoxy after surface cleaning. No special preparation needed for most adhesives.
Machined threads
Threads machine cleanly and hold well. For high-cycle applications, use heli-coil inserts.
Colored
Available pre-colored in black, natural, blue, red. Custom colors through compounded billet.
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Dimensional stability — questions
PET vs Delrin — how do I choose?
PET Ertalyte: FDA compliant for food contact, higher tensile strength (90 vs 70 MPa), better dimensional stability in humid conditions. Delrin (POM): better impact strength, slightly lower friction, more familiar to most engineers. For food/pharma, use PET. For general mechanical without regulatory requirements, Delrin is usually cheaper and adequate. PET is about 20–30% more expensive than Delrin.
What is the difference between PET and PBT?
Same chemical family (polyesters) with different backbone chain lengths. PET: better dimensional stability, higher tensile strength, FDA food-contact compliant. PBT: faster crystallization (better for injection molding), higher HDT (210 °C vs 110 °C for PET), superior electrical properties. PET for precision mechanical and food-contact; PBT for electrical and automotive.
Is PET suitable for bearings against metal?
Yes — one of its best applications. Ertalyte (unfilled) runs dry against 316L stainless or hardened steel shafts at PV values up to 3,000 (psi·fpm). Ertalyte TX (internal lubricant) doubles that rating. For higher loads, consider Vespel or PEEK-bearing grades. Never run PET dry against aluminum (galling).
Can PBT be welded?
Yes. PBT welds well via ultrasonic, vibration, hot-plate, and laser transmission welding. Weld strengths typically 70–90% of parent material. Ultrasonic is the most common production method for PBT connector assembly. PET also welds but less commonly used in welded assemblies.
Is PBT-GF30 suitable for structural applications?
Yes — for moderate structural loads. Tensile 140 MPa, flexural modulus 10 GPa. Common for automotive brackets, tool housings, appliance structural components. For high-load structural, consider PA66-GF30 or PEEK-GF30. PBT-GF30 sweet spot: medium-load structural parts requiring electrical insulation or chemical resistance that nylon can't match.
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