Replacing plastics


In the January 21 edition of Nature, a letter by a team of scientists from the University of Tokyo elaborated on the construction and uses of a potential replacement for petroleum plastics: hydrogel.

Plastic production today is one of the largest industries in the world, and plastics remain the material of choice for packaging, industry and technology. Indeed, the modern world couldnt exist without them. But plastics, like many things that define the modern world, such as automobiles and hair gel, use up lots of hydrocarbons. In a bid to find new materials that dont depend on a vanishing resource, University of

Tokyo scientists investigated the making of a material known as hydrogel, a substance made mostly of water and another surprisingly common substance: clay, in nanosheet form.

Hydrogels are gels made mostly of water and polymers. They are insoluble in water but also incredibly absorbent. Hydrogels arent anything new; we use them as components in medicine, diapers and even contact lenses. So far, no one has seriously considered them for industrial purposes since, according to the Nature letter, most scientists think of hydrogels as weak. And they were right; until now, researches manufactured hydrogel based on covalent bonding, a process which creates a non-transparent, brittle, nonhealing paperweight. Clay nanosheets solved the problems of brittleness, but required a lengthy and difficult manufacturing process.

The Tokyo scientists opted to skip the covalent bonding process altogether, and created a tough, self-healing hydrogel from water, clay nanosheets, a dendritic macromolecule (a large, branched molecule, like a tree) and sodium polyacrylate (a polymer used commonly in hydrogels, also fake snow and detergent). The result was a material described as having a large mechanical strength and able to regain a solid state after undergoing extreme stress. To put it simply: hitting this gel with a hammer will turn it to mush, but that mush will regain its solid state over time.

So, unless the scientific faculties Ive gained as an English major fail me, essentially the Tokyo hydrogel is like the liquid robot from Terminator 2.
Perhaps the most interesting property of the Tokyo hydrogel is its stickiness. Blocks of the hydrogel can be cut, pushed against other pieces of hydrogel and then become part of the new block. This only occurs on freshly cut hydrogel, and the resulting bond is as strong as if it were never broken in the first place. The gel is resistant to water and to organic solvents.

So, hydrogel sounds pretty neat. And its interesting to see whether its use in industry may replace conventional plastics, or even open up new avenues of production. Needless to say, an environmentally friendly alternative to traditional plastics in industry and in commerce would be a definite step up to lengthening the life of our civilization or, if theyre used to make terminator robots, will at least make our final moments really, really cool.