Packing tape not sticking? A troubleshooting guide for the line

A carton sits on the dispatch floor with its top flap standing up and a strip of tape hanging from one side. The first reaction is to blame the tape.

Sometimes the tape is the problem. Just as often, the cause is the carton, the weather or the way the tape went on. We make packing tape in Jaipur, so I have every reason to defend the tape. I would still rather you find the real cause.

In short, packing tape fails to stick for five main reasons:

1. A dusty or highly recycled carton surface.
2. Cold tape or cold cartons.
3. Too little pressure when the tape goes on.
4. An adhesive type that does not suit the job.
5. A fault in the dispenser or the sealing machine.

Old or badly stored tape is a sixth. Each cause leaves a different sign, and a few simple tests on your own line can tell them apart.

None of these tests needs a laboratory.

I have written this guide for supervisors and stores staff who need to fix the problem today. It does not teach basic taping. It assumes the tape is already being applied in the usual way and is still failing, particularly on a busy dispatch line.

First, look at how it fails

Look before you change anything. The way the tape fails tells you where to search.

Examine the paper fibre on a good carton too. A well-bonded strip of carton tape, pulled off a day later, will usually bring some paper fibre with it. A clean strip from the problem carton tells you the adhesive never really took hold.

Cause 1: dusty or highly recycled cartons

A sticker on a dusty steel almirah falls off within a week. Wipe the almirah first and the same sticker stays for years.

Tape on a carton works the same way.

Recycled board can carry loose fibre and dust on its surface, and cartons stored open near a dusty floor collect more. The adhesive sticks to the dust. The dust is barely attached to the board.

Tape manufacturers treat this as a known problem. Intertape Polymer Group's carton sealing tape brochure (2022) recommends its natural rubber adhesive for high recycled content cartons and dusty or dirty conditions. 3M sells a tape made for recycled corrugate (data sheet revised September 2024).

On highly recycled board, I would rule out dust before anything else. To test for it, press a strip of clear tape firmly on the carton, pull it off and hold it up to the light. A grey film on the adhesive is dust and loose fibre. Do the same on a fresh carton and compare.

The fix is partly in your godown. Keep cartons covered and off the floor. If the board itself is dusty, ask your supplier for a tape with more adhesive or a more aggressive adhesive type. Ask us too, if you buy from us. We would rather recommend a different tape than watch your cartons open in transit.

Cause 2: cold tape or cold cartons

Adhesive firms up as it gets colder. 3M's data sheet for its 371 carton tape (September 2024) notes this as temperatures approach 0°C, and says the tape goes on most easily at room temperature. tesa makes the same point in its article on why tape does not stick (updated May 2024).

In India this shows up on winter mornings in north Indian godowns, and wherever cartons are packed in or next to cold rooms.

To test it, measure the temperature of the carton surface and of the roll. A simple infrared thermometer is the easiest tool. Then seal one carton with a roll that spent the night in a warm room and one with a roll from the cold dock.

If the warm roll works, store the next day's tape and cartons indoors overnight, as the guide on storing tapes and films explains. If cold is unavoidable, ask your supplier whether the tape has been tested at your temperature. ASTM D3889 is a pass or fail test of tape adherence to linerboard at low temperature. Intertape's brochure lists separate cold temperature grades of hot melt tape.

Cause 3: not enough pressure

Pressure sensitive means exactly what it says.

The adhesive needs pressure to flow into the surface, especially on rough or uneven board.

Even the laboratory test presses the tape down before measuring it. IS 8402:1987, the Indian test method for these tapes, rolls a 2 kg roller over the tape before any peel test.

On the line, a packer in a hurry can lay the tape on without rubbing it down. On a machine, worn or badly set pressure rollers do the same thing.

The test is quick. Seal 10 cartons in the usual way and 10 with a firm rub of the hand along the full length of the tape. Check both groups after 24 hours.

I would run this one first. It costs nothing.

Cause 4: the wrong adhesive for the job

Carton tapes come in three main adhesive families. They behave differently, and the right one depends on the carton and the operating conditions.

Ask your supplier which adhesive your tape uses. It is often not printed on the carton, and I would want it written on the quotation.

Cause 5: dispenser and machine faults

A hand dispenser has three parts that matter here: the brake, the roller and the blade.

1. A brake set too tight makes the packer pull hard, and the tape stretches as it goes on. Stretched tape tries to shrink back and pulls at its own ends. tesa's advice is plain: do not stretch tape before you place it.
2. A worn or adhesive-coated roller presses unevenly.
3. A blunt blade leaves ragged ends, and ragged ends lift first.

I suggest you keep a spare blade and a spare roller near every packing table. They are inexpensive, and they remove two variables immediately.

On a carton sealing machine, examine the tape path, the pressure rollers and the length of the tab left down each side of the carton. A tab that is too short has very little to hold on to.

Change one thing at a time. Otherwise you will never know which change fixed it.

Cause 6: old or badly stored tape

Check the month of manufacture on the carton. Look for sticky roll edges or a funnel-shaped roll.

Then seal the same carton with the suspect roll and a fresh roll from another batch.

If the fresh roll works and the old one does not, the problem is age or storage. Find out how long that roll sat in your store, and where.

When the carton is the real problem

Some failures look like tape failures but actually start with the box.

1. An overfilled carton pushes its flaps up all day. That is a constant load on the tape, which is what holding power measures. The guide on reading a tape data sheet explains that number.
2. Varnished, coated or heavily printed board gives the adhesive a smoother, harder surface. Intertape lists heavy ink coverage among its problem applications.
3. Cartons that took up moisture in the monsoon are softer and weaker at the surface.

In these cases a change in the carton, or in how full it is packed, can do more than a change of tape.

A line test you can run in one shift

If you are not sure which cause you have, this test separates most of them.

1. Take 10 problem cartons and 10 clean new cartons.
2. Take one roll from the batch in question and one fresh roll from another batch, both kept at room temperature overnight.
3. Seal half of each group your usual way, and half with a firm rub along the full length of the tape.
4. Note the room temperature and the carton surface temperature.
5. Check every carton after 30 minutes and after 24 hours. Peel one strip from each group and look for paper fibre.
6. For a rough holding test, stick an equal length of each tape, about 5 cm, to the side of a carton and hang the same weight from each free end (a 1 litre water bottle, about 1 kg, is enough). Note how long each one holds. This is a home version of the fibreboard procedure in ASTM D3654, and it is only fair if both tapes are tested side by side, in the same conditions.

Reading the result is simple.

If clean cartons pass and problem cartons fail, the carton is responsible. If the rubbed group passes, the application pressure is the problem. If the fresh roll passes, examine your storage. If everything fails, the adhesive probably does not suit your job. Take the results to your supplier. I would expect any good supplier, including us, to take them seriously.

What to send your supplier

Whoever your supplier is, these five things will get you a faster and more accurate answer:

1. The batch number and month of manufacture from the carton label.
2. Close-up photos of failed tape ends, and of the carton surface.
3. The temperature where the cartons were sealed.
4. A sample roll and a few empty cartons from the same lot.
5. The tests you have already run, and their results.

Some jobs have no perfect tape, and I would rather say so than pretend. A cold, dusty, highly recycled carton sealed by hand in a hurry will test any adhesive, ours included.

If you are our customer, send us those five things through the contact page. We will tell you which cause looks most likely, even when the answer is the carton and not the tape.