PET vs PI vs PP – Which Label Material Is Right for Your Application?
PET, PI, or PP? Compare temperature range, chemical resistance, flexibility, and cost. Learn which synthetic label material suits your environment.
PET vs PI vs PP – Which Label Material Is Right for Your Application?
You’ve selected a high‑quality thermal transfer printer and a reliable ribbon. But if the label material doesn’t match your environment, the barcode will fail – it may delaminate in the cold, melt in the heat, or dissolve when wiped with a solvent.
Three synthetic label stocks dominate industrial applications: PET (polyester), PI (polyimide), and PP (polypropylene). Each has a unique balance of temperature resistance, chemical compatibility, flexibility, and cost.
In this guide, I’ll break down the differences, give you a side‑by‑side comparison, and help you choose the right material for your specific application – from PCB reflow soldering to food packaging and outdoor logistics.
1. PET (Polyester) Labels – The Industrial Workhorse
What it is:
PET (polyethylene terephthalate) is a rigid, durable polyester film. It’s the most common synthetic label material because it offers great all‑round performance at a reasonable price.
Key properties:
- Temperature range: -20°C to +120°C (-4°F to +248°F) – stable for most warehouses, production lines, and outdoor use (UV‑stabilised grades available).
- Chemical resistance: Good against oils, greases, mild acids, and many solvents (alcohol, IPA). Not recommended for strong solvents like acetone or MEK over long periods.
- Mechanical strength: Excellent tear and scratch resistance – survives conveyor belts, handling, and wiping.
- Flexibility: Rigid; not suitable for very tight curves or small diameter tubes.
Best applications:
- Electronics housings (laptops, servers, appliances)
- Asset tags and equipment nameplates
- Logistics totes and reusable containers
- Cosmetic bottles (with curved but not extreme surfaces)
- Automotive parts (non‑engine bay, moderate heat)
Pros:
- ✅ Good balance of durability and cost
- ✅ Works with wax/resin or resin ribbons
- ✅ Printable with fine text and high‑density barcodes
- ✅ Available in white, silver, clear, and custom colours
Cons:
- ❌ Not for reflow soldering or extreme heat (>120°C)
- ❌ Not flexible enough for very small diameters (<10mm)
- ❌ Requires resin ribbon for strong solvent resistance
Verdict: Choose PET for 90% of general industrial, logistics, and electronics labelling needs. It’s the default synthetic label – reliable and affordable.
2. PI (Polyimide) Labels – The High‑Heat Champion
What it is:
PI (polyimide) is a high‑performance polymer famous for surviving extreme temperatures. It’s amber‑coloured, very thin (25–50µm), and often used where no other label works.
Key properties:
- Temperature range: -70°C to +300°C (-94°F to +572°F) – short‑term peaks up to 340°C. Survives lead‑free reflow soldering (260°C+).
- Chemical resistance: Outstanding – resists most solvents, acids, flux residues, and cleaning agents.
- Mechanical strength: Very thin but tough; does not tear easily.
- Flexibility: Although the film is thin, it’s not elastic. However, the low thickness allows it to conform to mildly curved surfaces.
Best applications:
- PCB tracking through reflow soldering (SMT, wave soldering)
- IC trays, carrier tapes, and component reels that go through baking cycles
- Motor windings, transformer insulation, battery cells (high heat)
- Aerospace and automotive electronics (engine control modules, sensors)
Pros:
- ✅ Withstands reflow soldering – the only material for that job
- ✅ Superior chemical resistance (acetone, MEK, toluene, acids)
- ✅ Ultra‑thin (25µm) – does not interfere with component placement
- ✅ Remains legible after multiple thermal cycles
Cons:
- ❌ Expensive – often 5–10× the cost of PET
- ❌ Requires resin ribbon (wax/resin will fail)
- ❌ Overkill for room‑temperature or low‑heat applications
- ❌ Limited colour options (amber standard; white available at higher cost)
Verdict: Only use PI when you must survive reflow soldering (>200°C) or aggressive chemical immersion. For any other use, PET or PP will be more cost‑effective.
3. PP (Polypropylene) Labels – Flexible & Eco‑Friendly
What it is:
PP (polypropylene) synthetic paper is a soft, flexible, tear‑resistant material. It’s often used as an alternative to paper for waterproof, durable labels on curved surfaces.
Key properties:
- Temperature range: -20°C to +80°C (-4°F to +176°F). Not for freezing below -20°C or high heat.
- Chemical resistance: Good against water, oils, mild acids and bases. Not for strong solvents (acetone, MEK, toluene).
