Chemical Resistance of PET/Polyester Films
PET film chemical resistance describes how an uncoated polyester carrier or a complete coated, adhesive-backed or laminated construction responds to controlled contact with acids, alkalis, solvents, cleaners and process fluids. This technical reference connects film structure, exposure conditions, mechanical and optical checks, peel behaviour and failure observations. Published data can support initial screening, but the supplied grade, actual chemical formulation, protected surface and intended dwell condition should be confirmed by sample testing. Chemical exposure data should not be treated as a penetration limit; evaluate localized loading separately with the PET film puncture resistance technical data.
Where This Data Applies – and Where It Does Not
This technical data covers uncoated BOPET, treated, hard-coated, adhesive-backed, release-coated and selected laminated structures. It supports testing where film contacts cleaners, process oils, inks, dilute acids, alkaline solutions or industrial solvents.
A bare-carrier result cannot be assigned to a complete stack. Adhesive, coating, ink, release treatment and cut edges may fail first. For material-family context, review the PET film construction options for electronics and optical converting.
Record the Film Stack Before Testing
Record PET grade, film and total thickness, appearance, treated side, coating, adhesive, liner, substrate, lot and sample age. Add MD and TD direction for tensile or elongation comparisons.
A protective stack may include PET base film + treatment or coating + pressure-sensitive adhesive + liner. Test face and exposed edge separately when liquid can reach an interface. Chemical treatment changes wetting; it does not prove chemical resistance. See the PET film surface energy testing guide for that distinction.
Reference Data for the Submitted Construction
Mark every value as typical, grade-dependent or project-confirmed. Compatibility charts support screening only. Record the formulation, concentration, temperature, contact mode, duration, control, recovery period and acceptance criteria.
Item | Typical Value / Reference Range | Test Method or Condition | Notes |
Base film | BOPET or treated PET; submitted grade | Material and lot record | Do not transfer results between grades |
Film / total thickness | Project-confirmed | Gauge at defined positions; state liner inclusion | Separate carrier thickness from total build |
Colour / clarity | Clear, tinted, printed or opaque | Controlled pre-exposure inspection | Retain an unexposed control |
Surface treatment | Untreated, corona, primer or hard coat | Side identification; dyne or coating check if relevant | Treatment is not chemical resistance |
Adhesive type | Acrylic, silicone or rubber-based, if present | Construction record | Adhesive may control practical performance |
Peel adhesion | Typical or project-confirmed | Defined substrate, angle, speed and dwell | Report the complete condition |
Tensile strength / elongation | Typical for tested grade and MD/TD | Same specimen orientation before and after exposure | Use retention versus control |
Haze / transmittance | Grade-dependent for clear structures | Optical test before and after exposure | Not applicable to opaque film |
Chemical-exposure rating | No significant change / slight / functional / severe | Chemical, concentration, temperature, time and mode | Visual rating alone is insufficient |
Edge lift / residue | Observed under stated substrate and dwell | Face, edge and removal inspection | Record affected area and removal behaviour |
Match the Method to the Contact Mode
How to test PET film chemical resistance depends on contact mode. Immersion, spot contact, repeated wiping, saturated-pad, vapour and exposed-edge testing represent different risks. A standard number is incomplete without the specimen, concentration, temperature, time and evaluation method.
ASTM D543 or a documented equivalent can guide controlled chemical exposure. ISO 175 should be referenced only when the specimen and full-surface immersion condition fall within its scope. Thin-film tensile retention, adhesive interaction and repeated wiping need additional methods.
Test Item | What It Checks | Suggested Method or Reference | Why It Matters | When To Request It |
Controlled liquid contact | Appearance, dimensions and property change | ASTM D543 or documented equivalent; ISO 175 only within scope | Basic response to a defined liquid | More than brief splash contact |
Spot / saturated pad | Local staining, softening or coating change | Controlled volume, area, temperature and time | Represents local fluid contact | Limited-area exposure |
Repeated wipe | Gloss, haze and coating durability | Defined cloth, liquid, load and cycles | Represents cleaning better than immersion | Frequently cleaned surfaces |
Exposed edge | Liquid entry into interfaces | Apply fluid at slit or die-cut edge on actual substrate | Interfaces may fail before the face | Adhesive or laminated parts |
Tensile / elongation retention | Strength and flexibility loss | ASTM D882 or equivalent | Detects hidden embrittlement | Tension, converting or removal |
Haze / transmittance | Clouding or optical loss | ASTM D1003 or equivalent | Confirms visual function | Clear optical structures |
Peel / coating adhesion | Adhesion build, transfer or layer loss | ASTM D3330, FINAT-based, cross-hatch or documented method | Links exposure to removal and layer integrity | Adhesive or coated PET |
Separate Carrier Failure from Interface Failure
Carrier failure includes swelling, softening, curl, dimensional change, cracking or reduced tensile and elongation retention. Coatings may whiten, lose gloss or detach. Adhesives may show peel change, edge lifting, cohesive failure, transfer or visible residue. The protected surface may also discolor or lift.
