Start with a named hardcoated PET construction for repeated actuation or an unsettled cleaner list. Consider a named PC grade for deep forming, thicker decorative parts, or exceptionally low-haze windows. Validate the complete printed and bonded stack.
1. Quick Verdict — At a Glance
Polyester is the stronger starting point when cyclic flex dominates. Polycarbonate is the stronger starting point when forming depth, a thick self-supporting film, or a very clear gloss window dominates. “Starting point” matters: a hardcoat can change abrasion and chemical behavior, while a weatherable cap layer can change outdoor behavior.
| Project condition | PET starting point | PC starting point | No generic winner |
|---|---|---|---|
| Repeated flex over embossed switch zones | ✓ | ||
| Deep 3D forming or film-insert molding | ✓ | ||
| Lowest haze in the paired gloss-grade data | ✓ | ||
| Stylus, glove, or cleaning abrasion | ✓ — compare the hardcoat | ||
| Undefined aggressive cleaner set | ✓ | ||
| Permanent outdoor or marine exposure | ✓ — specify a weatherable grade | ||
| Thick decorative or structural film | ✓ | ||
| Flame or enclosure ingress requirement | ✓ — verify the exact grade and assembly |
The paired MacDermid Alpha sheets illustrate the boundary. The Autoflex EB technical data sheet covers a hardcoated PET family with a published supplier switch result; the Autoflex PC technical data sheet covers a hardcoated PC family with lower reported gloss haze and thicker listed gauges. Those facts belong to the named products, not every PET or PC film. Teams defining custom graphic overlays should lock the grade, gauge, finish, hardcoat, print system, and adhesive as one construction before comparing samples.
2. What Graphic Overlay Material Selection Actually Compares
Graphic overlay material selection covers a laminate, not a naked polymer film. The operator touches a finish or hardcoat; the eye looks through that finish, the base film, and any printed window layers; the adhesive then couples the overlay to a housing or membrane-switch stack.
Operator / cleaning cloth / sunlight
↓
[1] First-surface hardcoat, gloss, antiglare, or texture
[2] PET or PC base film — named grade and gauge
[3] Second-surface legends, colors, dead-front inks, and clear windows
[4] Pressure-sensitive adhesive or spacer pattern
[5] Housing, display, or complete membrane-switch assembly
This stack explains why “polyester versus polycarbonate” answers often conflict. A general-purpose film such as Mylar A is base PET. Autoflex EB is PET with a chemically bonded UV-cured hard surface and a specified print-side primer. Autoflex PC is a similarly defined PC construction. The Covestro Makrofol selector goes further: it separates standard PC, UV-stabilized PC, scratch-resistant PC, optical grades, light-management grades, blends, and flame-retardant grades. Interchanging those labels erases the properties that matter.
Six drawing fields prevent material ambiguity
- Supplier and exact grade: “hardcoated PET” is incomplete; “MacDermid Alpha Autoflex EBG183” identifies the family, gloss finish, 180 µm gauge, and primer variant.
- Nominal gauge and tolerance: gauge changes stiffness, forming behavior, optical path, key feel, and fatigue results. The 2021 LEXAN 8010 sheet, for example, reports 130 MIT double folds at 0.25 mm and 35 at 0.50 mm. Those are material-fold results, not switch-actuation life.
- First-surface construction: record gloss, antiglare, texture, hardcoat, selective texture, and any clear-window treatment.
- Print system: identify second-surface primer, ink family, cure process, color stack, dead-front layers, and window ink.
- Adhesive and mating surface: name the adhesive, housing material, surface finish, curvature, cut edges, vents, and seal geometry.
- Acceptance tests: tie the drawing revision to chemical, abrasion, optical, weathering, adhesion, and actuation criteria.
An overlay film does not carry an enclosure rating by itself. IEC 60529 classifies protection provided by the enclosure; water entry can depend on adhesive coverage, seams, vent paths, cutouts, housing flatness, and assembly pressure. The same logic applies to durability: a supplier's loose-film value screens a candidate, while the printed and bonded assembly closes the decision.
