Which is stronger: Glue or tape? - Elizabeth Cox
-
0:07 - 0:12The oldest glue in the world
is over 8,000 years old -
0:12 - 0:15and comes from a cave near the Dead Sea.
-
0:15 - 0:17Ancient people used this glue,
-
0:17 - 0:20made from a mixture of animal bone
and plant materials, -
0:20 - 0:24to waterproof baskets
and construct utensils. -
0:24 - 0:25And for thousands of years after,
-
0:25 - 0:30plants and animals were the glue
that held human civilization together. -
0:30 - 0:35Today, we have enough types of tape and
glue to build and repair almost anything. -
0:35 - 0:39But what gives glue
and tape their stickiness? -
0:39 - 0:42And is one stronger than the other?
-
0:42 - 0:44Adhesives can be made
from synthetic molecules -
0:44 - 0:47or natural proteins and carbohydrates
-
0:47 - 0:49like the vegetable starch dextrin,
-
0:49 - 0:51the milk protein casein,
-
0:51 - 0:54and the terpenes in tree resin.
-
0:54 - 1:00In order to work, glue and tape need
both adhesive bonds and cohesive bonds. -
1:00 - 1:04Adhesive bonds occur between
an adhesive’s molecules -
1:04 - 1:07and the molecules
of whatever it’s sticking to. -
1:07 - 1:11Cohesive bonds happen between
a glue or tape’s own molecules, -
1:11 - 1:13holding it together.
-
1:13 - 1:17Most glues consist of adhesive polymers
dissolved in a solvent -
1:17 - 1:20that prevents them from sticking
to the inside of the bottle. -
1:20 - 1:23The strong smell of many glues
comes from the solvent, -
1:23 - 1:26which evaporates when exposed to air.
-
1:26 - 1:29Some glues use water as a solvent,
-
1:29 - 1:33but others use chemicals
that can be harmful to inhale. -
1:33 - 1:38Glues with two or more components that
chemically react instead of just drying -
1:38 - 1:40can create stronger bonds.
-
1:40 - 1:43Both the adhesive and cohesive bonds
of glue are strong, -
1:43 - 1:47but the drying process
makes them irreversible. -
1:47 - 1:51This is why, if a glued surface
is broken after it dries, -
1:51 - 1:54it can’t be reattached without new glue.
-
1:54 - 1:58By contrast,
when tape is applied to a surface, -
1:58 - 2:00it forms weaker, reversible bonds,
-
2:00 - 2:05so you can peel a piece of tape off
a surface and use it again. -
2:05 - 2:08These weak bonds,
called Van der Waals forces, -
2:08 - 2:11can occur between any two materials,
-
2:11 - 2:14but only if they’re
extremely close together, -
2:14 - 2:16closer than the naked eye can see.
-
2:16 - 2:21Tape usually consists of a backing coated
with a combination of a rubber -
2:21 - 2:24or rubber-like "stretchy" component,
-
2:24 - 2:26and a compound called a tackifier.
-
2:26 - 2:29That’s the "sticky" component.
-
2:29 - 2:31A tape’s stickiness is determined
-
2:31 - 2:34by the proportion of elastic component
and tackifier, -
2:34 - 2:37the thickness of adhesive spread
onto the backing, -
2:37 - 2:39and the type of backing material.
-
2:39 - 2:44No chemical reaction occurs
when tape is pressed onto a surface. -
2:44 - 2:50Instead, the soft adhesive flows into
the cracks and grooves of the surface. -
2:50 - 2:57This ability to slide into cracks and then
stay in place is called viscoelasticity. -
2:57 - 3:01Once the viscoelastic adhesive fills
these microscopic crevices, -
3:01 - 3:05it is close enough to form
Van der Waals forces. -
3:05 - 3:09So what’s the world’s strongest adhesive?
-
3:09 - 3:11Well, there’s no one answer.
-
3:11 - 3:14In terms of absolute strength
of adhesive bonds, -
3:14 - 3:16glue is stronger than tape,
-
3:16 - 3:21but no single adhesive
works well in all circumstances. -
3:21 - 3:25Of the glues, cyanoacrylates,
or super glues, -
3:25 - 3:28may form the strongest bonds,
-
3:28 - 3:33but two-component epoxy glues have much
higher resistance to heat and shearing, -
3:33 - 3:37and are compatible
with a wider range of surfaces. -
3:37 - 3:40So, if you wanted
to dangle an anvil in the air, -
3:40 - 3:43super glue might be your best bet.
-
3:43 - 3:46But if you’re doing so
over an active volcano, -
3:46 - 3:48you’d want an epoxy instead.
-
3:48 - 3:50And in order to work at all,
-
3:50 - 3:53glues need enough real estate
where surfaces touch. -
3:53 - 3:56If for some reason you wanted
to make a chain of bowling balls, -
3:56 - 3:59duct tape would be better.
-
3:59 - 4:04Engineers weigh similar,
if less absurd, factors all the time. -
4:04 - 4:07Choosing the right glue to withstand
the heat inside an engine -
4:07 - 4:09is a matter of life and death.
-
4:09 - 4:12And though the strength
of duct tape’s adhesive bonds -
4:12 - 4:14can’t compete with those of epoxy glues,
-
4:14 - 4:19tape does have the advantage of
instantaneous stickiness in an emergency. -
4:19 - 4:22Glue may be necessary
to get a rocket to space, -
4:22 - 4:25but when it comes
to extraterrestrial repairs, -
4:25 - 4:30stick to duct tape:
liquid glues don’t work in zero gravity.
- Title:
- Which is stronger: Glue or tape? - Elizabeth Cox
- Description:
-
View full lesson:
The oldest glue in the world is over 8,000 years old and comes from a cave near the Dead Sea. Today, we have enough types of tape and glue to build and repair almost anything. But what gives glue and tape their stickiness? And is one stronger than the other? Elizabeth Cox explores the world of adhesives.
Lesson by Elizabeth Cox, animation by Sinbad Richardson.
- Video Language:
- English
- Team:
closed TED
- Project:
- TED-Ed
- Duration:
- 04:51
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Michelle Mehrtens edited English subtitles for Which is stronger: Glue or tape? - Elizabeth Cox | |
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Michelle Mehrtens edited English subtitles for Which is stronger: Glue or tape? - Elizabeth Cox | |
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Michelle Mehrtens edited English subtitles for Which is stronger: Glue or tape? - Elizabeth Cox | |
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Bethany Cutmore-Scott approved English subtitles for Which is stronger: Glue or tape? - Elizabeth Cox | |
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Bethany Cutmore-Scott accepted English subtitles for Which is stronger: Glue or tape? - Elizabeth Cox | |
![]() |
Michelle Mehrtens edited English subtitles for Which is stronger: Glue or tape? - Elizabeth Cox |