Plastic wrap is stronger than steel!

[Iamme]

What do I base this evidence on? My super strong grip. Yet I am like the proverbial 97# weakling when it comes to trying to tear open some clear plastic wrapper that you might find wrapped around collector cards, or around certain candy or various other products.

It will slightly stretch, but you can't tear it. And it is only microns thick (so it seems). Yet, as odd as THIS is...what's even *more* odd is that if you just get a cut started in the edge of the plastic...it will then tear like butter. Who has the explanation for this?

[geni]

The reason it will tear very easly once you have small split is that after that all the force you are putting on the plastic is concentrated in one area ie. the end of the cut. the reason for the strengh of the plasic rapping will depend on what type of plastic it is made from.

[no one in particular]

Originally posted by geni
I love the smell of acetone in the morning Hey, I like acetone too! In fact, once in the now locked TTTWND! (http://www.randi.org/vbulletin/showthread.php?s=&postid=1869992284 ) I posted:Originally posted by no one in particular
Acetone has long been my favorite solvent. Sure, water is great, but acetone is the best. I enjoy the smell, the functionality and, most of all, the cooling effect it has on your skin. I would say that toluene is my third favorite, behind acetone and water. Four? I would have to say alcohol, then MEK as number five.Anyway, hey, lamme, put some acetone on those cd wraps. That'll take care of 'em.

[geni]

Originally posted by no one in particular
Hey, I like acetone too! In fact, once in the now locked TTTWND! (http://www.randi.org/vbulletin/showthread.php?s=&postid=1869992284 ) I posted:
Acetone has long been my favorite solvent. Sure, water is great, but acetone is the best. I enjoy the smell, the functionality and, most of all, the cooling effect it has on your skin. I would say that toluene is my third favorite, behind acetone and water. Four? I would have to say alcohol, then MEK as number five.

What about ether? Has the great advantage that when you spill it on the desk it just disapears.

Back to why packageing is so strong. The molicules that make up plastics are very long. This means that evern the weak atractice forces between them add up into a very stong subtance.

[Iamme]

(Two guys standing in the shower) Guy one to guy two: "....the reason being....my molecules are longer than yours!":bgrin:

Seriously...what else can you think of, that one wouldn't THINK should be strong, is, because of 'long molecules'?

[Dorian Gray]

You mean, you can tear steel?

[geni]

Originally posted by Dorian Gray
You mean, you can tear steel?
If you have steel as thin as thin as plastic rap you could do it. After all you can tear alium fiol without much difficulty and that has about 1/3 of the strength that steel that thickness would have.

[Iamme]

Seeeeeee?...Dorian Gray? It's a mystery, ISn't it?

Geni---I saved that particularly stubborn piece of plastic. After reading your post about how when it is torn a little to begin with, your tearing efforts are then focused at that tear...I thought I would try to tear the plastic, finger nail to fingernail...which then cuts down on any distance between, as to help concentrate your tearing effort to the area between your two fingernails. It still did no good. I couldn't tear it.

[MoeFaux]

Plastic wrap is stronger than steel

I don't know about that, but plastic wrap can be easier to wear. :D

[epepke]

Originally posted by Dorian Gray
You mean, you can tear steel?

You poor deprived kids, growing up in an age where there are no steel beer cans any more.

[Terry]

Originally posted by geni
The reason it will tear very easly once you have small split is that after that all the force you are putting on the plastic is concentrated in one area ie. the end of the cut.

If you are interested in reading about this in detail, I recommend "The New Science of Strong Materials" by J. E. Gordon. Stress concentrations are dealt with in chapters 4 and 5. It's a great read if you are at all interested in materials science. The math is kept to a very very bare minimum.

--Terry.

[baggie]

many plastics are easily as strong as steel on a weight basis if prepared well. It depends what you mean by strength. Stiffness: steel has a tensile modulus of about 200 GPa. Normal polyethylene is less than 2GPa, but it possible to ultradraw polyethylene (which aligns the chains along the fibre) to at least 200 GPa. As Steel is many times heavier than polyethylene, if you want stiffness and lightness, go to plastic composites.
Plastics are also tougher than many metals, e.g they can take ore knocks and damage before failure.

[Iamme]

Plastic wrap being stronger than steel...post by "baggie'. You're puttin me on, right? Baggie? Wrap?:D

[baggie]

not "wrap" as that tends to be polyethylene, and in a film it does not orientate well. The very high stiffnesses I mentioned have been obtained in fibres. The stiffness of most films is less than 1/100 that of steel.

Plastic films may be tougher than steel (absorb more energy before breaking) or have greater tensile strength (force needed to break). This is because steel tends to be very stiff but comparitively brittle compared to plastics. All three characteristics go into the "feel" of a strong film. E.g diamond is the stiffest material known, but very brittle as it has no give. Will dig up some figures on the tensile strengths of these materials later

[Zep]

Aluminium foil may tear easily, but it takes a 15-tonne rolling press (think big hot mangle) to make the stuff so thin. And a multi-tonne drawing pull (think mum pulling washing through mangle) to pull the foil through. It's TOUGH, all right!