Wednesday, April 29, 2009

The other kind of plastic

Water bottles, grocery bags and many other common consumer containers are made from recyclable plastics called thermoplastics or thermoplastic resins.

When you head out to add things to your neighborhood or company plastics recycling bin, these are the kinds of polymers you're taking out to be melted down and molded into new products. And that's great. But what about the rest of the plastics? The ones without the little recycling arrows or numbers?

Most of these harder plastics, known as thermoset resins, can’t be easily recycled. Unlike thermoplastic resins, cured thermosets will not melt and flow. They will soften when heated, but they cannot be reshaped. These polymers, used in things like circuit boards, airplane parts, Bakelite electrical insulation and epoxy glue, decompose when heated. Most products made from these plastics end up as waste.

But all that may be changing, according to a New York Times article:

Chemists at the University of Groningen in the Netherlands have devised a thermoset plastic that, rather than decomposing, heals itself when heated. Writing in the journal Macromolecules, the researchers, Youchun Zhang, Antonius A. Broekhuis and Francesco Picchioni, say the material has the potential to be recycled and reused many times. ...The researchers demonstrated that the material can be shredded, melted and remolded at least seven times with no loss of mechanical properties. Their discovery, they say, adds to scientific understanding of the nature of self-healing materials, and with more research may eventually lead to the full development of recyclable thermoset plastics.

This discovery could add a whole new green dimension to businesses who produce or use thermoset plastics in their products or have significant amounts as components in their machinery or equipment.