Polyethylene Possibilities?

Today, you can probably find polyethylene's friends on the short list. One of the simpler and earliest polymers, it has a lifetime of several hounded years - owing to its extreme stability. Almost nothing gets to it other than a bacteria that some kid found and presented as a science fair project.

Polyethylene is everywhere, and that's part of the problem! The estimated annual World production of polyethylene is 600 million tons!!! At least some of this production winds up as plastic grocery bags - the scourge of the environment! Owing to their lightness, strength, and chemical stability, they've been known to really cause troubles. For example, several floods have been attributed to drainage systems being accidentally clogged by these pesky bags. And more than one environmental group is lobbying hard for the end of plastic grocery bags - No paper, no plastic, just nice, reusable canvas. However, with all of polyethylene's problems, it does show some very interesting promise in the energy industry.

I bring your attention back to a thread that appeared on CR4 a number of months ago, specifically, Del the Cat's "Junkyard Battery Contest." I really got into that thread, and even after it basically died of old age, I continued to mess with the possibility of creating a cheap battery that would put out reasonable power at a very low cost. My design was to create two 1/2 cells that form a full cell battery. In this configuration, two dissimilar metals are submerged in a solution of their sulphate. For example, one 1/2 cell contained a piece of iron submerged in FeSO₄, and the other 1/2 cell contained a piece of copper submerged in CuSo₄. Each 1/2 cell is separated from the other by a porous separator. Here's where it gets weird...

The porous separator is very interesting in deed! It is a material that allows the charges from each solution to pass into each other, while at the same time it does not allow the two solutions to mix! A pretty neat trick!!! So, as I started development on my battery, I suddenly became aware that there are very few references to what exactly porous separators are made of. For instance, the "Battery Bible," an industry reference, mentions "porous separators," but not what they're made of. A few other references on the Web mentioned that the industry used wood at one time, then a type of paper (not specified), and several "sintered materials (again, not specified). I was getting nowhere fast in my hunt for separator materials!!! One hopeful possibility occurred in the form of the Gore Corp. web site (The folks that bring us Gortex™).

Core Corp. was willing to talk about their separator material based on Teflon™, and said that they would be happy to provide me a sample of their separator material... For $500.00. Woof!!!

After turning that little deal down, and with an almost complete lack of separator material information, I decided to start my own quest for a good separator material. So, very-then latex, no; very-thin vinyl, no; plastic wraps of various types, no; types of foam material, no; paper, no;... the list goes on. Each material I tried either would not pass the charges or would allow the solutions to mix, which killed the battery instantly. Then, with one double 1/2 cell box-set left, on a whim, I tried a square cut from a plastic grocery bag. At first, nothing. Then, within less than a minute my DMM was showing the exact voltage that should occur from the chemical reaction of iron and copper!!! Additionally, there was absolutely no mixing of the two solutions whatsoever! Wow!!! So I guess that's how science is really done!!!

So what did I learn from my experience other than how to construct a multi-cell battery? I believe I learned that one of the hardest things to develop is a really good separator material, and that those that do find a good one, tend to guard their information. You can always calculate the power that the chemistry will give you from a number of readily available tables, but finding the correct separator can take a company a long time to discover, and once discovered, they're not too willing to share that information.

So here's my final thought - Could polyethylene prove to be a good all-around porous separator material for batteries? Is it currently used extensively as such today? I do not know. Furthermore, one of the greatest problems in the fuel-cell industry is the cost of separator materials, these are calculated as the most expensive components of fuel-cell manufacture. However, if polyethylene is so chemically stable, as well as thermally stable (up to about 260° C), could polyethylene prove a viable separator material in fuel-cells? If yes, this would drastically reduce the cost, and bypass the the companies that may want to maximize profits at the cost of progress.

What does you's guys think? Any comments on this subject would be welcome. My discovery of polyethylene as a good separator material may have been an exercise in re-inventing the wheel. I don't know, you tell me!!!