3. Polyester vs Polycarbonate Graphic Overlay: Supplier-Grade Data
The cleanest side-by-side comparison uses two current data sheets from the same film supplier. MacDermid Alpha's Autoflex EB PET and Autoflex PC families share gloss and antiglare formats and several reporting methods, reducing—but not eliminating—test mismatch.
| Published field | Autoflex EB hardcoated PET | Autoflex PC hardcoated PC |
|---|---|---|
| TDS revision | CPI-00025/12, 9 Jan 2023 | CPI-00022/10, 23 Dec 2022 |
| Construction | PET plus embossable, texturable, UV-cured hard surface | PC plus chemically bonded, UV-cured hard surface |
| Listed finishes | Gloss; antiglare | Gloss; antiglare |
| Listed gauges | 130, 180, 250 µm | 180, 250, 380, 480 µm |
| Gloss haze, ASTM D1003 | <2% | <0.3% |
| Antiglare haze, ASTM D1003 | 9.8% ±3% at 130/180 µm; 10.8% ±3% at 250 µm | 10.8% ±3% |
| Total luminous transmission, ASTM D1003 | 91% ±2% | 92% ±2% |
| 60° gloss / antiglare level | 96 ±2 GU / 50 ±5 GU | 93 ±2 GU / 50 ±5 GU |
| Pencil hardness, supplier Method 058 | 2–3H | HB |
| Taber result for gloss, supplier Method 103 | <5%; detailed setup not public in TDS | <5%; detailed setup not public in TDS |
| Switch life | >5 million actuations, supplier Method 003 | Not stated in the cited TDS |
| Tensile strength at break, ASTM D882 | 172 N/mm²; base-film literature | ≥60 N/mm²; base-film literature |
| Supplier use-temperature guidance | −40°C minimum; 85°C at <10% RH; 60°C at 10–95% RH | −40°C minimum; 85°C at <10% RH; 60°C at 10–95% RH |
These are supplier-reported typical or guidance values for lab-produced film samples. They are not JASPER test results, purchase tolerances, or guarantees for printed overlays.
Three details change the verdict:
- Haze and transmission answer different questions. ASTM D1003-21 measures both; a film can transmit substantial light while scattering enough of it to blur a display. In the paired gloss data, PC has the lower reported haze. In antiglare form, both are intentionally hazier.
- Pencil hardness is a relative coating screen. ASTM D3363-22 warns that pencil manufacturer, batch, and substrate affect the result. The 2–3H versus HB difference supports PET as the harder coating within this supplier family; it does not predict wipe life.
- “Taber <5%” is not a complete abrasion specification. ASTM D1044-24 requires a controlled abrasion setup and measures the change in haze. Without wheel, load, cycle count, conditioning, cure state, and measurement geometry, the two supplier rows cannot prove equal field wear.
The side-by-side data support a disciplined conclusion: PC leads this clear-window comparison; PET leads the published flex and coating-hardness comparison. Everything else needs use-condition testing.
4. Where Polyester Wins
A hardcoated polyester control panel overlay earns the first prototype when the dominant unknown is repeated flex, cleaner exposure, or surface marking. That is a screening recommendation, not a claim that every PET grade wins.
4.1 Repeated switch flex favors a qualified PET construction
MacDermid Alpha reports more than 5 million actuations for Autoflex EB under its internal Method 003. The same figure appears for the weatherable, textured Autotex XE family. The useful fact is that named hardcoated PET films have published flex-screening data; the missing fact is the complete fixture and the behavior of the finished key.
ASTM F1578-24 covers depressing and releasing a membrane switch to a predetermined cycle count. A project test still needs the overlay gauge, emboss geometry, spacer opening, actuator diameter and hardness, stroke or force, rate, temperature, electrical load if used, and failure definition. Ink cracking, hardcoat crazing, loss of tactile force, and electrical contact failure are different endpoints. A loose-film number cannot settle all four.
4.2 PET is the conservative screen when the cleaner list is not settled
The paired MacDermid sheets describe Autoflex EB's chemical resistance as “excellent” and Autoflex PC's hardcoat resistance as “good,” but neither adjective replaces a cleaner matrix. A more useful example is Tekra's Marnot Advanced LI heat-stabilized PET sheet. Its as-manufactured hardcoated surface passed listed one- and four-hour contacts at 23°C with chemicals including acetone, MEK, isopropyl alcohol, toluene, and brake fluid. A second table reports passes after 24 hours at both 23°C and 50°C for listed cleaners, 20% bleach, SPF 70+ sunscreen, and 25% DEET.
