Why surface energy decides whether tape sticks
A pressure-sensitive adhesive only bonds where it can flow out and wet the surface. That works when the surface energy of the part is higher than that of the adhesive. Metals and glass sit in the hundreds of dyn/cm and are easy; polypropylene and polyethylene sit near 30 dyn/cm, below most standard acrylic adhesives, so the tape beads up on a microscopic scale and peels off.
Surface energy is given in dyn/cm, mN/m or mJ/m²; the three numbers are the same. 3M groups surfaces as high (metals, glass: hundreds to thousands), medium (most engineering plastics and paints: from about 36 dyn/cm) and low (polyolefins and non-stick surfaces: below 36 dyn/cm). tesa draws the line at 36–38 mN/m, which is why this chart marks that band as borderline.
Surface energy of common materials
Values are from two published tables: the surface energy chart in 3M's Bonding Solutions catalogue and Accu Dyne Test's critical surface tension table. Where both list a material, the range spans the two. Treat them as typical values: the grade, fillers, mould release and plasticizers in your part can move the real number.
| Material | dyn/cm | Class |
|---|---|---|
| PTFE (Teflon) | 18–19.4 | Very low |
| Silicone rubber | 20.1 | Very low |
| PVF film (Tedlar) | 28 | LSE |
| Polypropylene (PP) | 29–30.5 | LSE |
| Polyethylene (PE, HDPE, LDPE) | 31–31.6 | LSE |
| TPO / olefin elastomers | Varies | LSE |
| EVA | 33 | LSE |
| Powder coating | Varies | LSE |
| Polystyrene (PS) | 34–36 | Borderline |
| Acetal (POM) | 36–37 | Borderline |
| Acrylic (PMMA) | 37.5–38 | Borderline |
| Modified PPE (Noryl) | 38 | MSE |
| PVC, rigid | 37.9–39 | MSE |
| ABS | 38.5–42 | MSE |
| Polycarbonate (PC) | 42–44 | MSE |
| Polyester (PET) | 39–43 | MSE |
| Polyurethane | 43 | MSE |
| Nylon (PA 6, PA 66) | 42.2–46 | MSE |
| Phenolic | 47 | MSE |
| Polyurethane paint (Polane) | 38 | MSE |
| Epoxy paint | 43–44.5 | MSE |
| Alkyd enamel | 45 | MSE |
| Tin | 526 | HSE |
| Zinc (galvanized steel) | 753 | HSE |
| Aluminum | 840 | HSE |
| Copper | 1103 | HSE |
| Stainless steel | 700–1100 | HSE |
| Glass and porcelain | 250–500 | HSE |
Which adhesive for which surface energy
- High and medium surface energy (metals, glass, ABS, PC, PET, nylon, most paints): standard acrylic adhesive. Acrylics resist heat, UV and chemicals and age well, so they are the default for most die-cut parts.
- Borderline, about 34–38 dyn/cm (polystyrene, acetal, acrylic sheet): test a standard acrylic and an LSE acrylic side by side on real parts.
- Low surface energy, below 36 dyn/cm (PP, PE, TPO, EVA, many powder coatings): LSE (modified) acrylic, such as 3M Adhesive 300LSE types and VHB LSE foam tapes, or a synthetic rubber adhesive. Rubber grabs fast but gives up heat, UV and solvent resistance.
- Very low, about 18–21 dyn/cm (PTFE, silicone rubber): silicone pressure-sensitive adhesive, or chemically etched PTFE film if an acrylic must be used.
Raising surface energy instead of changing the adhesive
When a standard acrylic is required — for temperature, approvals or cost — the surface can be treated instead. Production lines use flame, corona or plasma treatment on polyolefin parts and films; for lower volumes, an adhesion promoter (primer) wiped on before the tape does the same job.
Treatment fades over time on some plastics, so bond within the window the treatment supplier gives, and check the surface before bonding.
- Clean first: mould release, slip agents and oils lower the effective surface energy of any material.
- Measure: dyne test pens or inks (ASTM D2578 wetting tension) show whether a surface is above or below a target such as 38 dyn/cm in seconds.
- Then test: peel on the actual part, after the dwell time and conditioning the part will see.
Why surface energy charts disagree
Published values for the same plastic can differ by 5 dyn/cm or more. Some tables give critical surface tension (Zisman method), others total surface free energy from contact angles, and every table measured particular grades. Use a chart to see which class a material is in, not to split hairs between 40 and 42.
Frequently asked questions
What is the surface energy of polypropylene?
About 29–31 dyn/cm (mN/m): 29 in 3M's chart and 30.5 in Accu Dyne Test's critical surface tension table. That makes polypropylene a low surface energy (LSE) plastic, so standard acrylic tapes bond poorly unless the surface is treated.
Which double-sided tape sticks to polyethylene or polypropylene?
Tapes with an LSE (modified) acrylic adhesive, such as 3M 300LSE-type tapes and VHB LSE foam tapes, or synthetic rubber tapes for indoor parts. Alternatively, flame, corona or plasma treatment or a primer raises the plastic's surface energy so a standard acrylic tape will bond.
Is powder coating a low surface energy surface?
Often, but not always. Powder coatings vary widely with formulation; tesa groups them with the low energy surfaces and 3M lists them as a broad range. Check a sample with dyne pens and peel-test the tape before release.
What surface energy do you need for tape to bond well?
As a rule of thumb, standard acrylic adhesives bond reliably above about 38 dyn/cm. Between 36 and 38 dyn/cm results depend on the material and cleanliness; below 36 dyn/cm choose an LSE adhesive or treat the surface.
Can any tape bond to PTFE (Teflon) or silicone rubber?
Silicone pressure-sensitive adhesives can, because they wet very low energy surfaces. For acrylic adhesives, PTFE has to be chemically etched first. Peel values will still be lower than on metal, so test the bond on real parts.
Sources
- 3M — Categorizing Surface Energy (Science of Adhesion): surface energy classes
- 3M — Bonding Solutions catalogue: surface energy chart
- Accu Dyne Test — critical surface tension of polymers
- tesa — LSE converter assortment: low/high energy boundary at 36–38 mN/m
- Saint-Gobain Tape Solutions — acrylic, rubber or silicone adhesive
Bonding to a hard plastic?
ALS Tape converts LSE acrylic, silicone and acrylic tapes from 3M, tesa, Nitto and other brands into custom die-cut parts. Send a drawing with the two materials being bonded for a quote.
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