The first thing is the broader use of the word “plastics”. Everybody defines it differently.
We talk about microplastics. A lot of the focus is on microplastics. The number one source of microplastics in the oceans is tire residue. The next top two sources of microplastics in the ocean are fibres—when you wash your clothes and they become lighter—and road markings. Most people lump that all in.
First of all, I think I have to narrow it down to say that there are a lot of man-made materials that find their way into the environment—and that's why I'm such an advocate of better recovery systems—that are defined as plastics. However, if we narrow it down to the ones that we're mostly familiar with, let's say the ones that are in a bottle or a particular package of materials, the most common materials used for packaging have been chosen because, first, they're medical grade. They're completely stable molecules. They're completely hygienic. They don't interact with the substance inside. That's why an aluminum can has a plastic liner, every one in the world; otherwise, there would be a reaction between the contents and the aluminum. That's the first reason.
The second thing is that there are about three grades of plastic that represent most of the things we use: PET, polypropylene, and polyethylenes. The thing that a lot of people don't appreciate is that they're very versatile materials. A bottle and a blood tube are made out of the same material. The heart stent that goes to correct in heart surgery is made out of the same material.
The first thing we have to appreciate is that there's a family of materials that are highly used, very hygienic and very recyclable.
Second, there's a category of what I would call “hybrid materials”. That's where you're mixing two types of materials, or let's say, overusing materials. That's why lightweighting and finding smarter ways to get the performance you need without these composite structures are part of what's a big focus in the industry.
Hopefully that helps a bit.