Overview
PET-P (semi-crystalline extruded PET) is the engineering polyester stock-shape material — and Ertalyte (Quadrant’s brand) is so dominant in this category that “Ertalyte” and “PET-P” are often used interchangeably. It’s the high-strength, dimensionally-stable, FDA- compliant machined plastic for food, beverage, packaging, and precision-mechanical applications.
The position of PET-P in the engineering plastic hierarchy:
| Property | POM-C | PA66 (dry) | PET-P | PBT GF30 | PEEK |
|---|---|---|---|---|---|
| Tensile strength (MPa) | 67 | 80 | 85 | 130 | 95 |
| Flexural modulus (GPa) | 2.5 | 2.9 | 3.4 | 9.0 | 3.9 |
| HDT 1.82 MPa (°C) | 110 | 85 | 115 | 200 | 160 |
| Moisture (saturation) | 0.8% | 8.5% | 0.6% | 0.4% | 0.5% |
| Notched Izod (J/m) | 70 | 55 | 27 | 75 | 65 |
| Cost ($/lb) | 3.20 | 3.00 | 6.50 | 2.50 | 49.00 |
PET-P slots in as the higher-strength, more dimensionally-stable alternative to POM-C, at a meaningful cost premium. It’s not as tough (the lower Izod is significant) and it’s not as universally machinable, but its stiffness, strength, and dimensional stability make it the right choice for tighter-tolerance precision parts.
When PET-P specifically
The narrower question — when do you pick PET-P over POM-C or PA66?
- Higher strength than POM-C is needed. PET-P tensile is ~30% higher than POM-C; flexural modulus is ~35% higher.
- Tight tolerances must hold across humidity cycles. Better than nylon dramatically; comparable to POM but with higher stiffness.
- FDA compliance is needed. PET-P natural and black are both FDA- compliant; POM and PA66 FDA are more limited.
- Better wear behavior than POM is needed (especially with TX). Ertalyte TX (PTFE-lubricated) has higher limiting PV than POM HPV13.
- You’re machining precision bushings, gears, or wear parts in the food/beverage/packaging machinery space — PET-P is the industry-standard material.
For everything else (impact-critical, hot-water service, lowest-cost), POM-C or PA66 is typically the better default.
Machining notes
PET-P (Ertalyte) is among the best engineering plastics for machining to tight tolerances. Practical recipe:
- Sharp carbide or HSS, positive rake
- Speed: 400–1000 SFM
- Feed: 0.005–0.015 in/rev
- Coolant: optional for light cuts, recommended for heavy machining
PET-P-specific machining considerations:
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Low moisture absorption = no conditioning compensation. Like POM and unlike nylon, Ertalyte parts don’t shift dimensionally between machining and customer delivery. This is a major workflow advantage for tight-tolerance precision parts.
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Low CTE = minimal thermal drift during machining. PET-P has 60–80 µm/m·°C, lower than POM (110) or PA66 (90). Heavy machining doesn’t generate the dimensional drift that POM can show.
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Notch sensitivity matters. Ertalyte is meaningfully more brittle than POM or PA66 (Izod ~27 J/m vs POM ~70). Generously radius internal corners, avoid sharp stress concentrations, and handle parts carefully — small flaws can propagate as cracks under load.
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Ertalyte TX is even more brittle. The PTFE-lubricated grade has higher hardness and lower elongation than natural Ertalyte. Bearing-grade applications work well; impact-loaded structural parts don’t.
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Bonding is poor. Like POM and PBT, PET-P requires surface activation (plasma, flame, or chromic acid etch) for adhesive bonding. Plan for mechanical fasteners or ultrasonic welding.
Variant selection guidance
- Ertalyte Natural — the default for precision machined parts in food, beverage, and packaging machinery. FDA-compliant. The property data above represents this variant.
- Ertalyte Black — same properties as natural, with the unusual FDA-compliant-in-black status. Used where visual contrast with product matters or where light protection helps.
- Ertalyte TX (PTFE-lubricated) — bearings, bushings, wear components. Coefficient of friction 0.10, limiting PV ~3× POM HPV13. Use when POM HPV13 isn’t quite stiff enough.
- Ertalyte MD (metal-detectable) — food-industry standard for parts that could fragment. Blue color, FDA-compliant.
- Ertalyte EC (static-dissipative) — semiconductor and electronics handling. Black, surface resistivity 10⁶–10⁹ Ω/sq.
PET-P vs PBT — the two engineering polyesters
PET-P and PBT share the same ester chemistry but are commercially distinct materials. Key differences:
| Property | PET-P (Ertalyte) | PBT (Crastin/Valox) |
|---|---|---|
| Crystallization speed | Slow | Fast |
| Stock shape availability | Excellent (Ertalyte) | Limited |
| Injection molding | Difficult | Excellent |
| Tensile strength (MPa) | 85 | 55 unfilled / 130 GF30 |
| Flexural modulus (GPa) | 3.4 | 2.6 unfilled / 9 GF30 |
| Max service temp (°C) | 100 | 120 |
| Typical use | Machined stock-shape parts | Injection-molded electrical |
| Dominant industry | Food/beverage machinery | Automotive electrical |
The simple rule: PET-P for machined precision parts, PBT for high-volume molded electrical connectors.
Failure modes worth designing around
Notch sensitivity is PET-P’s biggest design trap. Ertalyte has Izod ~27 J/m vs POM’s 70 J/m — meaningfully more brittle. A sharp internal corner on a highly-loaded PET-P part will propagate cracks where the same geometry in POM or PA66 would just yield. Generously radius all stress concentrations.
Hot-water hydrolysis — like PBT, PET-P’s ester backbone degrades in hot water above 65°C. Not for continuous hot-water service. POM-C handles 80°C+ continuous; PET-P doesn’t.
Base attack — strong alkaline cleaners attack the ester backbone. Avoid hot caustic, especially with NaOH or KOH-based sanitation systems. This affects food-processing applications: verify the cleaning chemistry before specifying PET-P.
Low-temperature embrittlement below -20°C — PET-P becomes brittle. Not for cold outdoor or freezer applications where impact loading matters.
UV degradation — yellows and surface-degrades in continuous outdoor exposure. Black Ertalyte has some carbon-pigment protection but isn’t formally UV-stabilized.
Acid attack at high concentrations or temperatures. PET-P handles dilute acids better than nylon but worse than POM or PEEK. Avoid sustained strong acid exposure.
Applications by industry
- Food and beverage processing (the #1 PET-P application) — conveyor wear strips, idler wheels, bushings for bottling and canning lines, dosing components, capping heads, neck guides, metering parts. FDA-compliant in both natural and black colors.
- Packaging machinery — gear components, cam followers, wear guides, alignment fixtures. Precision tolerances and FDA compliance are typical drivers.
- Beverage and bottling — bottle handling components, neck guides, fill nozzles, capping heads. PET-P is essentially the industry standard for plastic bottling-equipment wear parts.
- Pharmaceutical processing — dosing components, fixture jigs, machined parts where FDA compliance and dimensional stability matter.
- Industrial machinery — precision bushings, gears, wear pads in higher-load applications than POM handles. Ertalyte TX for self-lubricating bearings.
- Semiconductor (specialty) — wafer carriers, alignment fixtures, static-dissipative parts (Ertalyte EC). Less common than ESD-PEEK or specialty PEI.
- Dairy and meat processing — wear parts, fittings, conveyor components. FDA + USDA + 3A-Dairy compliance available.
- General engineering tooling — precision fixture parts, gages, reference surfaces. Dimensional stability and machinability are the selling points.
- Electronics handling — static-dissipative grades for semiconductor and electronics manufacturing.