Home / docs / Cnc plastic materials / Pet / PET / PETP (Polyethylene Terephthalate) CNC Machining Material Manual

PET / PETP (Polyethylene Terephthalate) CNC Machining Material Manual

Cnc plastic materials
Last updated: May 23, 2026

PET / PETP (Polyethylene Terephthalate / Ertalyte) — CNC Machining Material Manual

← Back to the Plastic Materials Handbook

Rating legend — ★★★★★ best · ★☆☆☆☆ worst. For machinability/wear/heat resistance more stars = better; for cost, fewer stars = cheaper.

📋 Material Quick-Reference Card

┌──────────────────────────────────────────┐
│  Material Name: PET / PETP                │
│  (Polyethylene Terephthalate / Ertalyte)  │
│  Category: Semi-crystalline engineering   │
│            plastic / polyester            │
│  Density: 1.39~1.41 g/cm³                 │
│  Tensile Strength: 80~90 MPa              │
│  Flexural Strength: 100~140 MPa           │
│  Hardness: M94~M105 (Rockwell M)          │
│  Melting Point: 245~255 ℃                 │
│  Machinability: ★★★★★ (excellent)         │
│  Wear Resistance: ★★★★★ (low friction)    │
│  Chemical Resistance: ★★★★☆               │
│  Cost: ★★★★☆ (higher than POM)            │
│  Keywords: precision, wear-resistant,     │
│            dimensionally stable, low      │
│            moisture absorption            │
└──────────────────────────────────────────┘

1. Material Overview

1.1 Introduction

PET / PETP (Polyethylene Terephthalate) is a high-stiffness, highly dimensionally stable, low-friction semi-crystalline engineering plastic. In CNC machining, the common machine-grade material is PET-P, widely known by the trade name Ertalyte. It is selected when parts require tight tolerance, excellent wear resistance, and very low moisture absorption.

Compared with POM, PET-P is generally stiffer, more dimensionally stable, and often better for precision wear parts, but it is also more brittle and more notch-sensitive, so sharp corners and impact-loaded features require more careful design.

  • English Name: Polyethylene Terephthalate / PET / PETP / PET-P
  • Common Nicknames: PET-P, PETP, machine-grade PET, polyester engineering plastic
  • Famous Brand Names: Ertalyte, Ertalyte TX (PTFE-filled PET-P), Sustadur PET

1.2 Common Types ⭐ Important

Type Full Name Characteristics
Unfilled PET-P Machine-grade PET / Ertalyte Excellent machinability, high stiffness, very low moisture absorption, good wear resistance ⭐ Common for CNC
PTFE-filled PET-P Ertalyte TX / PET-P TX Lower friction, improved wear behavior, better sliding performance; slightly lower strength/stiffness than unfilled PET-P
Food / medical grades FDA / medical-compliant PET-P Used for food contact, medical fixtures, and clean mechanical parts where certified stock is required

💡 Machine-grade PET-P is different from bottle-grade PET. For CNC parts, choose extruded or compression-molded engineering stock designed for machining, such as Ertalyte or equivalent PET-P rod/plate.

1.3 Raw Material Forms

Common forms for CNC machining:

  • PET-P Rod (round bar): bushings, bearings, rollers, shafts, turned precision parts
  • PET-P Sheet/Plate: milled parts, insulating plates, guides, wear pads
  • Common colors: natural white/off-white, black; Ertalyte TX is often light grey

2. Composition & Physical Properties

2.1 Material Composition

PET is a thermoplastic polyester formed from terephthalic acid and ethylene glycol. Machine-grade PET-P has a semi-crystalline structure, giving it high hardness, stiffness, creep resistance, dimensional stability, and excellent wear performance.

Type Molecular / Material Structure
Unfilled PET-P Semi-crystalline polyester, high stiffness and low moisture absorption
PTFE-filled PET-P PET-P matrix with PTFE solid-lubricant filler for lower friction and improved wear

2.2 Physical Properties

Property Value
Density 1.39~1.41 g/cm³
Melting Point 245~255 ℃
Heat Deflection Temp. 70~80 ℃ (some grades higher)
Long-term Service Temp. -20~100/115 ℃
Thermal Conductivity 0.24~0.30 W/(m·K)
Water Absorption 0.1~0.3% (very low)
Coefficient of Thermal Expansion 60~80×10⁻⁶ /℃

💡 PET-P has very low moisture absorption, so its machined dimensions remain stable in normal humidity. This is one of its biggest advantages over nylon and an important advantage over many general engineering plastics.

