Surface tension — measured in dynes per centimeter (dyn/cm, numerically equivalent to mN/m) — is the property that determines whether an adhesive, ink, or laminating resin spreads and bonds across a film's surface, or beads up and fails; on a metallized PET web, it is the single most predictable variable behind delamination and adhesion complaints in converting.
Search this topic and most results are corona treater manufacturers or dyne-pen vendors explaining their equipment. Useful, but it doesn't answer what a converting engineer needs before switching film suppliers: can this roll go onto my laminator without a surprise? This guide gives you the surface tension, adhesion, friction, and heat-shrinkage numbers Expansteel films ship at — not marketing language — plus the handling practices that keep those numbers intact, and the documented industry causes behind the lamination failures converters run into most often.
A film bonds only when its surface energy is higher than the surface tension of whatever is being applied to it — fall short, and the adhesive beads instead of wetting out, leaving microscopic gaps that surface later as delamination.
This is basic wetting physics, not a metallized-film-specific rule: a material is wetted only if its surface energy is higher than the surface energy of the liquid applied to it (Vetaphone, Understand Corona Treatment). Industry rules of thumb translate that into practical dyne targets: solvent-based inks generally need 36–40 dyn/cm, water-based systems typically need 40–44 dyn/cm, and laminating or coating applications often call for 50 dyn/cm or higher (Diversified Enterprises, ACCU DYNE TEST). Fall below those thresholds and you have a wetting problem waiting to surface as a bond-strength problem.
Metallized PET adds a wrinkle: there are two chemically different surfaces on one roll. The aluminum face bonds through oxidation-based surface chemistry to the vapor-deposited metal layer, while the reverse, non-metallized PET face bonds through standard polymer surface treatment (Enercon Industries, Metallized Film Adhesion). The two faces do not behave identically and should never be assumed to share one dyne reading — which is why a usable TDS reports them separately, as ours does below.
Every roll leaves our five production lines already at print- and lamination-ready surface energy — these are measured TDS numbers, not target ranges.
All grades below are supplied at 12μm standard thickness, in roll widths up to 2400mm.
| Property | Unit | ES-VM / VM Plus | ES-GF | ES-GF01 | ES-C01 |
|---|---|---|---|---|---|
| Surface tension — aluminum face | mN/m | ≥48 (typ. 54) | — | — | — |
| Surface tension — non-aluminum face | mN/m | ≥44 (typ. 46) | — | — | — |
| Peel / bond adhesion strength | N/15mm | — | ≥2.2 | ≥3.0 | ≥4.0 (chemical coating) |
| Coefficient of friction — aluminum face | COF | ≤0.55 | — | — | — |
| Coefficient of friction — non-aluminum face | COF | ≤0.65 | — | — | — |
| Heat shrinkage, MD/TD (150°C, 30 min) | % | ≤3.0 | — | — | — |
| Standard thickness | μm | 12 | 12 | 12 | 12 |
Surface tension, COF, and heat-shrinkage figures are from the ES-VM TDS. ES-GF, ES-GF01, and ES-C01 share the same metallizing platform with additional adhesion-enhancing treatment or coating; confirm values not listed here against each grade's own TDS.
Metallized PET ships shelf-ready, but like any corona-treated web, its usable surface performance depends on how the roll is stored and handled before it reaches your laminator.
General converting-industry guidance commonly cites a storage range of roughly 60–80°F (16–27°C) and 40–60% relative humidity, out of direct sunlight and away from heat sources (Nobelus University; RTG Films). Keep rolls in original wrap until ready to run, re-wrap partial rolls before they sit idle, avoid stacking weight or impact that can telescope or crush the core, and give cold-stored rolls roughly 24–48 hours to acclimate before unwrapping.
Surface contamination is a separate risk from surface tension: dust, oils, fingerprints, or additive bloom can physically block adhesive contact even when a dyne reading is in spec, so keep rolls wrapped and away from contaminant sources until immediately before lamination (Enercon Industries, Metallized Film Adhesion).
Like all corona-treated films, treatment is not permanent: dyne level declines gradually with storage time, heat, humidity, and additive migration to the surface (Vetaphone, Understand Corona Treatment). We don't publish a decay curve, because the rate depends on your storage and handling as much as the film itself — the practical response is standard FIFO rotation, plus a quick dyne check before a critical run on any roll held in inventory for an extended period.
Most delamination and adhesion complaints trace back to a short list of well-documented causes — worth ruling out in order before treating a roll as defective.
Surface tension tells you bonding is possible — temperature, nip pressure, and line speed tell you whether it's reliable at your throughput, and that part depends on your adhesive system and your line, not on the film alone.
We intentionally don't publish a universal temperature, pressure, or speed table, because a number that works on one converter's line can under-bond or over-bond on another depending on adhesive chemistry (solvent, solventless, or water-based), coating weight, nip configuration, and target speed. The reliable starting point is your adhesive supplier's recommended processing range, validated with a peel or bond test on your own equipment — using our surface tension and adhesion baselines above to confirm the film itself is not the variable in question.
Want application-specific processing recommendations, or samples of the high-adhesion ES-GF series for your own trial? Contact our engineering team directly.
Decay depends on more than the film — storage temperature, humidity, and handling between the mill and your laminator all affect the rate, and these vary in the field. We ship at a verified surface tension (aluminum face ≥48 mN/m, non-aluminum face ≥44 mN/m) and recommend standard practice instead: rotate stock FIFO and re-check surface tension shortly before a critical run.
Both sides ship treated within our published minimums, but the aluminum face runs higher (≥48 mN/m, typically 54) than the non-aluminum face (≥44 mN/m, typically 46). Confirm which face your adhesive system specifies before running — don't assume the two sides behave identically.
Not necessarily — our films ship print- and lamination-ready. But standard practice for any corona-treated web is to "bump treat" again close to the point of lamination when a job falls outside a tight window, since treatment level is not permanent on any supplier's film. If your line already runs inline treatment, keep doing so.
We don't publish these, because they depend on your adhesive system, coating weight, nip setup, and target speed — not on the film alone. Start from your adhesive supplier's recommended range, validate with a peel test on your own line, and contact our engineering team for application-specific recommendations.
Keep rolls in original packaging, out of direct sunlight and heat, in a stable environment — general converting guidance commonly cites roughly 16–27°C (60–80°F) and 40–60% relative humidity. Let cold-stored rolls acclimate before unwrapping. We don't publish a specific shelf-life day count, since usable life depends on your actual storage conditions, not a fixed calendar date.
Confirm you tested the correct face (aluminum and non-aluminum have different minimums), confirm your dyne test method and roll location follow standard practice, and check whether extended inventory time allowed treatment decay or additive migration to lower the reading. If all three check out, contact our engineering team with your roll lot number.
Data source: Expansteel TDS measurements, updated 2026-07.
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