New plastic becomes stronger when stressed, drop-proof smartphones incoming

Extreme Tech

Plastics are amazingly versatile materials, and their usage in all manner of objects is only increasing. Virtually everything you own is at least partially composed of plastic, and that’s usually a very good thing. Plastic is light, inexpensive, and can be molded in any shape. However, it’s not always the strongest material. Many smartphone owners know the sorrow of dropping a phone and finding the fall cracked or chipped the casing. A new type of plastic developed at Duke University could change all that. This material actually gets stronger when it is stressed.

When the polymer chains are tugged or experience shock, they tear on one side. Other plastic polymers would not be so uniformly damaged, leading to structural failure. However, this is only the beginning of the transformation. The shearing force breaks the triangle into a longer chain, which also frees up bonding sites at the bromine locations for a second molecule to come in.

Link to paper:
Mechanochemical strengthening of a synthetic polymer in response to typically destructive shear forces

High shear stresses are known to trigger destructive bond-scission reactions in polymers. Recent work has shown that the same shear forces can be used to accelerate non-destructive reactions in mechanophores along polymer backbones, and it is demonstrated here that such mechanochemical reactions can be used to strengthen a polymer subjected to otherwise destructive shear forces. Polybutadiene was functionalized with dibromocyclopropane mechanophores, whose mechanical activation generates allylic bromides that are crosslinked in situ by nucleophilic substitution reactions with carboxylates. The crosslinking is activated efficiently by shear forces both in solvated systems and in bulk materials, and the resulting covalent polymer networks possess moduli that are orders-of-magnitude greater than those of the unactivated polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like biological materials, actively remodel locally as a function of their physical environment.

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No link yet, guess this just came up lol.


Interesting title to say the least, stronger when stressed, eh?

I really could use this on a phone, and I have friends with children who really really need it, they go through phones like toilet paper.

edit:


Sweet linkage.

When measured on the microscopic scale through a technique called nanoindentation, scientists found that the hardness increased by 200 times after the extrusion process. It even works when the plastic is dissolved in a solution.

Bring on the future

reply to post by atsmediapro


Where is the story, or at least a link ?

Interesting!

I double tapped the return key when entering the title and it submitted the thread before I had any content

Originally posted by atsmediapro
I double tapped the return key when entering the title and it submitted the thread before I had any content

okay, cool story wonder when they will start making cars out of this.

Question is, can it still be recycled like regular plastics or are we going to be experiencing a boom in indestructible garbage?

reply to post by atsmediapro

Polymerization is an interesting branch of molecular chemistry and this sound's like it may have many potential application's such as motorcycle helmets and knee pads but I would like to know more about how permanent the structural alteration at the molecular level is and how an new impact on the same area may affect it if dropped a second time, now if at ambient temperatures they could manage to make it so the molecules returned to there previous pre-impact state like a memory polymer then they would have created a genuinely marvelous thing but then they have still created something that has positive and practical safety applications.
S+F

reply to post by atsmediapro

It might be ok for specialized applications, like to make things which are handled in the vacuum of space unbreakable in the space program.

Personally I've dropped a lot of cell phones and none have ever broken so from my perspective they are talking about fixing something that isn't broken, and may be causing other problems.

The materials used in cell phones currently are reasonably safe. ABS and polycarbonate are two major plastics used in cell phones and they aren't easy to break, but they are stable.

On the other hand, this paper is talking about using a material which is intentionally not stable, so that new bonds can form on impact. This is probably not something we want for every day use, if there are safety concerns with the material, which I expect there are. The article talks about Polybutadiene, which even before modification does have some safety concerns with the monomer used to make the polymers:

en.wikipedia.org...

Acute exposure results in irritation of the mucous membranes, Higher levels can result in neurological effects such as blurred vision, fatigue, headache and vertigo. Exposure to the skin can lead to frostbite.[8]

Long-term exposure has been associated with cardiovascular disease, there is a consistent association with leukemia, and weaker association with other cancers.[8]

1,3 Butadiene is listed as a known carcinogen by the Agency for Toxic Substances Disease Registry and the US EPA.[9][10] The American Conference of Governmental Industrial Hygienists (ACGIH) lists the chemical as a suspected carcinogen.[10] The Natural Resource Defense Council (NRDC) lists some disease clusters that are suspected to be associated with this chemical.[11]

1,3-Butadiene is also a suspected human teratogen.[12][13][14] Prolonged and excessive exposure can affect many areas in the human body; blood, brain, eye, heart, kidney, lung, nose and throat have all been shown to react to the presence of excessive 1,3-Butadiene.

The polymers are of course safer, but as the source says the technology works by breaking bonds of the polymer, which would need to be carefully studied to see if it creates similar effects to exposure of the monomer.

So, I'd rather keep getting my cell phones made out of the materials they are already using. I don't have to worry about the material safety and I haven't broken a cell phone yet.