Those passes qualify that Tekra surface under those conditions. They do not qualify printed legends, adhesive, die-cut edges, window coatings, or a stressed emboss. ASTM D543-21 makes the same boundary explicit: reagent, concentration, contact mode, duration, temperature, applied strain, and measured property must resemble the end use.
4.3 A harder PET coating can reduce cosmetic risk
Within the paired Autoflex data, the PET hardcoat reports 2–3H under supplier Method 058, versus HB for PC. That makes PET the sensible first sample for stylus contact, gritty gloves, or frequent wiping when other requirements are equal. Approval should still use a common abrasion method and a visible acceptance limit—typically change in haze for a window, plus scratch, gloss, color, and legibility checks elsewhere.
When PET is not the best choice: do not default to PET when the part needs deep 3D forming, a gauge outside the selected PET family's range, or the lowest possible haze across a large gloss window. A hardcoated PC grade can also beat an uncoated or poorly matched PET construction on abrasion and chemical exposure.
5. Where Polycarbonate Wins
A polycarbonate overlay earns the first prototype when the geometry or optical window drives the design. The correct qualifier is “formable or optical PC grade,” not simply “PC.”
5.1 Named PC grades cover deeper forming routes and thicker gauges
Covestro lists Makrofol DE 1-4 as a gloss/very-fine-matte PC film offered from 75 to 750 µm and suitable for high-pressure forming and film-insert molding. The same Makrofol DE family page lists DE 1-1 gloss/gloss from 125 to 1,000 µm and DE 6-2 fine-velvet/very-fine-matte from 50 to 750 µm. MacDermid's paired ranges stop at 250 µm for Autoflex EB PET and extend to 480 µm for Autoflex PC.
SABIC's LEXAN 8B35E sheet gives another PC example: a velvet/very-fine-matte film in 0.125–0.500 mm manufacturing ranges, described for thermoforming, hydroforming, embossing, die cutting, and bending. These product ranges support PC when a prominent formed feature or thick fascia is required. They do not create a universal emboss-depth limit. Tool radius, hardcoat, ink deposit, gauge, forming temperature, and recovery still need coupon trials.
5.2 A clear gloss PC grade can produce the lowest haze
For a display window, total transmission alone is incomplete. The paired Autoflex PC and Autoflex EB PET gloss data report 92% ±2% transmission and less than 0.3% haze for PC, versus 91% ±2% and less than 2% haze for PET under ASTM D1003. That makes the named PC grade the better optical starting point for a wide, clear indoor window.
Finish can erase that advantage. The textured LEXAN 8B35E sheet reports 86% transmission and 100% haze on its default 0.250 mm sample. That film is intentionally diffusing, not defective. A window specification should therefore state film grade, gauge, surface, hardcoat, printed ink stack, display type, viewing angle, and acceptable haze/transmission after abrasion and cleaning.
5.3 PC can be selected for process fit, not an assumed price
The broad PC gauge and finish menus may reduce the need for a separate rigid lens or a secondary forming operation on some designs. That possibility belongs in a design review, not in a blanket cost claim. No current, like-for-like quotation set was available for this article, and substrate price alone omits hardcoat, printing, forming, die cutting, adhesive, scrap, inspection, and assembly yield.
When PC is not the best choice: do not default to PC for a highly cycled embossed key, an undefined disinfectant or solvent set, or a permanent outdoor installation using a standard indoor grade. In those cases, start with flex-qualified PET or a specifically weatherable/chemical-resistant construction, then compare finished coupons.
6. Outdoor, Chemical, and Hardcoat Exceptions
Outdoor exposure and chemical cleaning are grade problems before they are polymer problems. Weatherable PET and UV-protected PC both exist; hardcoated PC can pass demanding chemical contacts; textured PET can transmit plenty of light while remaining visually hazy.
