Foil on polyolefins fails for one reason far more often than any other: surface energy. Everything else — temperature, dwell, die material — is secondary to getting the part treated and stamped before that treatment decays.
Surface energy is the whole problem
Adhesives need to wet the surface to bond. Untreated PP sits around 29 mN/m and PE around 31 mN/m, below the ~38 mN/m threshold most foil adhesive systems require. Corona or flame treatment oxidises the surface and raises it above that threshold.
Treatment decays. Depending on the polymer, additives and storage conditions, a treated part can drop back below threshold within days. Treat as close to stamping as the line allows, and verify with dyne pens or ink at the stamping station rather than trusting the treatment record.
| Polymer | Surface energy | Treatment | Temperature |
|---|---|---|---|
| PP | ~29 mN/m | Required | 130–160 °C |
| PE / HDPE | ~31 mN/m | Required | 120–150 °C |
| PET / PETG | ~43 mN/m | Usually not | 120–140 °C |
| ABS | ~42 mN/m | Usually not | 130–160 °C |
| PC | ~46 mN/m | Not required | 130–160 °C |
| PVC | ~39 mN/m | Not required | 110–140 °C |
Testing adhesion the right way
- Wait 24 hours. Plastic-grade adhesives continue to build bond, and an off-press test both understates the final result and hides slow failures.
- Cross-hatch and tape pull is the standard check; add a thumbnail scratch for parts that will be handled.
- Test against the product that will be inside — creams, oils, solvents and fragrances attack the bond from the other side.
- Test the actual moulded part, not a plaque. Mould release agents on production tooling are a common invisible cause of failure.
Practical fixes when it still fails
If treated parts still fail, check for mould release migration (wipe with IPA and retest), verify the dyne level at the stamping head rather than at the treater, and raise temperature in 10 °C steps while watching for part distortion. If the geometry is curved, a silicone roller with matched hardness will contact the surface more evenly than a flat die.
MOQ and lead time by product
Minimum order quantity and production lead time for the products used in this industry. Each row links straight to the product page with full specifications.
| Product | MOQ | Lead time |
|---|---|---|
| Matte Silver Hot Stamping Foil | 50 kg | 15–20 days |
| Holographic Rainbow Foil | 50 kg | 15–20 days |
Frequently asked questions
Why does foil peel off polypropylene?
- Untreated polypropylene has a surface energy of about 29 mN/m, far below the roughly 38 mN/m an adhesive needs to wet the surface. Corona or flame treat the part immediately before stamping, use a plastic-grade foil, and verify with a dyne pen at the stamping station.
How long does corona treatment last?
- It decays over hours to days depending on the polymer, its additives and storage conditions. Always re-check the dyne level at the point of stamping rather than relying on when the part was treated.
Does PET need pretreatment before hot stamping?
- Usually not. PET and PETG sit around 43 mN/m, high enough for a plastic-grade foil to bond directly at 120–140 °C. ABS and polycarbonate behave similarly; only the polyolefins reliably need treatment.
What temperature should I use on plastic parts?
- 120–160 °C depending on the polymer, with short dwell to avoid distortion. Raise temperature in 10 °C steps and stop as soon as adhesion is achieved — excess heat marks the part far more visibly than it does paper.
How do I stamp a curved plastic container?
- Use a silicone roller die with a hardness matched to the curvature so contact pressure stays even across the image. A flat die on a curved surface transfers only along the tangent line and produces a fading image at the edges.