Stickers on Rough Surfaces: What High-Tack Adhesives Can and Can't Do

On Monday the company logo goes on the plastic transport box. By Friday one corner is sticking up, and you can lift half the sticker with a fingernail.

Stickers on rough surfaces and on some plastics have a hard time. Usually the reason is an adhesive that doesn't suit the surface. Adhesive tape also holds differently on a non-stick frying pan than on cardboard.

A high-tack adhesive helps on many difficult surfaces, but not on all of them. This article is based on data sheets and processing guidelines from several vinyl and adhesive manufacturers. Whatever the data sheet for your vinyl says comes before this text.

Why stickers stick poorly to rough surfaces

Too little contact. Adhesive only holds where it touches the surface. On a rough or textured surface it sits on the peaks and barely reaches the valleys. A comparison you can feel: according to one vinyl manufacturer, if a surface is rougher than 150-grit sandpaper, the adhesive finds it much harder to make full contact. A sheet of it held next to the part is the first thumb test.

The adhesive doesn't wet the surface. Every surface has a surface energy. Glass and aluminium are high and easy to apply stickers to. Polyethylene (PE) and polypropylene (PP) are low, and so are many powder coatings. A normal adhesive spreads poorly there, rather like water on a freshly waxed bonnet.

What a high-tack adhesive does differently

"Tack" is the initial stickiness: how quickly an adhesive grabs on light contact. A high-tack adhesive grabs with only light pressure. On difficult surfaces that is exactly what you want. During application it is a nuisance: once the sticker is down, you can't slide it any more.

Standard acrylic adhesives usually hold poorly on PE and PP. Rubber-based adhesives hold there, but generally cope less well with heat, weather and chemicals. Special high-performance acrylics combine high initial tack with a lasting bond. One branded polymeric vinyl with a high-tack acrylic adhesive is expressly designed for PE and PP. A second manufacturer also approves its high-tack vinyl for powder-coated surfaces.

The peel adhesion, meaning the force needed to pull the sticker off, shows how strong such an adhesive is. The data sheet for the polymeric vinyl gives an initial value of 520 N/m on PE and a final value of 600 N/m, measured in the lab using the FINAT FTM-1 test method.

On the actual part, full adhesion takes time. Another vinyl manufacturer allows about three days. For the first 24 hours the surface should not drop below the application temperature.

The downside: high-tack adhesives are permanent adhesives. The data sheets do not promise that they come off without leaving residue. Our standard sticker also uses a permanent adhesive. It is still not a high-tack adhesive. If a sticker has to hold permanently on a difficult surface, ask us about the right adhesive before you order.

Which surfaces strong-adhesive stickers are made for

The data sheets of high-tack vinyls list smooth, flat or only slightly curved surfaces as the area of use. So high-tack is mainly intended for difficult materials. Coarse textures remain tricky even with it.

Unprinted and applied vertically, high-tack data sheets give five to seven years of outdoor durability in a Central European climate. South-facing positions and industrial air shorten that. For printed stickers these values don't apply automatically, as the ink and laminate also play a part. We'll tell you the durability for the specific material when you enquire. A protective laminate keeps UV light and abrasion away from the print. More on indoor and outdoor use: Stickers Must Meet Specific Requirements.

Powder-coated metal

Powder coating may need a special adhesive. Powder coatings can contain waxes that weaken adhesion. So a test application comes before installation.

Only apply stickers to freshly coated or painted parts once they have fully cured. We allow three weeks from coating for this, for powder coating just as for wet paint – that is also what the vinyl manufacturer requires. Dry to the touch does not mean fully cured.

Low-surface-energy plastics

On PP a special adhesive is often enough. Some plastics also need an adhesion promoter. For PE, even flame, corona or plasma treatment by a specialist company may be an option.

Then there is the surface itself. One vinyl manufacturer only approves unpainted plastic parts if they are completely smooth. On textured plastic, adhesion can be considerably lower. If both come together, it gets tight.

Test the surface before you order

Water drops. Put a few drops of water on the clean surface. If they bead up, a normal vinyl will stick poorly there, and you'll need a special adhesive and a test. If the water spreads into a continuous film, that points to a surface that is easy to apply stickers to. The test does not show roughness or curing.

Test pen. A test pen for surface tension, often called test ink, measures more precisely. Manufacturers do not give a fixed threshold value for it.

Test application. Apply a piece of the intended vinyl to the original part and, for comparison, a second piece to glass. Peeling after 24 hours gives a first indication; the test is more reliable after about three days. If the piece on the part holds noticeably less well or small bubbles form: clean more thoroughly and test again. Professionals measure the peel force and compare it with the minimum value in the data sheet. If it is still not enough after cleaning again, you need a vinyl with stronger adhesion. Before ordering, you usually don't have the vinyl to test with. So mention the test when you enquire.