| Named construction | Published condition | What the evidence supports | What it does not support |
|---|---|---|---|
| Tekra ProTek Weatherable Clear HS PET, 7/10 mil | SAE J2527 xenon arc: ΔYI 0.5 at 1,000 h and 1.1 at 2,000 h; <1% haze and 91% transmission | A clear, hardcoated, weatherable PET option exists | A field-year conversion or finished-overlay warranty |
| Covestro Makrofol SR906 PC, 175/250/375/500/635 µm | UV-protected acrylic functional layer; weathered YI 1.1 after 1,000 h to DIN ISO 4892; ≥89% transmission and ≤0.5% haze | A UV-protected, clear, formable PC option exists | Performance of standard unprotected PC or the bonded assembly |
| Tekra Marnot XL Matte PC, 7–30 mil | Post-UV-cure samples: listed 20% bleach passed 24 h at 23°C and 50°C; mustard stained after 24 h at 50°C | Hardcoated PC can resist some aggressive contacts, and results change with contaminant and temperature | A universal cleaner whitelist or performance of ink, edges and adhesive |
| MacDermid Autotex XE PET, Fine/Velvet | 92% ±2% transmission but 58% ±5% / 71% ±5% haze under ASTM D1003 | A textured weatherable PET can transmit light while diffusing it strongly | Suitability as a clear display window |
The PET and PC weathering values above cannot be ranked against each other: the suppliers used different standards and constructions. ASTM G154-23 also warns that fluorescent-UV apparatus operation does not, by itself, define a performance result. A report needs lamp type, irradiance, UV/wet cycle, temperatures, duration, controls, and the property measured before and after exposure. Chamber hours do not convert directly into years outdoors.
That boundary matters for marine and outdoor equipment. ASTM G154 does not reproduce saltwater, pollution, or biological attack. A marine qualification should add the actual salt or cleaning exposure, wet/dry cycling, edge and cutout inspection, adhesive peel or seal checks, and optical/graphic acceptance after exposure. If the project claims an IP code, test the enclosure according to the applicable IEC 60529 requirement rather than assigning the code to the film.
Hardcoat coverage has a physical limit. Tekra's hardcoated-versus-uncoated guidance notes that the coating protects the film surface, not exposed cut edges. Window edges, holes, emboss radii, ink boundaries, and adhesive interfaces therefore belong in the chemical coupon.
Flame behavior follows the same rule. Covestro's selector identifies particular flame-retardant PC grades and a stated UL 94 result at a stated gauge; that does not make generic PC—or a decorated, adhesive-backed overlay—flame-qualified. The exact film, color, thickness, print and assembly evidence must match the product requirement.
7. Decision Matrix — Which Construction Should You Specify?
Use the matrix to choose the first prototype, not to release production. Each row assumes the exact supplier grade and finished stack will be tested.
| Dominant requirement | Start with | Why | Reject or reconsider when… |
|---|---|---|---|
| High-cycle embossed membrane-switch keys | Flex-qualified hardcoated PET | Named PET overlay films publish supplier actuation screening | The PET grade lacks the required window, forming, weathering, or flame evidence |
| Deep 3D feature, HPF, FIM, or thick decorative fascia | Formable hardcoated PC | Named PC families cover these processes and broader thick gauges | The hardcoat/ink stack is not approved for the actual draw and radius |
| Large, clear indoor display window with little flex | Low-haze gloss PC | Paired supplier data give PC the lower haze | Cleaning, abrasion, polarization, glare, or impact tests fail |
| Repeated cleaning before the final cleaner list is frozen | Hardcoated PET as the conservative screen | Named PET grades publish strong conditioned chemical data | A qualified PC hardcoat passes the final cleaner matrix and better meets optical/forming needs |
| Stylus, gritty glove, or abrasive wipe contact | Either base with the better qualified hardcoat | Surface coating, cure and finish dominate the wear interface | Results use different wheels, loads, cycles, haze setups, or acceptance limits |
| Permanent outdoor clear window | Weatherable PET and UV-protected PC coupons | Both material families have grade-specific weatherable constructions | The report omits exposure cycle, color/haze endpoint, ink, adhesive, edges, or condensation |
| Outdoor textured keypad with frequent flex | Weatherable, flex-screened PET first | A named PET construction can combine texture, weathering intent, and supplier flex screening | The window or forming requirement cannot be met by that grade |
| Required flame classification | Exact documented grade, color, and thickness | Flame behavior is not a generic PET-versus-PC property | Evidence covers only base film, not the required component or assembly scope |
| Marine ingress requirement | Complete sealed HMI assembly | IEC 60529 applies to enclosure protection | The proposal assigns an IP code to film alone |
| Rigid, highly scratch-resistant window with no flex function | Consider a separate lens architecture | Separating lens and keypad functions may avoid a compromised single film | Added interfaces, sealing, thickness, weight, or assembly complexity are unacceptable |
For this polyester vs polycarbonate graphic overlay decision, PET is the default only when cyclic flex or an uncertain chemical set controls the risk. PC is the default only when the selected grade's forming or optical advantage controls the risk. If weathering, flame, ingress, or severe abrasion is the real requirement, the correct answer is neither generic polymer; it is a documented construction that passes the same project test.