- Mechanical strength: Tear‑resistant but can be torn with force. Very flexible – wraps around small diameter bottles, tubes, and drums.
- Flexibility: Excellent – the most flexible of the three. Ideal for curved surfaces.
Best applications:
- Food & beverage packaging (juice bottles, dairy containers, labels on flexible pouches)
- Cosmetic tubes and squeezable bottles
- Outdoor cartons and shipping boxes (waterproof)
- Chemical drums (mild chemicals only – not for strong solvents)
- Reusable totes and containers that need a soft label
Pros:
- ✅ Very flexible – conforms to curved surfaces without lifting
- ✅ Waterproof and tear‑resistant (much tougher than paper)
- ✅ Eco‑friendly – 100% recyclable, free from PVC and chlorine
- ✅ Lower cost than PET
- ✅ Works with wax/resin or resin ribbon
Cons:
- ❌ Lower temperature limit than PET (80°C vs 120°C)
- ❌ Not for strong solvents or long‑term outdoor UV (unless specially coated)
- ❌ Less rigid – may not be suitable for very small, high‑precision die‑cut shapes
Verdict: Choose PP when you need flexibility for curved surfaces and a waterproof, eco‑friendly label, and the environment is not extremely hot or chemically aggressive.
4. Side‑by‑Side Comparison Table
| Property | PET (Polyester) | PI (Polyimide) | PP (Polypropylene) |
|---|---|---|---|
| Max continuous temp | 120°C (248°F) | 260°C+ (500°F+) | 80°C (176°F) |
| Min temp | -20°C (-4°F) | -70°C (-94°F) | -20°C (-4°F) |
| Flexibility | Rigid | Thin but not elastic | Very flexible |
| Solvent resistance | Moderate | Excellent | Moderate (better than paper) |
| Chemical resistance (strong) | Poor (acetone/MEK attack) | Excellent | Poor |
| Tear resistance | Excellent | Excellent | Good |
| Waterproof | Yes | Yes | Yes |
| Recyclable | Mixed (often downcycled) | Limited | 100% recyclable |
| Relative cost | $$ | $$$$ | $ |
| Recommended ribbon | Wax/resin or resin | Resin only | Wax/resin or resin |
| Best use case | General industrial, electronics, logistics | PCB reflow soldering, extreme heat | Curved surfaces, food packaging, eco‑labels |
5. How to Choose – Decision Guide
Ask these questions in order:
- Will the label go through reflow soldering (>200°C)?
Yes → PI (no other material works). No → Continue. - Is the surface highly curved (e.g., small bottle, tube, flexible pouch)?
Yes → PP (flexibility is key). No → Continue. - Will the label be exposed to strong solvents (acetone, MEK, toluene, xylene)?
Yes → PI (or specialised chemical‑resistant PET with heavy coating – test first). No → Continue. - What is the maximum temperature the label will face (after printing)?
>120°C → PI.
80°C to 120°C → PET (PP cannot go above 80°C).
<80°C → PET or PP (choose based on flexibility and cost). - Do you need eco‑friendly / recyclable material?
Yes → PP (100% recyclable) or PET (less ideal). No → PET or PI as needed.
Summary decision matrix:
| Requirement | Recommended material |
|---|---|
| Reflow soldering (>200°C) | PI |
| Strong solvents (acetone, MEK) | PI or tested chemical‑grade PET |
| High flexibility / curved surface | PP |
| High temperature (80–120°C) | PET |
| Low cost + waterproof + flexible | PP |
| General industrial, rigid surface | PET |
6. Common Misconceptions
❌ “PI is always better because it withstands more.”
PI is expensive overkill for room‑temperature or low‑heat applications. Use PET or PP and save money.
❌ “PP is just waterproof paper.”
PP synthetic paper is much tougher – it doesn’t tear like paper and resists oils. It’s a true synthetic label.
❌ “PET cannot resist any chemicals.”
PET resists many oils, alcohols, and mild acids. It only fails against strong solvents like acetone over long periods.
❌ “All synthetic labels are the same.”
Different polymers have very different temperature limits, flexibility, and chemical compatibility – choosing wrong leads to delamination or barcode loss.
7. Conclusion & Next Steps
- PET = rigid, durable, up to 120°C – best for general industry, electronics, logistics.
- PI = extreme heat (260°C+) and strong chemicals – mandatory for reflow soldering.
- PP = flexible, eco‑friendly, up to 80°C – ideal for curved surfaces and food packaging.
Still unsure? We can help you decide. Send us:
- Your maximum and minimum temperature
- The chemicals the label will contact (if any)
- The surface material and curvature
We’ll recommend the right material and send 5–10 free samples for you to test on your own printer.
