PET (Ertalyte) FAQ — Properties, Grades, Machining & Food Use

Common technical and purchasing questions about Ertalyte (bearing-grade PET-P), answered directly. For the complete material overview, see the PET (Ertalyte) material hub.

At a glance:

• Ertalyte ≠ PETG — they are chemically and structurally unrelated for engineering purposes
• Ertalyte TX adds PTFE lubrication; natural grade suits lubricated service
• FDA 21 CFR 177.1630 covers both natural and TX grades
• Moisture absorption is ~0.10% at 24 hr — 15× less than nylon 6/6
• Continuous use limit is 212°F (100°C) — use PEEK or PPS above this threshold
• Machines well on standard CNC equipment; no pre-drying required

Q1: What is the difference between Ertalyte and PETG?

Ertalyte (PET-P) and PETG are both polyethylene terephthalate derivatives, but they are engineered for entirely different applications and should never be substituted for one another.

Ertalyte (PET-P) is semi-crystalline, opaque, and produced specifically for bearing and wear applications. Its semi-crystalline structure provides high stiffness (600,000 psi flexural modulus), low friction, and dimensional stability in moisture-exposed environments. It is not transparent and cannot be thermoformed.

PETG is glycol-modified PET — amorphous (no crystalline structure), optically clear, and engineered for thermoforming and display applications. PETG has low stiffness, poor wear resistance, and a much lower heat deflection temperature (~140°F vs 185°F for Ertalyte). It is not a bearing plastic.

The confusion arises because both contain "PET" in their name. For the full technical breakdown, see the PET vs PETG comparison.

Q2: What is Ertalyte TX and when should I use it?

Ertalyte TX is PET-P compounded with PTFE and a proprietary solid lubricant (MoS₂ or graphite). The PTFE creates a transfer film on the mating metal surface that reduces friction and wear dramatically:

• Coefficient of friction drops from ~0.25 (natural) to ~0.10 (TX) against dry steel
• Wear factor K drops from ~65 to ~8 (× 10⁻¹⁰) — approximately 8× longer service life

Specify Ertalyte TX when the bearing or bushing runs dry (no external lubrication is available), when lubricant contamination of the product stream is unacceptable (food machinery, pharmaceutical), or when noise reduction from stick-slip matters.

Specify Ertalyte natural when the bearing runs lubricated (water, oil, or process fluid), when maximum mechanical strength is needed, or when the slightly translucent color assists with visual inspection.

See Ertalyte grades for the full comparison.

Q3: Is Ertalyte FDA approved for food contact?

Yes. Both Ertalyte natural and Ertalyte TX comply with FDA 21 CFR 177.1630, which covers polyethylene terephthalate resins for food-contact use. This covers direct and repeated contact with food.

USDA acceptance for incidental food contact in meat and poultry processing plants is also available.

FDA compliance is lot-specific: when ordering for a food-zone application, request a Certificate of Conformance (COC) from your supplier confirming 21 CFR 177.1630 compliance for the specific lot.

Full compliance details: PET FDA food-grade compliance.

Q4: How does Ertalyte compare to acetal (Delrin) for bearings?

Both are common bearing plastics with FDA compliance. The key differences:

• Wet environments: Ertalyte absorbs 0.10% moisture in 24 hr vs acetal's 0.22% — and at saturation, Ertalyte's dimensional change is <0.05% vs acetal's ~0.20%. In wash-down or submerged service, Ertalyte maintains its machined clearances better.
• Cost: Acetal is generally less expensive (often 30–60% cheaper per pound).
• Machinability: Acetal machines with shorter, more manageable chips. Ertalyte produces longer stringy chips requiring more attention to chip evacuation.
• Dilute acid resistance: Ertalyte performs better in the weak organic acids common in food processing (citric, acetic, phosphoric).

For dry-environment bearings with no chemical exposure, acetal (Delrin) is often the preferred cost-performance choice. For wet or food-acid environments, Ertalyte is the technically stronger selection.

Q5: What is Ertalyte's maximum operating temperature?

Continuous service limit: 212°F (100°C). Heat deflection temperature at 264 psi load: 185°F (85°C).

In bearing applications, consider that frictional heat raises the contact surface temperature above ambient. For high-speed or high-load dry bearings (particularly with unfilled Ertalyte), surface temperature at the bushing bore can be 20–40°C above ambient — which may approach the HDT in hot environments. Ertalyte TX's lower friction coefficient reduces this heat rise.

For applications requiring continuous service above 212°F, PEEK (480°F) or PPS (Ryton) (450°F) are the standard alternatives.

Q6: Does Ertalyte absorb moisture? Does it need pre-drying before machining?

Ertalyte absorbs 0.10% moisture in 24 hours at room temperature — making it one of the most moisture-stable engineering thermoplastics available. At saturation, absorption is only 0.26%, and dimensional change is less than 0.05%.

No pre-drying is required before machining. Unlike nylon, which must be dried before precision machining to prevent dimensional change during the operation, Ertalyte can be machined directly from stock without conditioning.

Machined Ertalyte parts can also be gauged immediately — no need to wait for moisture equilibration before measuring bores and dimensions.

Q7: What sizes is Ertalyte rod available in?

Ertalyte rod (natural and TX) is stocked in diameters from 0.500" through 6.0" in 4-foot lengths. Common stocked diameters include:

• 0.500", 0.750", 1.0", 1.25", 1.5", 2.0", 2.5", 3.0", 4.0", 5.0", 6.0"

Larger or intermediate diameters may be available to order. For full size tables and OD tolerances, see the PET rod page.

Q8: Can I use Ertalyte for outdoor applications?

Ertalyte's UV resistance is moderate — not recommended for prolonged direct UV exposure without a UV stabilizer. For outdoor applications, HDPE, acetal with UV stabilizer, or UV-stabilized nylon are better choices. Ertalyte is primarily an indoor industrial material.

Q9: Is Ertalyte the same as "bearing-grade PET"?

Yes. "Bearing-grade PET," "PET-P," and "Ertalyte" all refer to the same class of material — semi-crystalline, high-molecular-weight polyethylene terephthalate produced for precision machined wear parts. Ertalyte is the dominant trade name; generic PET-P from other suppliers (Rochling, Ensinger) meets the same ASTM D7292 specification.

This is distinct from bottle-grade PET (amorphous, used in beverage containers) and from PETG (glycol-modified, used in thermoforming and displays).

Q10: Does Ertalyte work as a replacement for bronze bushings?

Yes, with caveats. Ertalyte replaces bronze bushings effectively in:

• Light-to-medium loads (PV up to 3,000 ft·psi/min dry for unfilled; 10,000 for TX)
• Corrosive or food-wet environments where bronze can corrode or contaminate
• Applications requiring electrical isolation (Ertalyte is a good insulator; bronze conducts)
• Weight reduction (Ertalyte density 1.41 g/cc vs bronze ~8.5 g/cc)

Bronze remains preferable for:

• Very high load-speed products (PV > 20,000 ft·psi/min) beyond TX capability
• Elevated temperatures (>100°C)
• Applications where thermal conductivity of the bushing is needed to dissipate bearing heat

More related guides

Applications

• Bushings & Bearings
• Food Processing Components

Industries

• Food & Beverage

Compare to other materials

• PET vs. PETG
• PET vs. Acetal (Delrin)

Frequently asked questions — PET FAQ