GriffsNotes: Plastic Is Not Toxic, So How Can It Be a Pollutant?
Allan Griff | Aug 13, 2023
When I was a little kid — We all were once, think of that! — August was a nothing month. No school, no major holidays. Nobody went on vacation, and nobody had cars. We did have the beach, though, where I went with Mommy every day and where I did my first engineering projects involving wet sand and clam shells. She got her needed physical rest but had to stay alert lest I get too close to — or even in — the ocean, home to the clams whose 3-x-4-inch shells I used for building walls. Now I live about the same distance from the other ocean, and visit fairly often, but nothing goes into the water except certain breeds of dogs. And we go by car. There’s no community shower, no clamshells, few little kids, but there are trees to sit under and magnificent views of high civilization and nearby green-topped hills.
Across that ocean, the distance to Tokyo is over 5000 miles. All seems flat except for the waves. Down below, it's big and bumpy but very little fun, especially for us air-breathers. PET water and soda bottles sink when they meet flowing water, and maybe never make it to the sea at all, despite the image of their polluting the fish we eat, and the need to believe that by 2050 there will be more plastic in the ocean than fish.
And what's on top is everything that floats, which includes a lot of wood and single-use PE bags and some PP fishing line and netting. Sunlight will break their polymer chains into microplastic bits, which are indigestible and far too big to circulate in the blood of fish or us.
As for plastics polluting the ocean, since plastics are not toxic, there is no pollution, right? Wrong, as the popular and chemiphobic image of toxic plastics has swept the world. Not just among the activists but almost everyone, as it's easier to believe plastics are bad than to follow the science-based and logical understanding of polymer chains and their energies.
Science says no magic, no miracles. It also says, measure and count. Count energy, not pounds of plastic or gallons of petroleum. It takes energy to hold atoms together and to make competitive materials like paper. It's not a choice — the rules of science hold whether we like them or not.
In August it’s OK to think, so we can see that the toxic image doesn’t cost us very much. We can fill the critical needs like medical and food-making (irrigation, fishnets, and ag film), scramble to look green, and keep using plastics where they are beneficial, including in food packaging. Brands invest in images — that’s what ads are for — so I’m not surprised we don’t fight the myth-information. Instead, we use language, but we should identify our materials more precisely, even with initials like PE or PET, and avoid the generic term plastics. Avoid synthetic or chemical, too. Don't get conned by natural (many harmful naturals) or organic (various definitions).
Understand our problems, even if they are related to the bad image. Beware the money-based belief that new or modified equipment will solve a problem. Sometimes it will, but I need to know how/why; how success is defined; who sets dimensions and metals, costs, and expected delays; and if a changed formulation or conditions can prevent delays and save costs.
In understanding energy, don’t assume motor energy is the only input. Energy is needed in barrel and die control, and in most cooling and product handling. And if you are using, buying, or considering “advanced” recycling, remember that you lose some or most of the energy used to form the polymer chains. You can use the polymer atoms again, but there is an energy loss that may be comparable to making new plastic. Collection and separation costs are well known, but the loss of atom-atom bond energy is not.
Changing product specs such as temp or pressure resistance may solve problems, too. This may lead to material changes and related changes in cost and time. Numbers — how much — matter. With additives, the amount depends on particle size and mixability, and not only on percentages. Pay attention to particle size, as finer additive particles may allow less additive and save money that way.
Even though they are nontoxic, the popular image wants plastics to disappear and many people see degradability as just that. Matter doesn't disappear, but that's science and is ignored when necessary. We can make almost any plastic degradable with additives — plant origin matters, but isn't enough. If it floats in the ocean like the PE bags, sunlight will degrade them. You may not need an additive at all, but the value is lost. I would expect sun-degraded (oxidized) PE to sink, but I'm not sure. Warning to Googlers: You can find whatever you are looking for on the internet, so get two or more sources who say the same, know the sources, and expect some misunderstandings and even impossibilities. For example, people confuse ortho- and tere-phthalates, PVC with PET, find BPA where it does not exist. One article said that PET leaches out antimony, a valuable metal used as an oxide in flame-retardant building products. Antimony has been used in PET polymerization catalysts, but amounts in bottle contents are very low, and it may not be used by all (or any) resin makers now. How much matters. I'm far more worried about viruses than about antimony in PET. Back in the real world, black PP trays may have enough filler to make them sink. If they sink in the ocean like all PET bottles/trays, the value is still lost to us but it will degrade more slowly. Not forever.
On land, this alleged ocean trash is mostly inaccessible as garbage/landfill, but where accessible at reasonable cost, it's best used as in-plant mechanical recyclate, or even sold commercially for uses where recycled content is required. Energy savings if mechanical and with no broken chains may still make it better environmentally than alternatives. There are definitions of degradable and compostable, but they may not consider total energy costs, including growing plants, separating and joining atoms, melting glass, or making paper. So, if you swim in that ocean, know the standards. And if you really want to be environmentally responsible, know the energies and expect to be unpopular.
As for the real ocean, it has around 3.5 to 4% by weight of sodium chloride (common salt) and a much smaller percentage of other salts. Know the difference between chlorine the element and chloride the ion, easily confused by the PVC critics, and that chlorophyll, the substance that makes plants green, has no chlorine in it at all! The connection — the Greek root for the color green is chloro, and chlorine is a green gas.
About the author
Allan Griff is a veteran extrusion engineer, starting out in tech service for a major resin supplier, and working on his own now for many years as a consultant, expert witness in law cases, and especially as an educator via webinars and seminars, both public and in-house, and now in his virtual version. He wrote Plastics Extrusion Technology, the first practical extrusion book in the United States, as well as the Plastics Extrusion Operating Manual, updated almost every year, and available in Spanish and French as well as English. Find out more on his website, www.griffex.com, or e-mail him at [email protected].
No live seminars planned in the near future, or maybe ever, as his virtual audiovisual seminar is even better than live, says Griff. No travel, no waiting for live dates, same PowerPoint slides but with audio explanations and a written guide. Watch at your own pace; group attendance is offered for a single price, including the right to ask questions and get thorough answers by e-mail. Call 301/758-7788 or e-mail [email protected] for more info.
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