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A picture of the new super strong paper. Its strength owes to its small fiber size.  (Source: American Chemical Society)
Up in the sky -- is it a bird? Is it a plane? No, it's super paper!

Some people can get a little sick of hearing about carbon nanotubes.  Sure, the little structures are strong, and bear a plethora of uses, but they're still expensive, so unfortunately their uses remain in the future.  However, a new, more affordable technology has been developed which revolutionizes an everyday material and will increase its strength to surprising levels.

The new technology, developed by researchers at the Royal Institute of Technology in Stockholm, takes ordinary cellulose and puts it through special processing.  The end result is a paper, made out of normal wood pulp that has an incredible tensile strength of 1.6 times that of iron.  The paper sports 214 MPa of tensile strength, easily trumping iron (130 MPa) and heavy duty paper (103 MPa).  Tensile strength helps to measure how resistant a material is to ripping, and how much weight it can support.

The new paper is composed of nano-sized whiskers of cellulose.  Cellulose, the crystalline polymer of glucose, is what makes up cell walls and makes plants so rigid.  On a nanoscale, cellulose fibers beat steel and glass in strength, but paper is composed of larger cellulose strands that are prone to breakage under stress.  Typical commercial paper has a tensile strength of a mere 30 MPa, indicating its weakness.

To make super paper, researchers first had to make the cellulose fibers super small.  Head researcher Lars Berglund used enzymes and mechanical beating to tear the cellulose fibers to a mere 1,000 of their original size.  Then the researchers added carboxymethanol, which coated the fibers in carbonyl groups.  These groups produced hydrogen bonds, further strengthening the material.

The research was published in the current issue of Biomacromolecules.

Mike Wolcott, a materials scientist and cellulose fiber expert at Washington State University in Pullman, labels the paper as "quite interesting".  He notes that the paper has large pores between fibers.  These pores make it dry quicker, saving in production costs and making manufacturing easier.  John Simonsen, a physical chemist and nanocrystalline cellulose expert at Oregon State University in Corvallis, adds that the new material is formed from the most abundant organic material on the planet, so even with the extra treatment it should be cost competitive against more exotic materials like carbon nanotubes.

The new paper may be even used in medical uses such as providing scaffolds for growing replacement tissues or organs.  However its most practical application may be as simple as the shopping bag.



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RE: you know
By TennesseeTony on 6/11/2008 4:07:55 PM , Rating: 2
Tensile strength refers to it's stretching resistance.

As noted below, the tensile strength has nothing to do with the ability to cut this paper. The article makes no mention of any increased toughness, other than it's tensile strength.

I would personally assume though, that it would be a bit more resistant to abrasion and cutting, but not enough to matter, or the article would have mentioned those improved properties as well.


RE: you know
By masher2 (blog) on 6/11/2008 4:18:59 PM , Rating: 3
True, and cast iron itself is quite weak compared to many steels, which can be have tensile strengths up to six times higher. Cast iron is useful not because of its strength, but because of its castability and its extreme rigidity.


RE: you know
By Keeir on 6/11/08, Rating: 0
RE: you know
By Jimbo1234 on 6/11/2008 9:53:48 PM , Rating: 2
Cast iron has poor ductility. So while its compression strength is high, it's not so good when you try to pull it apart.


RE: you know
By Keeir on 6/11/2008 11:25:54 PM , Rating: 3
And where did I say its tensile strength was high?

Toughness is a measure of work of fracture. Which both cast and wrought iron tend to be better at then most high carbon steels. (note, High Carbon Steel are typically this High Strength steels with 450 MPa+ tensile strengths). Low Carbon and Medium carbon BOTH have better fracture toughness than High Carbon steels and depending the comparison of the materials better than cast iron and wrought iron.

Picking from matweb (A fairly good industrial source for material allowables)

http://www.matweb.com/search/DataSheet.aspx?MatID=...

This is Cast Iron Overview

http://www.matweb.com/search/DataSheet.aspx?MatID=...

Grey Cast Iron. A common type of cast iron, but no Toughness value. :( (Oh, btw, Grey Cast Iron type of cast iron has a Ultime Tensile Stress of ~250 MPa, which is better than many low carbon steels and significatly better than this paper)

The point I would like to make to people is this: Don't get all excited because in one direction (after all the material is probably highly orthotropic) this paper is fairly strong getting pulled. Depending on a whole host of additional material allowables will determine if this material is actually a good replacement for normal paper. Heck, tensile strength is not even really useful at all. A better one is tensile efficiency, tensile strength divided by density. (BTW, even the values on Matweb for Fracture Toughness are not particularly helpful in design. A better measure for material choice would be relative fracture toughness, fracture toughness divided by tensile strength)

A second point is the idea that High Tensile Strength correlates to High Fracture Toughness which is specifically mentioned in the article. I can think of numerous examples where the exact opposite is true. (7 series Aluminum Alloy Compared to 2 series Aluminum Alloy)

High Fracture Toughness IS slightly related to ducility. But a think a better way to think of this is that ducility indicates certain types of molecular bonds and grain structures. Some of these types of molecular bonds (And grain structures) have postive influence on fracture toughness and some of these don't.


RE: you know
By geddarkstorm on 6/12/2008 1:39:50 PM , Rating: 2
When using this stuff to make a box, tensile strength is going to be important I would think--how easy it is to rip the bottom out of the box due to too much weight pulling the strands apart. So, this new paper should be able to make much better boxes than normal cardboard. I think that's the point of it--what else do you use high strength paper for?

However, since some of its strength comes from hydrogen bonds, getting this stuff wet will probably make it quite weak as water competes for said bonds.


RE: you know
By Keeir on 6/12/2008 2:39:30 PM , Rating: 2
Actually, paper bags tend to have high degrees of "ripping" or crack growth. Usually a failure of an overloaded bag can be traced to a small tear or sharp corner poking into the paper bag. Its rarely a case of pure overload in tension.

Same thing is true for most current carboard boxes. Usually the tape or glue fails in shear before the box does or there is impact damage which degrades the capacity of the box.

Without knowing this materials resistence to impact damage and degree of "ripping" resistence, I don't know whether it would make a stronger box or bag in actual practice. Pure tensile strength is next to worthless.


RE: you know
By Jimbo1234 on 6/12/2008 1:50:52 PM , Rating: 2
You imply it with the use of the word structures. Tensile is what steel is mostly used for in rebar. It is highly desireable as concrete has nearly none. Shear strength is another desireable property such as in civil structures. So unless you define what exact structure you are talking about, and what environment, there is plenty of room for debate.

I'm quite familiar with matweb. However, matweb by itself is not the end all of material properties.

Also on a final note, thin films (such as paper) do not have the same material properties as the bulk material (e.g. test coupons) from which most Matweb values are derived.


RE: you know
By Keeir on 6/12/2008 2:34:10 PM , Rating: 1
Structure implies tension only?

Is a Column not a structure? Bridges (a structure) only have members in tension? Beams are not structure?

In reality, most structures are made of tension, compression, and shear members. ALL three.

Nor is straight material strength, be it in tension, compression, or shear, going to be over-riding consideration for use of a material for a purpose.

Steel rebar in concrete is very effective because concrete shields the steel from corrosion. Pure steel bridges, while being effective from a loads standpoint, do require significant maintaince

And, I am well aware of the differences between thin and thick geometries, yet the results specifically mentions "Tensile Strength".


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