The core difference in one sentence: VMPET (ES-H) blocks oxygen and moisture with a vacuum-deposited layer of metallic aluminum and is fully opaque, while transparent AlOx (ES-T) blocks the same gases with a nanometer-thin layer of aluminum oxide — a ceramic, non-metallic coating — and stays optically clear.
Both are barrier technologies applied to the same 12 μm PET base film. The chemistry, not the base film, is what separates them: one deposits reduced aluminum metal, the other reacts aluminum with oxygen during deposition so the resulting film is a see-through oxide rather than an opaque metal. Expansteel runs both product lines — ES-H (VMPET) and ES-T (AlOx) — on the same facility, which means the numbers below are directly comparable rather than pulled from two different mills' datasheets.
Comparing the highest-barrier grade from each line shows exactly what you trade away — and gain — by going transparent.
| Item | Unit | ES-H03 (VMPET) | ES-T03 (Transparent AlOx) |
|---|---|---|---|
| Barrier layer | — | Metallic aluminum (vacuum metallized) | Aluminum-oxide (AlOx) ceramic coating |
| OTR | cc/m²·24h | ≤ 0.1 | ≤ 0.5 |
| WVTR | g/m²·24h | ≤ 0.3 | ≤ 0.5 |
| Light transmittance | % | Opaque · full light-block | ≥ 88 |
| Coating measure | — | Al optical density ≥ 2.5 O.D. | AlOx adhesion ≥ 5.0 N/15mm |
| Metal-detector line | — | Not TDS-validated* | Pass (validated) |
| Microwave reheat | — | Not TDS-validated* | Yes |
| Retort 121°C | — | Not TDS-specified | Yes |
| Base thickness | μm | 12 | 12 |
| Structure | — | Al-coated PET, mono-barrier | 3-layer: PET base + AlOx + protective top coat |
| Compliance | — | — | FDA / EU / REACH / RoHS |
*Metallic aluminum layers are widely reported across the packaging industry to generate strong non-ferrous signals on metal detectors and to arc under microwave energy — this is a general characteristic of aluminum-metallized/foil structures, not a specific pass/fail test result published on the ES-H datasheet. See the sourced explanation below.
| Grade | OTR (cc/m²·24h) | WVTR (g/m²·24h) |
|---|---|---|
| ES-H | ≤ 1.0 | ≤ 1 |
| ES-H01 | ≤ 0.5 | ≤ 0.8 |
| ES-H03 | ≤ 0.1 | ≤ 0.3 |
| ES-T | ≤ 2.0 | ≤ 2.0 |
| ES-T01 | ≤ 0.5 | ≤ 1.0 |
| ES-T03 | ≤ 0.5 | ≤ 0.5 |
Quick reference across all six standard grades. Every VMPET grade (H / H01 / H03) is fully opaque; every AlOx grade (T / T01 / T03) is ≥ 88% transparent.
Both technologies are applied by vacuum deposition, but what lands on the film is chemically different — and that difference is why one is see-through and the other isn't.
In VMPET production, aluminum is evaporated in a vacuum chamber and condenses directly onto the PET web as a continuous metal layer — the same reflective, opaque aluminum you'd see in foil, just far thinner. In AlOx production, aluminum atoms are ejected in the presence of oxygen gas and react in flight to form aluminum oxide (Al₂O₃) before landing on the film, building a thin ceramic-like layer instead of a metal one. Because the aluminum has already reacted with oxygen, the resulting coating is optically transparent rather than reflective, while still forming the continuous, gas-blocking layer that gives it barrier performance in the same class as metallization.
These aren't arbitrary limitations — they follow directly from having a continuous metal layer in the pack.
On a metal-detection line, an aluminum foil or metallized layer generates eddy currents and a large non-ferrous signal that can mask or mimic the much smaller signature of an actual contaminant, forcing lines to either desensitize the detector (risking missed contaminants) or accept more false rejects — a well-documented challenge in food metal-detection engineering. In a microwave, metal reflects and concentrates electromagnetic energy; thin or sharp-edged metal — exactly the geometry of a metallized film — is prone to arcing and sparking, which is why laminates containing foil or metallized substrates are not considered microwave-safe. AlOx sidesteps both problems by design: because the coating is a non-metallic oxide rather than reduced aluminum metal, it does not present the same conductive signal to a detector and does not arc under microwave energy — which is why ES-T is validated to pass metal-detector lines and is microwaveable, while VMPET structures generally are not used in either context.
The choice isn't "better" vs. "worse" — it's which constraint matters more for your product and your production line.
Product visibility drives purchase decisions (fresh pasta, deli items, bakery goods); your line runs in-pack metal detection and the pack itself must not trigger it; the pack needs to be microwaved by the end consumer; you need clear-window retort at 121°C; or you're moving toward mono-material, lower-foil structures for recyclability.
Contents are light-sensitive and need full UV/light blackout, not just gas barrier; you need the absolute lowest OTR/WVTR ceiling the line can reach (ES-H03 still measures tighter than ES-T03 on both); or cost per square meter is the primary constraint — vacuum metallization is a mature, high-throughput process and is generally priced well below ceramic/AlOx coating across the industry.
At the flagship tier, they sit in the same ultra-high-barrier class: ES-T03 measures OTR ≤ 0.5 cc/m²·24h and WVTR ≤ 0.5 g/m²·24h, while ES-H03 measures OTR ≤ 0.1 and WVTR ≤ 0.3. VMPET still reaches a lower absolute ceiling, but the gap is a matter of degree, not category — both are far above standard uncoated PET.
Expansteel does not publish ES-H as metal-detector validated. Aluminum-metallized layers are broadly known in the packaging industry to interfere with detector sensitivity by generating a strong background signal. If your line requires metal-detector compatibility, ES-T is the validated option.
Because it contains a continuous metallic aluminum layer. Metal reflects microwave energy and concentrates electrical current at thin or sharp points, which can arc — a known risk with foil- and metallized-film-based packaging generally. ES-T's AlOx coating is non-metallic and does not carry this risk, which is why it's validated as microwaveable.
Not on the gas-barrier side — ES-T03's OTR/WVTR are close to ES-H03's. But if your product's shelf life depends mainly on blocking light (UV-driven oxidation, flavor loss, vitamin degradation) rather than oxygen or moisture, VMPET's full opacity is still the stronger protection, since a transparent film by definition lets light through.
Across the industry, vacuum-metallized film is generally priced well below ceramic/AlOx-coated film, reflecting metallization's higher throughput and lower process complexity. Exact figures depend on order volume and structure — request a quote for both ES-H and ES-T to compare landed cost for your specific spec.
Yes. Both lines run on the same 12 μm PET base at Expansteel's facility, so a side-by-side trial isolates the barrier-layer variable rather than comparing two mills' different base films — most converters can only get one technology from a single supplier.
Data source: Expansteel TDS measurements, updated 2026-07.
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