8. Validation Matrix and Project Input Checklist
Material selection closes only after representative printed, formed, cut, and adhesive-backed samples pass a written test matrix. A supplier's quality and testing plan should preserve the film lot, ink/cure record, adhesive lot, drawing revision, conditioning, equipment settings, raw observations, and failure photographs.
Finished-stack test matrix
| Risk to close | Method baseline | Conditions that must be written down | Reportable output |
|---|---|---|---|
| Display haze and readability | ASTM D1003 | Grade, gauge, finish, hardcoat, printed window stack, conditioning, instrument/procedure, viewing orientation | Initial and post-exposure haze/transmission; visual defects |
| Surface abrasion | ASTM D1044 | Sample backing, wheel, load, cycles, wheel resurfacing, conditioning, hazemeter geometry | Δhaze in abraded track; scratch, gloss, color and legibility observations |
| Cleaner, disinfectant, oil, sunscreen, insect repellent, or salt contact | ASTM D543 wet patch/wipe or stressed exposure; ISO 2812-4 spot method where appropriate | Exact product, active chemistry, concentration, cloth/pad, volume, dwell, wipe count, temperature, applied strain, recovery | Swelling, staining, cracking, haze/color/gloss change, ink adhesion, edge lift, delamination |
| Sunlight, heat, and condensation | ASTM G154 fluorescent UV or a justified xenon-arc method | Lamp/filter, irradiance, UV/wet cycle, black-panel/chamber temperatures, duration, controls, replicates | Yellowness or color change, haze, gloss, cracking, embrittlement, ink and adhesive condition |
| Emboss and switch fatigue | ASTM F1578 assembly cycling | Film and spacer gauges, emboss/radius, actuator geometry/hardness, force or travel, rate, temperature, electrical load, target cycles | Electrical closure, tactile-force/displacement drift, film/ink/hardcoat cracking, key-shape change |
| Temperature and humidity | Project equipment profile plus supplier limits | High/low temperatures, dwell, ramps, humidity, powered/unpowered state, number of cycles | Dimensional shift, blocking, adhesion, optical change, cracking, tactile/electrical function |
| Edge seal and enclosure ingress | Applicable IEC 60529 assembly test | Complete housing, adhesive pattern, vents, cutouts, cable tail, assembly pressure and preconditioning | Enclosure pass/fail plus leak path and post-test function |
No table entry supplies a universal acceptance number. The OEM drawing must define pass/fail limits that correspond to display readability, graphic appearance, tactile behavior, sealing, and product safety.
Drawing and sample-approval checklist
Before approving a polycarbonate or polyester control panel overlay, supply:
- Exact film supplier, grade, gauge, finish, hardcoat, and print-side primer
- Artwork revision, color standard, opacity target, dead-front stack, and first-surface treatments
- Display type, window dimensions, viewing angle, polarization concerns, and initial haze/transmission limits
- Flat or embossed key geometry, radii, spacer opening, force/travel target, actuator shape, and expected cycles
- Every cleaner, disinfectant, lubricant, oil, sunscreen, insect repellent, and salt exposure by product name or SDS
- Concentration, application method, dwell, wipe material, wipe frequency, temperature, and whether the film is under strain
- Wear contacts: bare finger, glove material, stylus, grit, tool, or moving part
- Outdoor location, orientation, sunlight/condensation cycle, climate, saltwater exposure, and required service inspection
- Housing material, texture, curvature, surface treatment, venting, cutouts, tail exit, and edge distance
- Adhesive grade, coverage pattern, gasket or spacer, application pressure, assembly temperature, and cure/dwell
- Required material or product documentation, stated without assuming that a resin family satisfies it
- Prototype quantity, test sequence, failure definitions, retained control, and signed golden sample
The concrete next step is simple: share the cleaning, wear, and outdoor conditions before the film is nominated. Include the actual cleaner names and concentrations, wipe schedule, contact tool or glove, key-cycle target, display-window requirements, and outdoor or marine exposure. JASPER can review that input package as one possible graphic-overlay manufacturing option; the released material should still be the construction that passes the agreed test matrix.