Preparation and adhesion promoter (primer)

Powder coating is cleaned in three steps: first with cleaner and water, then with a solvent cleaner against grease and oil, and finally with isopropanol. Wipe dry each time before the liquid evaporates. Always try any solvent cleaner on an inconspicuous spot first: does it attack the paint or the plastic? Isopropanol is highly flammable. Ventilate the room and work without naked flames.

Glass cleaners with ammonia or silicone, washing-up liquids with care additives and cleaners with nano-sealing stay in the cupboard. Their residues weaken adhesion.

Adhesion promoter. It slightly dissolves the plastic surface and anchors itself in it. Solvent-based adhesion promoters improve adhesion on PE, PP, ABS, metal and paint, for example. They are applied thinly and sparingly with a brush or dauber to the cleaned, dry surface and should flash off for about five minutes before the vinyl goes on. Excess material only comes off with a harsh solvent. So check first on a hidden spot whether the paint or plastic can take it. Adhesion promoters are highly flammable. The test shows whether the extra step is worth it.

These notes are general. What counts are the data sheets and safety data sheets of the products used, which also state the protective equipment you need. If in doubt, our sign-making team will take care of the installation.

During application high-tack is unforgiving. On rough or textured surfaces, apply dry. A hard squeegee puts more pressure on the surface, a soft one follows contours better. On textured surfaces, press the vinyl into the texture with a short, stiff application brush and then go over all edges firmly a second time, otherwise they lift. According to one manufacturer, vinyl sticks best at a surface temperature of about 21 to 23 °C. Depending on the high-tack vinyl, the minimum temperature is 4 °C or 10 °C; the data sheet is what counts.

Where even high-tack gives up

Silicone and wax in the paint or on the surface are the typical adhesion killers. Manufacturers only promise good adhesion on surfaces free of grease, wax and silicone. PTFE-coated parts and silicone have an even lower surface energy than PE and PP. The high-tack data sheets we consulted do not list any approval for them. Without a test, we wouldn't promise anything there.

Textures rougher than 150 grit remain difficult. If the test doesn't hold, there are two ways out: find a smooth, painted area on the part, or use a sign that is fixed mechanically.

Textured polypropylene boxes: where does the logo go?

Take a typical case: a trade business wants to mark its transport boxes with the company logo. The boxes are made of polypropylene with textured side walls; only a narrow smooth strip runs along the top edge. A normal sticker in the middle of the texture soon lifts at the corners.

First comes the water drop test. Then one test strip with high-tack adhesive on the texture and one on the smooth edge of an original box, plus a comparison piece on glass. They are peeled after 24 hours and again after about three days.

If the strip on the texture holds, a logo is possible there. It is, however, outside the manufacturer's approval, and there is no durability guarantee for it. The smooth edge is safer. If only the strip on the edge holds, a smaller logo goes there. If neither holds, a sign is the answer.

Better one test strip too many

From our founder's more than 30 years in the trade, and from our own business since 2017, one inconvenient sentence remains: the strongest adhesive is no substitute for a test strip.

High-tack copes with difficult surfaces. On an unknown surface it is still an experiment. Wax in the paint or a texture you only see in raking light is not written on any delivery note. If you apply a piece to the original part before the series, you may save yourself a second print run. For us, the question about the material therefore comes before the question about the design.

More on the surface as a factor for success: Stickers You Can't Overlook. Vinyls for special requirements can be found under Foil Technology.

Conclusion: test before the series

For PE, PP and powder coating there are high-tack vinyls with manufacturer approval. Whether they hold on your part is decided by the test, not by a label saying "strong adhesion". Before you order, clarify:

• Material and surface: powder coating or plastic, smooth or textured? Does water bead up?
• Use: indoors or outdoors, and how long should the sticker last?
• Installation: who will apply it, and is a test on the original part possible before the series?

Don't want to apply it yourself? Then our sign-making team will take care of the installation. Tell us via our contact page what the part is made of and what the surface feels like. We'll give you no-obligation advice. Custom stickers can be ordered online at koeck-print.at. If one needs to hold permanently on powder coating or plastic, ask us first.

Frequently asked questions

Does a high-tack sticker hold on any plastic?

No. According to the data sheets, high-tack vinyls are designed for hard-to-bond plastics such as PE and PP, and even there for smooth, flat or slightly curved surfaces. On textured plastic, adhesion can be considerably lower, and silicone on the surface weakens it further. Before the series, test a piece on the original part, after 24 hours and after about three days.

Can a strong-adhesive sticker be removed again?

High-tack adhesives are permanent adhesives. The data sheets do not promise removal without residue. So expect that residue may remain. If the marking is meant to come off later, mention it before you order. Then we can weigh up whether a removable adhesive is enough on that surface.

How can I tell whether my surface is difficult to apply stickers to?

Put a few drops of water on the clean surface. If they bead up, a normal vinyl will stick poorly there, and you'll need a special adhesive and a test. A test pen for surface tension measures more precisely. If the surface is rougher than 150-grit sandpaper, contact becomes difficult. Only a test application on the original part gives you certainty.