3. Mechanical & Chemical Properties

3.1 Mechanical Properties

Property Value
Tensile Strength 80~90 MPa
Flexural Strength 100~140 MPa
Elastic Modulus 3000~3500 MPa
Elongation 8~20%
Hardness M94~M105 (Rockwell M)
Impact Strength Fair; more brittle/notch-sensitive than POM
Coefficient of Friction 0.15~0.25 (low; lower with PTFE-filled grades)

⚠️ PET-P is stiff and precise, but it is less forgiving than POM under impact or sharp-notch loading. Avoid sharp internal corners, thin unsupported tabs, and aggressive press fits.

3.2 Chemical Resistance

Medium Resistance
Dilute acids ✅ Good
Oils, greases, fuels ✅ Excellent
Many organic solvents ✅ Good
Strong acids ❌ Poor
Strong bases / alkalis ❌ Poor
Hot water / steam ❌ Poor; hydrolysis risk
Some chlorinated solvents ⚠️ Fair to poor; verify grade compatibility

3.3 Notable Characteristics

  • Excellent dimensional stability: very low moisture absorption and low thermal expansion for a plastic
  • High stiffness and good creep resistance: holds shape well under long-term load
  • Excellent wear resistance and low friction: suitable for bearings, bushings, sliding guides, and gears
  • Good fatigue resistance: performs well in repeated motion when stress concentrations are controlled
  • Good electrical insulation
  • More brittle/notch-sensitive than POM: design radii and edge protection are important

4. CNC Machining Process ⭐⭐ Core

4.1 Machinability Rating

★★★★★ Excellent machinability — PET-P machines very well and is commonly used for high-precision plastic components:

  • Clean cutting with sharp tools and good chip evacuation
  • Fine surface finish, often suitable directly after machining
  • High dimensional accuracy, achievable to ±0.01mm with stable stock, fixturing, and process control
  • Excellent for tight-tolerance parts requiring wear resistance and dimensional stability
  • More brittle than POM, so edges and small features must be protected from chipping
Item Recommendation
Tool Material Carbide preferred; sharp HSS acceptable for simple work
Cutting Edge Very sharp, polished edge to reduce heat and prevent edge chipping
Rake Angle Positive rake angle (10°~20°)
Helix Angle Medium-to-large helix for smooth chip evacuation
Flutes 1~3 flutes; use large chip pockets for milling and routing
Operation Spindle Speed (RPM) Feed Rate (mm/min) Depth of Cut (mm)
Rough Milling 5000~10000 1000~2500 1~3
Finish Milling 8000~16000 600~1500 0.1~0.5
Turning 1500~3000 0.05~0.25/rev 0.3~2
Drilling 1000~3000 40~180 —

📌 Parameters are for reference only; adjust based on machine rigidity, tool diameter, workholding, grade, and part geometry.

4.4 Machining Challenges & Solutions

Challenge Cause Solution
Edge chipping PET-P is stiffer and more brittle than POM Use sharp tools, positive rake, climb milling where appropriate, add chamfers/radii
Notch cracking Sharp internal corners, press fits, sudden section changes Add internal radii, avoid sharp grooves, use controlled fits
Thermal deformation Plastic has low thermal conductivity; dull tools generate heat Use sharp tools, air blast, light finishing cuts, avoid rubbing
Internal stress release distortion Residual stress in rod/plate stock Stress relieve before precision finishing; rough machine symmetrically
Drill breakout cracking Low support at exit side, excessive feed Back up the hole, peck drill, reduce feed near breakthrough
Thin-wall chatter High stiffness but limited damping and low section rigidity Improve support, reduce depth of cut, use sharp tools and balanced toolpaths

4.5 Stress-Relief Recommendation ⭐

To reduce machining distortion and improve precision, stress relief is recommended before/after machining high-tolerance PET-P parts:

Reference Stress-Relief Process:
• Temperature: 120~140 ℃
• Time: approx. 30~60 min per 25mm of wall thickness
• Cooling: slow furnace cooling to room temperature

💡 For high-precision PET-P parts, the rough machining → stress relief → finish machining workflow helps maintain ±0.01mm-class tolerance and reduces post-machining movement.

