Plastics are Forever

Doesn’t have quite the same ring to it as “diamonds” does it? Besides, that’s the beef with plastics—they last forever! Diamonds do too, but that’s the appeal. With plastics we really want them to go away when we are done with them. Pesky buggers like to stick around, and even when they fall apart into little plastic bits they still last forever.

Recycling is the Holy Grail of plastics. There are too many kinds right now and they are too hard to sort and separate. When you melt down a mix of plastics into a goo you get a new plastic, not what you started with, and that’s not the intent of recycling.

plastics_waste_management_1960-2015_final

You can see we have a growing problem. Some have suggested we replace petroleum-based plastics with bio-plastics that will degrade after use. So far the materials tested are heavier, costlier, and less durable than what we have. The reason we use so many damn plastics is that they work! They are light, cheap, and tough, and have applications in so many areas in our lives that we would literally be lost without them.

The solution to any waste problem is to plan ahead. Manufacturing is traditionally a one-and-done affair. You get some raw materials, you stamp out your widgets, you sell them and send them away. If you make money you do it all over again.

In today’s world we ought to think about the end use and recovery of the materials before we make anything. That way we have a plan in place for the waste stream. In fact it is not a waste stream at all but a resource. The glass, aluminum, and steel industries all count on a significant portion of recycled scrap in their production processes.

The geniuses at Lawrence Berkeley Lab are looking to do the same with plastics. The Molecular Foundry has been experimenting with this stuff called poly-diketoneamine (PDK) that may do the trick. Plastics weren’t built to be recycled. Plastics made from this stuff are, however.

All plastics are polymers, made up of smaller, repeating units called monomers. The base materials are the same (hydrocarbons) for all plastics but it’s the additives that determine the different properties. These additives make the various types of plastics incompatible with each other when it comes to recycling. Once added these chemicals can’t be un-added and those polymers can’t be broken back down into their constituent monomers.

It is different with PDK plastics. The bonds are reversible and the end-use plastics can be broken down and the original monomers recovered and formed into new plastics again. The linear path of creation to use to disposal now becomes a circular one of creation to use to re-use. Now that’s a “forever” plastic!

I remember once talking to a nuclear engineer about the nuclear waste problem. He thought it was a mistake to bury the wastes too deep. He didn’t want the stuff to be too hard to get to. He said “we might need it later.” It was not something I’d heard before. He talked about all the energy and human ingenuity that went into the extraction and processing of these materials and what a shame it was that we would throw them away when done with them. The fact that they were still radioactive, to him, was a good thing. That meant they still had value.

I sure liked his perspective. We need more thinking like that.

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