No visible change does not prove full retention. Compare exposed and unexposed samples from the same lot. For transparent structures, clear PET film selection guidance helps identify clarity, treated side and optical-grade variables before haze and transmittance checks.
Read Mechanical, Optical and Peel Results Together
Film thickness affects stiffness and handling, not universal compatibility. Tensile strength shows force-bearing behaviour; elongation shows deformation before failure. Lower elongation can increase tearing even when tensile strength appears acceptable.
For clear film, review haze and light transmittance together. Peel adhesion requires the substrate, dwell, angle and speed. Low adhesion can permit lift; high adhesion build can increase stretching or transfer. Repeated cleaner contact on coated displays should also be reviewed against hard-coated PET film performance factors.
Compatibility Changes with the Protected Surface
Glass, stainless steel, anodized aluminium, painted metal, acrylic, polycarbonate, coated panels, rough finishes and low-energy plastics require separate checks. Surface energy, texture, coating cure, residual oil and chemical sensitivity change wet-out and removal behaviour.
Temperature, humidity, sunlight, storage time, equipment setting and operator method affect results. Load weight, cargo shape and transport distance can add pressure, vibration, temperature cycling and longer dwell.
Use Three Dwell Gates Before Material Release
PET film sample testing before full use should reproduce the substrate, application pressure, fluid formulation, concentration, temperature and contact mode. Keep an unexposed control and use the intended equipment setting or a documented manual method.
At 24 hours, check peel behaviour, bubbles, edge lifting, distortion and adhesive trace. At 72 hours, inspect surface shadow, gloss, swelling and optical change. At 7 days, check adhesion build, tearing, residue, coating disturbance and delayed colour change. Longer storage or transport requires a matching dwell study.
Where coating, laminating, slitting, die-cutting or retained samples are required, align the trial with the film converting and quality-control capabilities that can be documented.
When a Normal Value Still Produces Failure
A normal average can hide local failure. Peel may be acceptable while edges lift; haze may pass while gloss shadow remains visible; the PET carrier may pass while adhesive transfers through a cut edge. Approval should combine measured values with inspection of the complete construction and actual substrate.
Data Point | If Too Low | If Too High | Risk in Application | Check Before Full Use |
Film thickness | Wrinkling or puncture | Poor conformity | Bubbles, lift or unstable converting | Handling and removal trial |
Peel adhesion | Premature lift | Difficult removal | Contamination entry, tearing or transfer | 24h / 72h / 7-day peel |
Tensile strength | Failure under tension | Unnecessary rigidity | Breakage or poor conformity | MD/TD retention |
Elongation | Brittleness | Excessive stretch | Tearing or distortion | Retention and removal check |
Haze | May rise after exposure | Loss of visibility | Clouding or optical rejection | Before / after optical test |
Exposure time / temperature | Delayed failure missed | Unrealistic over-test | False approval or rejection | Match actual process |
Keep Storage History with the Test Result
Store rolls in original packaging under grade-specific temperature and humidity. Avoid sunlight, uncontrolled heat, chemical vapour, roll pressure and damaged packaging. Record production date, storage time, transport condition and temperature cycling.
Condition cold or hot rolls before testing. Support cores and avoid stacking that causes telescoping, blocking or edge damage. Crushed edges, unsuitable tension, nip pressure, line speed or inconsistent application can create unrelated failure.
Technical Connections for the Next Decision
Use PET film construction options for electronics and optical converting when the stack is not yet selected. Use the PET film surface energy testing guide when the question is wetting or coating anchorage.
FAQ
How should pet film chemical resistance be evaluated for an actual process fluid?
Use the submitted construction and actual fluid at the intended concentration, temperature and contact mode. Include a control and check the properties that matter, such as appearance, tensile and elongation retention, haze, peel adhesion, edge lifting and residue.
What is the difference between a typical value and a project-confirmed value?
A typical value describes expected or previously measured behaviour under a stated method. A project-confirmed value uses an agreed specimen, condition, sampling plan, tolerance and acceptance criterion.
Can a base-film result be applied to adhesive-backed or hard-coated PET?
Not automatically. Adhesive, primer, hard coat, ink or release treatment may soften, swell, lose adhesion or change appearance before the carrier. Test the complete construction and exposed edges.
Why can the same film behave differently on glass, metal and plastic?
Surface energy, texture, coating cure, residual oil, cleaning method and sensitivity to the test fluid change wet-out, interface migration and removal behaviour.
Can storage and transport change the result?
Yes. Temperature, humidity, sunlight, roll pressure, packaging damage, storage time and transport distance can alter flatness, coating condition, adhesive behaviour and cleanliness.
