by Jeremy Faludi

Originally we had planned for the oPen’s case to be injection-molded out of plastic or other materials with plastic’s useful properties. We’ve since revised that (and I’ll describe what we’re doing now in another post), but I thought it would still be helpful to describe the process of choosing a good plastic and publish the data that would help other companies with similar products make their own choices.

What plastic is best to use?

Greenpeace has a helpful list of what plastics are the best and worst, and why. Biopolymers are the best, followed by polyolefins (PE/PP/HDPE) second, PET third, ABS / polycarbonate / polyurethane / polystyrene fourth, and PVC worst. Here are the details, from their site and others who have written about this:

• Biopolymers (called “bio-” because they are made from plant cellulose or starch, not petroleum) usually use the least toxic ingredients, do not release toxic gases or other substances into the environment during the product’s life, and certainly use the least fossil fuel for their manufacture. Some biopolymers are compostable.
• Polyolefins (PE, HDPE, LDPE are all polyethylene, PP is polypropylene) are the best petroleum-based plastics because they use fewer toxic chemicals than other plastics. They’re also very widely recycled (recycling codes #2, #4, and #5.)
• PET / PETE (polyethylene-terephthalate; in clothes it’s called polyester) is not as good as simple polyethylene because more additives are put into it (usually UV stabilizers and flame retardants), but it’s still widely recycled (recycling code #1).
• ABS (acrylonitrile-butadiene-styrene) and Polycarbonate (PC) are what almost all consumer electronic device cases are made out of–computers, cell phones, MP3 players, you name it. Some are just ABS or PC, most are a blend of the two. The ingredients for both ABS and polycarbonate are suspected to be carcinogenic, some are also mutagenic; polycarbonate uses nasty solvents in its manufacture. They are both perfectly recyclable but are rarely recycled in municipal systems because they fall into recycling code #7, “other”. Polystyrene (PS) has carcinogenic ingredients like ABS (both contain styrene), but is also damages human reproductive system. It’s also recyclable but not often recycled (recycling code #6).
• PVC (polyvinyl chloride), uses more toxic ingredients for its manufacture, because in addition to carcinogens like vinyl chloride, it also requires plasticizers to be flexible, and these plasticizers are more toxic than the base plastic itself. Besides the manufacturing hazards, dioxin and other toxins like DEHP (a plasticizer connected to reproductive illness) outgas, leach, and flake off PVC during its use in your home; when thrown away, these chemicals also leach into groundwater in landfills. This is why they are the worst on the list. They can be recycled (recycling code #3), but rates are generally low. The good news is they were never in consideration for our product anyway.

What plastics did we consider?

Bioplastics were the first choice. Researchers at the University of Warwick made cell phone cases out of a biodegradable polymer which comes with an embedded sunflower seed–just drop the case in the ground and it composts and releases its seed. NEC made a cell phone whose case was made out of the bio-plastic PLA reinforced with kenaf fiber. Both of these projects were groundbreaking and took extensive R&D to accomplish. They have yet to be duplicated by other manufacturers. PLA is being used by itself in many applications–mostly food packaging–and although it is still new to the market, it is quickly becoming the most successful bio-plastic. The more prosaic Nylon 11, which has been around for decades, is also a bio-plastic: it is made from castor bean oil. However, since it was not invented with ecological impact in mind, it is not compostable and is more energy-intensive to make than PLA.

Unfortunately Exbiblio is both on a very tight deadline (startup companies can only live off venture capital so long before they need to start selling product), which made it unfeasible to make up cutting-edge materials like University of Warwick or NEC. Exbiblio also has very tight engineering requirements for the oPen, which made it unfeasible to use off-the-shelf PLA or Nylon of any kind.

In the end, the engineering requirements dictated that we use polycarbonate or ABS. At first I was dead-set against that because they are recycling coded “other”, so almost no cities recycle them. However, the biggest impact of our little electronics device will be the circuit board, not the case, and we will have a takeback program with a strong incentive for users to send their old devices back to us. The companies who take electronics for recycling all recycle polycarbonate and ABS, so we can consider them recyclable materials after all.

Using recyclable plastic is not enough for us. We also plan to use recycled plastic as our material, so that we do not cause any new plastic to be manufactured, and so that we can prevent existing waste from going to landfills.

Using recycled plastic

Recycled plastic is trickier to use than virgin plastic, but not insurmountably tricky. In theory, any thermoplastic can be ground up, melted down, and reused infinitely without degrading. It’s not like paper recycling where the paper fibers get cut up during the recycling process and become less sturdy with each cycle–the molecular chains that make up thermoplastics are far too small to be cut up by recycling machinery. However, in practice injection molding plastic does stress the material, and recycled plastic has different properties than virgin plastic. The main difference is that when using it for injection-molding, it has a higher viscosity, so you have to tweak your process. Some studies have shown that you can use up to15-20% recycled content without affecting your process, but if you want to use 100% recycled material as we do, some adjustments will have to be made and some trial-and-error will be required to get it working properly. Even then, your reject rate will be higher (perhaps 5% rather than 2%); but this is a small disadvantage in the face of the large environmental (and also financial) gains made by using recycled material. Of the several people I talked to (both plastic recyclers and manufacturers), there was no consensus about whether polycarbonate or ABS or a PC/ABS blend would give the best results when using 100% recycled material. Since we would need to use polycarbonate for the oPen’s window (there is no clear ABS), it seemed best to use polycarbonate for everything.

The good news is that recycled plastic is very easy to come by, and cheaper than virgin plastic. When I called GE plastics, their sales rep said post-consumer resins are “nearly impossible” to find; they sell a 50%-recycled-content resin for $2.60 per pound which uses post-industrial waste instead of post-consumer. However, a quick look through the Thomas Register turned up a long list of companies that do recycled plastic in the US; many of them sell ground-up (“regrind”) polycarbonate and ABS for less than a dollar a pound, some as little as 60 cents per pound. The main trouble with this (and the reason that GE doesn’t do post-consumer plastic) is quality-control. Recycling companies get every imaginable color and grade of materials, much of it painted or coated, and not everything is ground up into exactly the same-sized chunks; their sorting processes have to be extremely good for their end product to be reliable and consistent. If you try to injection mold with inconsistent material, you end up with streaks through your plastic that are at the very least an aesthetic problem, reduce optical clarity in transparent parts, and can also be a structural problem, making the plastic easier to crack. However, quality control exists if you are willing to pay for it, and since brand-name virgin resins can cost $10 or $20 per pound, it is easy for a recycler to be competitive. At least one company I talked to, Maine Plastics in Michigan, promised their regrind is as good for injection molding as virgin, and that if the melt is bad, they’ll take it back and give credit for what you paid. As for aesthetics, any regrind can be dyed black, and that was our color of choice anyway, so that does not present a problem.

It’s surprising that more consumer electronics companies don’t make their products out of at least partially recycled plastic, given how easy it is to come by and how cheap it is. I look forward to the process of working with a contract manufacturer to use recycled plastic when we get to the manufacturing stage.