4.6 Cooling Methods

  • Air cooling: preferred for most PET-P machining; keeps chips clear and avoids moisture/chemical issues
  • Mist / water-soluble coolant: usable for precision work if compatible with the grade and cleaned afterward
  • ❌ Avoid excessive heat, dull tools, and long rubbing cuts
  • ❌ Avoid hot-water or steam exposure after machining when dimensional stability and strength are critical

5. Surface Treatment

PET-P generally machines to a clean, smooth surface, but like many engineering plastics, it has limited decorative finishing options compared with ABS or PC:

Process Feasibility Notes
Polishing ✅ Good Fine machined finish is easy; mirror finish possible with proper technique
Mechanical texturing / sandblasting ✅ Feasible Use light pressure to avoid edge damage and uneven texture
Laser marking ✅ Feasible Common for identification; test contrast by color/grade
Screen printing ⚠️ Requires pretreatment Adhesion may require flame/plasma/corona treatment and compatible ink
Painting / electroplating ❌ Difficult Poor adhesion without special pretreatment; not a preferred PET-P finish
Dyeing ⚠️ Limited Usually specified by raw stock color rather than dyed after machining

💡 PET-P is normally used as a functional precision plastic, not a decorative plastic. If painting, plating, or cosmetic color matching is important, choose ABS, PC, or another surface-treatment-friendly material.

6. Applications & Material Selection

6.1 Typical Application Industries

Industry Application Parts
Precision mechanisms Bearings, bushings, rollers, spacers, sliding blocks
Mechanical transmission Gears, cams, guides, wear strips, low-friction parts
Automation equipment Locating parts, fixtures, conveyor wear components, guide rails
Electrical / electronics Insulators, terminal components, precision dielectric parts
Food machinery FDA-grade wear parts, rollers, guides, contact components
Medical devices Precision fixtures, non-implant mechanical components, instrument parts
Semiconductor equipment Wafer handling parts, low-moisture precision components, clean fixtures

6.2 Pros & Cons Summary

✅ Advantages ❌ Disadvantages
Excellent CNC machinability and fine surface finish More brittle and notch-sensitive than POM
Very high dimensional stability, very low moisture absorption Lower impact toughness than POM/nylon/PC
High stiffness and good creep resistance Sensitive to strong acids, bases, hot water, and steam
Excellent wear resistance and low friction Limited decorative surface treatment options
Better precision/wear performance than POM in many sliding applications Higher cost than POM
Good resistance to oils, greases, and many solvents Flammable; melts/drips when burning

6.3 Material Selection Guide

✔ Recommended for PET-P:

  • Precision parts requiring tight tolerance, low moisture absorption, and excellent dimensional stability
  • Wear parts requiring low friction and good service life (bearings, bushings, sliders, rollers)
  • Parts where PET-P’s stiffness and creep resistance are more important than impact toughness
  • Electrical insulators and semiconductor handling parts requiring stable, clean machining
  • Food and medical mechanical components when certified FDA/medical grades are specified
  • Applications where POM is close but a stiffer, more dimensionally stable, lower-wear material is preferred

✘ Not recommended for:

  • High-impact or snap-fit parts → choose POM, PA, or PC
  • Sharp-notched or heavily press-fit designs → redesign with radii/clearance or choose tougher material
  • Hot water / steam service → choose PPSU, PEEK, or suitable high-temperature polymers
  • Strong acid / strong base exposure → choose PTFE, PVDF, or compatible fluoropolymers
  • High-temperature continuous service above ~115℃ → choose PEEK, PPS, PTFE, or PI
  • Parts needing painting or electroplating → choose ABS or PC

⚠️ Safety & Handling Notes

Hazard Detail Precaution
Dust combustion Fine PET-P dust can be combustible if accumulated Use dust extraction, clean machines regularly, avoid dust clouds near ignition sources
Dust inhalation Fine machining dust may irritate the respiratory tract Use extraction; wear a mask/respirator for prolonged dry machining
Flammability PET-P is flammable and can melt/drip when burning Keep away from open flame; do not allow chips to contact hot surfaces
Overheating Dull tools and rubbing cuts can melt the surface and create fumes Use sharp tools, air blast, correct feed, and good chip evacuation
Hydrolysis Hot water, steam, strong acids, and strong bases can degrade PET-P Avoid steam sterilization and hot-water service unless the grade is verified suitable
Storage Low moisture absorption, but clean dry stock machines best Store dry, flat, indoors, away from heat, UV, and chemical contamination

⚠️ Do not treat PET-P as a steam-resistant plastic. Its normal moisture absorption is very low, but hot water and steam can cause hydrolysis, reducing strength and dimensional reliability.

🔗 Related Pages