The Engineering of Duct Tape

Duct

tape

was first developed in World War II to repair ammunition boxes and has since become essential for repairing anything, at least temporarily, including cars, wallets, industrial equipment and, most famously, spacecraft in the Apollo 13 mission to the moon. This makeshift carbon dioxide filter was held together by

duct

tape

. The makeshift filter was necessary after an explosion on board destroyed part of the life support system. To accomplish all this, the

duct

tape is surprisingly well designed to do three things. It sticks to a surface when a little pressure is applied firmly holds two objects together and will then be removed without leaving adhesive residue to show you the fabulous design of the masking tape I will immerse it in a liquid that separates it into its key components it only takes a few minutes and then I can remove the embedded fabric backing On the plastic backing tape, notice that the drops of the fabric create these white rings which is the dissolved adhesive and if I stir it a little I can remove all the adhesive from the backing, which which causes the liquid to become cloudy, as far as we can now see.

The three components, the plastic backing, the adhesive dissolved here in the liquid and the fabric backing, each are necessary for the proper functioning of the adhesive tape, first, the adhesive that covers the fabric, is a very unusual type. We usually think of adhesive as something like Elmer's glue. as a liquid, then as seen in this 8 hour time lapse, the drop of glue shrinks like Salt and evaporates until it dries and becomes solid. However, this would not make the tape work, we need the adhesive to stick when pressed a little. It doesn't apply or dry and stays firm while the tape is in use, but doesn't stick too much as we want to remove the tape with just a little force and not leave any residue.

Instead, the stickiness of a tape's adhesive comes from what is called a fire stickiness. Fire is a bit like the syrup used on pancakes because it is a liquid that spreads over the surface to be bonded, creating enough contact points that adhere to another surface, but a pinch of fire alone is not enough compared to a silver paper. with just adhesive to a piece of tape, the adhesive will set the paper but will add a little weight and will not contrast that with the tape, which can support for the same surface at least a weight of 5 pounds or 2.3 kg to create a adhesive.

For the tape, the adhesive is mixed with the strangest substance, a material that is like a liquid so that it can spread the stickiness of the fire, but it will be a solid so that it keeps the tape in place and holds a load, but it is also elastic so it can be removed. when necessary, here is a substance that meets those criteria, silly friend, it behaves in three ways depending on how quickly it deforms. This 40-hour time lapse shows how the gentle pull of gravity causes it to flow like a liquid. When I pull it quickly it acts like a solid on the brakes you see here A different fracture plane and lastly it can even bounce a material that behaves in these different ways is called viscoelastic material for grip tape is combined with a viscoelastic material , usually rubber to create an adhesive, let's see how It provides pressure-sensitive adhesion strength once applied and removability by taking a close look at what happens when a piece of tape is applied and removed.

As I press the tape, the now viscoelastic adhesive spreads like a liquid to completely cover the surface which is called a wedding. By placing the adhesive in contact with as much of the surface as possible, once in place the adhesive acts as a solid and secures the ends of the tape so it can support significant weight; however, it is the fabric embedded in the tape that provides strength. holds the weight, this fabric is probably cotton, but depending on the tape, it could be polyester or nylon glass filament. The fabric is woven with long fibers along the ribbon.

These are what support the weight and tension, and perpendicular to these fibers are bundles of fibers. These bundles are made up of very thin fibers this loose weave helps reduce manufacturing cost allows the adhesive to pass through the fabric and adhere to the backing instead of a layer of adhesive to secure the fabric to the backing and then another layer Above the fabric this close-up of the tape adhered to the glass slide shows the viscoelastic behavior this is the tape and this is its reflection in the glass at first the viscoelastic material resists being removed it stretches the filament then elastically detaches from the surface leaving the glass without residue in an Ideal World the removal of the tape leaves no residue of the adhesive here is a piece that I have lightly glued you can see that it only partially wets the surface when I remove it there are no residues left I am left with a clean glass but most of the time, especially with duct tape, it sticks too much here.

I pressed it hard and heated the tape to break down the adhesive, so when the tape is removed it leaves residue on the surface, which is called cohesive failure if you look at the tape. Just peel it back closely, we see some smooth sections of intact coating and many areas where the viscoelastic adhesive layer has been destroyed. This is where the viscoelastic material behaved like a solid and fractured. Here is the tape being removed from the glass slide. that the strands elongate again but instead of elastically jumping off the surface the viscoelastic material fractures the strands break leaving residue on the surface you can see that fracture even more clearly here in our studio we often use adhesive tape which is designed to leave no residue It is similar to the blue tape that painters use to achieve this, they add a layer of primer between the backing and the adhesive which increases the anchoring of the adhesive so it adheres better to the backing when peeled off and they also use one more layer thin adhesive. use an adhesive that is softer and more flexible and therefore less likely to have cohesion failures and, for some removable adhesive items, for example sticky notes, there are microspheres in the adhesive that decrease the amount of contact with the surface , generally all this increases the cost of the tape.

Generally speaking, masking tape costs three to four times the cost of ordinary masking tape, as we have just seen, controlling the adhesion of the tape is of utmost importance; In fact, a key element of

engineering

tape is to control its adhesion and only by doing that, the tape can be rolled into a useful paper if the tape sticks too tightly to itself, we couldn't use it too loosely, it is also a problem. This is a defective roll where the tape is not sticky enough and as you can see it telescopes. Now we move on to the plastic backing itself, it is not very interesting, it is just a piece of plastic, but on its surface is the most patented aspect, it is covered with a non-stick layer that strikes the balance between too sticky and not sticky enough to understand it. how these coatings work remember what happens when you apply the tape the adhesive flows to spread the adhesive evenly and moisten the surface this way by controlling the amount of this wedding we can control the stickiness well the exact formulation of this release coating It is secret the main ingredient is silicone, like in this stopper, a drop of colored water falls on the stopper because silicone resists wetting.

Compare this to a drop on the surface of glass. The water spreads, that is, it is well moistened to then create a non-stick layer with just the right amount of stickiness. Engineers apply a coating that contains a little silicone, neither too much nor too little to hold the tape in position, but allows it to unroll easily. You might think that the invention of duct tape was a triumph of the chemistry of science; instead, it developed. by the

engineering

method, make no mistake, chemistry was necessary to synthesize these adhesives, these adhesives were mixed with viscoelastic substances, but hey, we can explain adhesion at the molecular level, Vander Wal forces and the like.

There is no detailed scientific theory that designs an adhesive, in fact, pressure. Sensitive tape predates much of the most basic molecular understanding of adhesion tape. It has been mass produced since the early 20th century, when engineers developed and refined the tape without this knowledge. It is not surprising to remember that the purpose of the engineering method is to solve problems before we have complete scientific knowledge. Engineers address this lack of knowledge about what is happening at the molecular level by developing precise ways to quantify the unknown molecular forces that lead to adhesion. This is My favorite is a ramp used to quantify the stickiness of an adhesive.

Place a ball on top of the ramp, release it and the stickiness of the tape abruptly stops the ball. Engineers made a standard-sized ramp and carefully detailed its specifications and dimensions. Here are four types of tape in decreasing order of stickiness. Duct tape, duct tape, duct tape, removable duct tape, so using a mixture of chemistry as a tool, empiricism and a lot of intuition. Engineers develop tape adhesive that can be used to do almost anything, although there is one thing you should not do with tape, as stated inside this roll, do not use it. on flue chimneys, mufflers or exhaust pipes, so don't use them on a duct or anything like that.

I'm Bill Hammock, the engineer.