9. Frequently Asked Questions
Is polyester or polycarbonate better for a graphic overlay?
Neither is universally better. Start with hardcoated PET when repeated flex or an uncertain aggressive-cleaner set dominates. Start with a qualified PC grade when deep forming, thick film, or a very low-haze gloss window dominates. Outdoor, flame, abrasion, and ingress requirements need grade- or assembly-specific evidence.
Which material lasts longer under repeated button presses?
A flex-qualified PET overlay is the stronger starting point. MacDermid Alpha publishes more than 5 million actuations for named hardcoated PET films under its internal method, while its cited Autoflex PC sheet states no switch-life value. Validate the printed, embossed, bonded switch under ASTM F1578 conditions before releasing a life claim.
Can a hardcoated polycarbonate overlay withstand disinfectants and solvents?
Yes, some hardcoated PC grades can. A valid answer needs the exact chemical, concentration, contact method, dwell, wipe count, temperature, applied strain, and failure criterion. A pass on an unprinted flat coupon does not automatically qualify ink, adhesive, cut edges, windows, or a stressed emboss.
Which material gives the clearest display window?
The named gloss PC grade wins the paired MacDermid Alpha comparison: it reports less than 0.3% haze, versus less than 2% for gloss PET, under ASTM D1003. That is not a universal resin rule. Texture, antiglare coating, gauge, printed layers, abrasion, and display polarization can change the finished window.
Can polycarbonate graphic overlays be used outdoors?
Yes, when the exact PC grade includes suitable UV protection and passes the project weathering test. Covestro Makrofol SR906 is one published acrylic-layer, UV-protected example. Standard indoor PC should not inherit that evidence, and accelerated chamber hours should not be translated directly into outdoor service years.
Does a hardcoat make PET and PC equivalent?
No. A hardcoat can improve surface scratch, abrasion, glare, and chemical behavior, but the base film still influences flex, forming, gauge availability, and stress response. The coating also does not protect every cut edge or automatically qualify second-surface ink and adhesive, so complete coupons remain necessary.
What thickness should a polyester control panel overlay use?
There is no universal thickness. One named hardcoated PET family spans 130, 180, and 250 µm; other textured families use different ranges. Select gauge with the supplier and converter after fixing key feel, emboss geometry, window optics, forming, print registration, housing support, and the required fatigue test.
What should an OEM send before graphic overlay material selection?
Send the film and drawing requirements, actual cleaner names and concentrations, wipe method and frequency, wear contacts, key geometry and cycle target, display-window limits, outdoor or marine exposure, housing surface, adhesive and seal geometry, required documentation, test sequence, failure definitions, and golden-sample approval criteria.
10. Methodology and Disclosure
This comparison used public supplier technical data and official standards pages available through 2026-07-25. A quantitative value was included only when the source identified a grade or product family, finish or gauge where relevant, and a test method or explicit supplier boundary. Ranking articles were used to assess search intent and content gaps, not as technical evidence. The existing same-topic page on the previous JASPER site was inspected as an incumbent only; its claims were not carried forward unless independently re-verified.
Supplier values are usually typical laboratory results, not purchase specifications. Different hardcoats and methods cannot be cross-ranked when conditions differ. Film availability and revisions can change, so the current TDS and the converter's material declaration should be checked when the drawing is released.
Disclosure: This comparison was commissioned for JASPER, a manufacturer of graphic overlays and other HMI components. JASPER is neither PET nor PC, but it has a commercial interest in overlay projects. Named supplier grades appear because their public documents support a decision boundary; inclusion is not an endorsement or a claim that JASPER currently stocks the grade. No customer-specific project, price, MOQ, lead time, or achieved test result is asserted.
Choose the film after the exposure list is real
Send the artwork, finished geometry, flexing, windows, forming depth, cleaners, UV exposure, housing, adhesive, and acceptance criteria. JASPER Engineering will compare the qualified PET and PC routes.