Sustainable Material Series: Environmentally-Friendly Plastics

In this multipart blog series, Dragon Innovation material expert, Nicolas Avril, will explore the pros and cons of selecting different materials when manufacturing a connected product in high volumes. This blog examines the use of environmentally friendly polymers. 

Polymeric materials are great. They can be stiff or flexible, transparent or colorful, block moisture or gases, be shaped to size through machining, injection molding, or other techniques, be reinforced with fibers, etc. No wonder they are now present in many surroundings. But plastic materials also seem to find their ways into places they were not intended for. This can be attributed to four characteristics of the common plastics of today. 

1. First, they are usually made from material, which took millions of years to come into being (i.e. oil). Using oil at the rate we are using it to produce plastic goods can only be a temporary solution. I would argue that if you can plan on acquiring a non-essential device, you should be concerned about whether your temporary enjoyment is worth sacrificing the well-being of future generations.
2. Second, they float and are often made in shapes that wildlife finds interesting. It can be because it resembles food (a plastic bag in water looks like a delicious jelly fish), or because it looks so irresistibly different (which animal would not want to stick its head through a six-pack holder?).
3. Third, the amount of time needed for common plastics to decompose is often counted in years. This, combined with the second characteristic mentioned above, results in a man-made problem. If plastics were to take a few weeks to decompose in the ocean or in the stomach of wildlife, the problem would be an annoyance, but not a life sentence. Again, the problem is not simply because plastics take hundreds of years to decompose (after all glass, ceramic, and metals also take hundreds of years to return to a "natural" state) but because they also do not sink, do interest wildlife, and fragment in small pieces as they decompose.
4. Fourth, they are inexpensive. And because they cost almost nothing, they encourage a throw away culture (sometimes even to the point of single-use).

So what are the material options for manufacturing a hardware product with plastic parts in large quantities in a sustainable manner? And what are the trade-offs and consequences? We will explore these further now.

Because recyclability can be approached from many angles, multiple words have been used and confusion exists around the meaning of some terms. Such confusion even allowed "greenwashing" to take place at times. It seems appropriate to first clarify some assumptions and definitions.

Recyclability 

Yes, a lot of common plastics (Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Polycarbonate (PC)) can be recycled. The issue is that the recycling center might not recognize the part as being made of the same material as a PE bottle, for instance, and might direct it toward a landfill. Also, as is the case with PC which has a recycling number of 7, together with a lot of other polymers, that lack of specificity makes sorting inadequate for efficient (profitable) recycling at many facilities (but combining Near infra-red (NIR) technology with Laser Object Detection (LOD) can help). 

And maybe the larger problem is that of human discipline. Currently less than 15% of the plastics created are recycled, and even in countries where such practice is part of the culture, that number is no more than 30%.

Biodegradability 

Strictly speaking, Biodegradability refers to the ability of things to get disintegrated (decomposed) by the action of microorganisms while getting assimilated into the natural environment without ecological harm during the process. There is no mention of time in the definition. So yes, since after a few generations most materials (including plastics) will be degraded, they are biodegradable. In other words, claiming that an item is biodegradable means nothing without providing the conditions under which it will biodegrade. 

The European EN 13432 standard remediates this and (among other requirements), puts some requirements after 12 weeks and 6 months. 

Bioplastics:

Depending on the background of the speaker and of the audience, this word can have many different meanings, thereby creating confusion at best, and greenwashing in its worst case. We will therefore follow the IUPAC recommendations and not use that word. Instead we will use one of the following.

Biobased polymers

This is used to refer to polymers composed or derived in whole or in part of biological products issued from the biomass (including plant, animal, and marine or forestry materials). Note that a biobased polymer or polymeric device is not necessarily environmentally friendly nor biocompatible nor biodegradable. Is it currently accepted that about 50% of biobased polymers are not biodegradable.

Compostable polymers

For a product to be labelled as compostable, the materials must disintegrate by 90% within 90 days of being in a commercial facility (in other words, if you dispose of them in the trash, which is what people commonly do, they won’t break down). In addition, they must create zero toxicity during the degradation process. If they don’t meet these requirements, they can’t be certified as compostable.

Note that compostable products don’t solve the world’s pollution problems. Without proper disposal, they’re as much of a threat to our oceans and wildlife as regular plastics because they don’t break down in nature.

Also, the form factor of the product made with a material will affect its "compostability." For instance, while PLA films under 20μm thick are compostable, films which are thicker than that do not qualify as compostable.

Biocompatible polymer

This is not discussed in this blog, however it is a polymer that is biocompatible (either through bio-indifference or through bioactivity).

Natural polymer

These are polymers of natural origin, produced within a living organism. They could be of the polyphenol type (for example the lignin found in wood) or the different types of polysaccharides (neutral such as cellulose, cationic such as chitin or anionic such as alginates). These are all compostable but creating objects with them is not yet mainstream. 

"Wrap-up"

When the time comes to select a plastic material, many options already exist to minimize our impact on the environment. From using additives made from biomass, to increasingly how "green" a material is, to using a compostable polymer created from organic wastes. And while some materials have an impact on the manufacturing process, this is not always the case. It is therefore important to consider the full Life Cycle Analysis. 

We'll dive deeper into other aspects of plastics and other material selection impacts in future blogs. If you have any additional questions feel free to get in touch.

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