Thursday, December 20, 2012

Copper Thieves Foiled by Plastic

Copper thieves have been active for the past 10 years or so, stealing copper pipes and tubing whenever and wherever they get a chance. Although copper prices peaked back in 2008, there is still enough opportunities for ne'er-do-wells to make a quick buck. Copper is fairly dense (the specific gravity is just under 9), so a little goes a long ways.

Contrast this with plastic tubing. The specific gravity is around 1, give or take (PVC is 1.4), so you need to steal 9 times as much just to have the same mass, and then the pricing is not so favorable either. Locally, scrap copper is going for about $3/lb, (~ 5€/kg), while scrap plastic is far less than a buck a pound. So, 1/9th the mass at say a fifth the price is not a good deal for even the most thick-headed of thieves looking to make a quick buck.

I mention all this as there was a local report yesterday that thieves had stolen copper tubing used to cool an outdoor skating rink here in St. Paul. The tubing will now be replaced, but with plastic tubing. And not just any plastic tubing, but crosslinked high density polyethylene (xHDPE). The crosslinking is great at toughening up the polymer, but worse yet, it makes it very difficult to recycle [*], meaning that even if it is stolen, no one will buy it.

It is important to understand this aspect of the polymer's chemistry, as the statement in the article, "The plastic-based composite material...has little to no scrap value..." could be taken as a broad-brushstroke about recycling plastics in general. Such a generalization would not be true, something I've written about in the past. Plastics can be cost effectively recycled and the demand for recyclable plastics is growing every year. Just not for xHDPE.

[*] This is why recycling tires is so difficult too - the crosslinking prevents the tires from being remelted.

1 comment:

Bend said...

Can crosslinked polymers be burned for electricity generation on large scale?