By Deborah Parker
Americans love soda. In fact, some 450 million pounds of plastic soda bottles are collected at the nations recycling centers every year. While most consumers probably think that those bottles are washed and melted down and turned into soda bottles again, That’s actually not the case, says University of Massachusetts Amherst polymer scientist William J. MacKnight. Because the recycling industry cant guarantee that a consumer didn’t store insecticide or gas and oil for the lawn mower in one of those two-litre bottles before it ended up on curbside, reusing the plastic for continued food storage has always been out of the question. There was also a very slight degradation of the plastic during recycling, just enough that reusing it in a thin-walled container might render it not quite as strong a second time around, not strong enough to hold liquid under pressure.
That’s why the traditional fate facing these hundreds of tons of used polyester has been reuse in the manufacture of items requiring only low-end raw materials used in thick applications, things like the hardy park benches now dotting the nations parks. But this soon begged the question, just how many park benches does the world need? MacKnight continues. We wanted to explore if there wasn’t some way we could learn to reuse these polyester molecules, trapped inside as it were, in more high-end products, products that were currently requiring virgin raw materials, MacKnight notes. We recognized that any success would thus both reuse and reduce two of the environmental maxims.
With funding provided by NETI and the corporate support of G.E. Plastics, MacKnight and his students at the Silvio Conte Polymer Research Center at UMass Amherst soon learned that indeed, soda bottle polymers could be depolymerized treated and melted back down into a plastic syrup. The consistency of the new syrup was identical to that of the various polymer liquids manufacturers blow into the molds used to make everything from computer consoles to vehicle dashboards.
The soda bottle team was soon confronted with a serious, chemical engineering dilemma. They discovered that while one of the polymer components the trimer could indeed be melted back down, it did so only at 500oF, a temperature that destroyed the only existing re-hardening catalyst. Preliminary research into various methods of filtering out that one component, allowing manufacturers to use the rest, was immediately explored, but the idea was soon discarded as too expensive. Nobody was going to switch to the new material if it had a whole new set of costs associated with it, MacKnight acknowledged. A year later, however, the research team is grinning ear-to-ear. We discovered a new catalyst, one that will work at the higher temperatures MacKnight says cheerfully. Our patents are pending.
Roger Kambour, a research scientist with General Electric, says the ramifications for the plastics industry are fairly enormous. Every manufacturer of vehicle components be they cars, airplanes or boats should soon be knocking on MacKnights door, since the new thermoplastic components appear to be as hardy as the fiberglass material currently in use as car fenders and vehicle cross-beams, Kambour notes. For starters, the current manufacturing processes require the use of solvents that are both toxic and expensive, Kambour explains. This has meant that different manufacturers have had to safeguard their employees during the manufacturing process to begin with. Then, they either had to incorporate the solvent into the product, and thus lose it not to mention having to worry about the potential release of toxins should the impregnated material be involved in a hot-enough fire. Or, they had to go through various steps to evaporate the solvent off, and attempt to reclaim it. Both are expensive, Kambour concludes. The amazing thing about the new catalyst is that it allows scrap polyesters to be melted down, into a low viscosity fluid that can be injected molded and reacted in place, without the use of any toxic solvents at all.
What’s more, at the end of the life span of the traditional thermoset resin components, end products can only be discarded, they cant be melted back down, period, Kambour notes. MacKnights new thermoplastic, however, seems to hold the promise of being capable of repeated meltdowns. This means it could be salvaged in an auto yard, and used to manufacture things like shipping pallets. Then, if those were damaged, they could be returned, melted down, and remolded, again and again. MacKnight says the Polymer Center is now simply waiting for some major players in the polyester industry to step forward with some R&D pilot projects to test the properties of the scrap poly goo. He doesn’t expect to have to wait too long.
The problem facing us is that most companies are doing fine with the processes they have in place, and unless something changes new environmental mandates banning their current solvents, they think, why rock the boat?. The answer is, we have developed a new chemistry that will allow plastics manufacturers to use their current plants, give them significantly lower cost, produce a superior product, and have zero environmental impact, MacKnight concludes with a smile. It wont be long before somebody says, hey, wed be crazy not to.
The new catalyst promises to allow automakers, even airplane manufacturers, a solvent-free way to build strong and lightweight, and thus fuel-efficient, components for their vehicles. The resulting thermoplastic does not have to be ground up or discarded when a product becomes old or damaged; it can be melted down and re-used numerous times. Researchers believe the new technology can be used with existing machinery, will cut costs, create a better product, and have zero environmental impact.
The amazing thing about
the new catalyst is that it allows scrap polyesters to be melted down into a
low viscosity fluid that can be injected molded and reacted in place, without
the use of any toxic solvents at all.
Dr. Roger Kambour
General Electric