How are airport luggage tags sticky without being sticky?

Submitted by That_Comic_Who_Quit t3_114is7q in askscience

Airport luggage tags are sticky without being sticky - but how?

I go to the self-service airport check-in and I weigh my suitcase and print off a luggage tag. It's a 2 inch wide and 2 foot long strip with printed information and then at both ends red circles. These circles show how I should wrap it around my suitcase handle and the two circles should meet so it can stick together.

Every time I think to myself "this will never work, it's not even sticky on the underside" but with airport witchcraft I take it around the handle make the two circles meet and it sticks like a sticky sticker. It's a pretty tight bond too. I have to yank it off the other end.

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sf_d t1_j94fib6 wrote

Airport luggage tags use pressure-sensitive adhesives, which stick to the luggage when pressure is applied but do not require any moisture or heat to become sticky.

The adhesive used on luggage tags is a type of acrylic adhesive that is applied to the back of the tag in a thin layer. When the tag is applied to the luggage, pressure is applied to the adhesive layer, causing it to flow into the surface of the luggage and create a bond.

These adhesives are designed to be strong enough to keep the tag in place during transit but can also be easily removed by the baggage handlers or the owner of the luggage. This is why you can easily peel off the luggage tag without leaving any residue on your luggage.

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That_Comic_Who_Quit OP t1_j94yrq0 wrote

Firstly, thank you for not deleting your comment.

Secondly, that's really interesting. My monkey brain thinks if it has moisture it can stick but you mentioned this is pressure sensitive (as opposed to moistureor heat)... what's the science behind a pressure sensitive adhesive?

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Indemnity4 t1_j98hp0j wrote

Pressure sensitive adhesive.

The glue material is "tacky" - that's a science word in this context.

Imagine an elastic band, maybe holding up your underwear. You can pull it to deform the shape, but it wants to snap back to the original shape.

The glues have lots of little hairs, sub-microscopic in size. When you push/pull them, the hairs move just a little and get fluid enough to move and flow into tiny little microscopic crevices on material. When you stop applying pressure, the hairs stiffen up and get hard - just like holding onto a cliff with your fingertips.

The amount of pressure required to make the glue into a fluid is one property that gets measured. How strong it is attached to a surface before it detaches is another.

tl;dr it's very much similar to Velcro hook-and-loop material

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