How-to · Nº 02
How to make labels stick to plastic
Labels peel off plastic because of surface energy, not bad glue: HDPE (~31 dyne/cm) and polypropylene (~29) sit below the ~36 a standard adhesive needs to wet and bond. The fix is either a low-surface-energy (LSE) high-tack adhesive, or raising the surface energy by corona/plasma treatment or a primer (to ~44–50 dyne/cm) — plus clean prep and firm pressure.
Some plastics simply will not hold an ordinary label, and the reason is surface energy. HDPE and polypropylene sit around 29–31 dyne per centimetre, below the roughly 36 an everyday adhesive needs to wet a surface, so the glue beads up instead of flowing out and the label lifts at the edges. The fix is a change of chemistry: an adhesive built for low-energy plastic, or a treatment that raises the surface energy enough for an ordinary one to bond.
You'll need
- ▪LSE high-tack adhesive (specified on the label)
- ▪70%+ isopropyl alcohol
Step by step
- 01
Identify the plastic
HDPE and polypropylene (PP) are low-surface-energy plastics — about 31 and 29 dyne/cm, below the ~36 threshold. This, not "bad glue", is why standard labels lift off them.
- 02
Specify an LSE adhesive
Ask for a low-surface-energy high-tack adhesive formulated for the resin — a generic permanent acrylic is not enough on its own. For short indoor runs a rubber adhesive also grips LSE plastic.
- 03
Or treat the surface
At volume, have the container corona- or plasma-treated, or use a primer, to raise the surface energy to ~44–50 dyne/cm so a normal adhesive can bond.
- 04
Clean and dry
Wipe with 70%+ isopropyl alcohol — twice for parts fresh from moulding — and let it flash off before applying.
- 05
Apply firm pressure and let it cure
Press the label down with firm, even pressure. The bond builds over roughly 24 hours, so give it time before stressing the label.
The surface-energy problem, in plain terms
Before an adhesive can bond, it has to wet the surface — flow into intimate contact with it. Whether it can is set by surface energy, measured in dyne/cm, and roughly 36 is the line an everyday adhesive has to clear. Glass (200–300) and metal (aluminium ~840) sit far above it, so a standard adhesive grips them instantly.
HDPE at around 31 dyne/cm and polypropylene at 29 fall below, and there the adhesive beads up instead of flowing out, like water on a freshly waxed car. The label touches the surface at only a fraction of its area, and lifts. That is why pressing harder does not help: you cannot force a mismatched adhesive to wet a surface it chemically repels.
Three fixes, in order of effort
The simplest fix is chemistry. A low-surface-energy (LSE) high-tack adhesive is formulated to bond the very plastics a standard acrylic cannot, and for most jobs it is the entire answer — you specify it on the label and move on.
If you are labelling at volume, raising the surface energy is more reliable still. Corona, flame or plasma treatment, or a primer, lifts a treated plastic to about 44–50 dyne/cm — above the threshold — so an ordinary adhesive can bond. Pressure and dwell time are refinements at the margin, worth doing once the adhesive is right and no substitute for getting it right.
Squeeze bottles and recycled resin
Two complications catch a job even when the adhesive is right. A squeezable bottle flexes in the hand, so a rigid face cracks or lifts at the seam; pair the LSE adhesive with a conformable film — clear BOPP or vinyl — that moves with the bottle.
And recycled or unknown plastic has unstable surface energy that drifts from batch to batch, often with mould-release residue on freshly moulded parts. Wipe twice with isopropyl alcohol to clear the release agent, and test each batch rather than trusting a single spec sheet — the resin that held last month can behave differently this month.
Good to know
- →For a squeezable bottle, use a conformable film (clear BOPP or vinyl) so the label flexes without lifting.
- →Recycled or unknown plastics have unstable surface energy — test per batch.
- →See the surface energy (dyne) table for where each plastic sits.
Common questions
Why do labels peel off HDPE and polypropylene?
Their surface energy (~31 and ~29 dyne/cm) is below the ~36 a standard adhesive needs to wet and bond, so the label never fully adheres and lifts at the edges. Use a low-surface-energy high-tack adhesive or corona-treat the surface.
What adhesive sticks to plastic bottles?
A low-surface-energy (LSE) high-tack adhesive for HDPE/PP; a standard permanent acrylic is fine on higher-energy plastics like PET and PVC. Match the adhesive to the specific resin.
Not sure it'll hold?
Tell us your surface and job and we’ll spec the right material and adhesive — and ship a free sample to test.