Adhesive?

A pressure-sensitive adhesive (PSA) is the thin layer of polymer sandwiched between a face stock and a release liner. It is what makes a sticker stick. It seems simple. It is not.

A PSA needs to flow into the microscopic crevices of the substrate (initial tack), then build adhesion over the next minutes and hours (peel strength), then resist environmental challenge for the lifetime of the label (durability). The choice of adhesive is responsible for more “why does my label peel off?” conversations than the choice of face stock.

Acrylic. The default. Transparent when cured, UV-stable, weatherable, the broadest service temperature window. Most modern label stock uses acrylic adhesive unless there is a specific reason to use something else.

Rubber. Higher initial tack, cheaper, but yellows under UV and softens at warm temperatures. Used in short-life shipping labels, masking tape, and rubber-band-grade attachments where look and longevity do not matter.

Silicone. The specialist. Adheres to silicone substrates (medical, electronics) where acrylic cannot. Maintains stability at extreme temperatures. Roughly 5–8× the cost of acrylic.

Hot-melt. Cheap, fast to apply, excellent for cardboard packaging. Brittle below 0 °C, softens above 50 °C. The standard for shipping cartons.

Permanent. Bonds within 24 hours, builds to maximum adhesion, leaves residue if removed. Use for product labels meant to stay.

Removable. Lower initial bond, designed to peel cleanly within 6–12 months. Use for promotional packaging, returnable assets, surface protection.

High-tack. Aggressive grab on rough or low-energy surfaces (HDPE bottles, textured cardboard). The default for shipping cartons and corrugated packaging.

Repositionable. Very low adhesion; designed to be repositioned without curling. Use for short-life signage, photo-mounting, prototyping.

“Low surface energy” substrates — HDPE, polypropylene, untreated polyolefins — resist standard acrylics. Specify high-tack acrylic or corona-treated film if the target is a polyethylene bottle.

Cold-temperature application — most PSAs lose 50% of their initial tack below 5 °C. Either heat the substrate or specify a cold-temperature adhesive.

Plasticiser migration — flexible PVC bottles can leach plasticisers that attack the adhesive over months. Specify a plasticiser-resistant acrylic.

Wet surfaces — condensation, oil films, mould-release compounds all sabotage adhesion. The adhesive cannot wet the substrate if the substrate is already wet with something else.