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The Irrational Fear of Chemistry, Demonization of Plastics, and Some Thoughts on Extrusion

Is water natural or chemical? The answer is, it’s both. That bothers some people who see the two as opposites. If that applies to you and you work with plastics, please understand that everything is chemical, as chemistry is just a code system to describe all matter so people can understand each other, no matter what language they speak.

Natural usually describes anything found on Earth, such as the air, most minerals, and things that grow, like plants and animals. Some people argue that if we change a genetic structure we are making unnatural living things. But that matters more if you think natural is always better, which is belied by such undeniably natural things as venomous snakes, destructive hurricanes, suntanned skin, some but not all bacteria, and some infamous viruses (think polio or smallpox if you believe COVID was man-made).

Look at air, a mix of 21% oxygen (which we and all animals breathe in to live), 78% nitrogen (which plants need), 1% argon (inert), and small but important amounts of water vapor (humidity) and carbon dioxide. Water molecules have one oxygen holding onto two hydrogens, which is why we call it H-2-O, which we all need.

Sketch courtesy of Allan Griffoxygen and hydrogen molecules "holding hands"
Each oxygen has two “arms,” so it can hold two hydrogens that have one arm each, like a parent holding a child’s hand with each of theirs.

Our own bodies are made up of these three elements — O, H, N — plus carbon atoms, each with four arms, to hold it all together. Most plastics are the same, made of C, O, H, and N. Polyethylene is strings of -HCH-HCH-HCH-HCH-HCH-; PET has rings of C and some O, too; and PVC is like PE except with chlorine instead of one of the hydrogens. Chemistry is a simple code. No magic. In both plastics and people, a few other elements matter, such as iron and iodine in humans, magnesium in green plants, and chlorine and fluorine in some plastics.

Energy holds all these atoms together, conveniently forgotten when we talk about degrading and chemical recycling. Energy is what we want to conserve, and it’s measurable. But people want simplicity and are afraid to see how much fuel is needed to make the electricity for electric cars or how much energy is used in recycling.

Plastics often save more energy than they consume

Energy is needed to make plastics and to use them, too — by melting the pellets in extruders and molders, for example. But many plastics applications save more energy than they consume, disproving the common belief that making less plastic of all kinds is “good” for our environment, health, and food supply. Know the chemical structure of what you use, and the energy needs of competitive materials. It’s often easy to prove that plastics are kinder to us than alternatives. It’s much harder to convince a public that favors the natural, needs belief in magic to mentally survive, and may be your customers.

Additives are critical to plastics and are often irresponsibly maligned. Even the idea of additives is suspicious to the same people who may put cream and sugar in their coffee or tea, and butter on their bread. But that’s natural! Makes no difference until we see these additives as harmful. Two cases are notorious, and their myth-application is well-known — BPA and phthalates.

Fact: There is no BPA in your plastic bottle

BPA (bisphenol A) is not even an additive but a building block for a single plastic — polycarbonate, a tough, clear, expensive material used for airplane windows and CDs, a small percentage of the plastics industry and neither single-use nor litterable. However, people who think all plastics are the same have linked the still-controversial dangers of BPA to any tough, clear plastic, not just polycarbonate but even the PET beverage bottles that we have been using for 50 years.

A word about phthalates

The other myth is the word phthalate, a class of softeners (plasticizers) used for some vinyl (PVC) products (but no other plastic). It is often cited to support the belief that all PVC is bad, even uses with no plasticizers at all (like drain pipes and siding). The name sounds chemical, thus scary. The word phthalate is chemical code that comes from the Greek, but so do the words theater, elephant, theology, and zoo. And … plastic. There are many alternatives, and how much matters.

If you work with PVC (vinyls) you should also know the difference between orthophthalates and terephthalates (the T in PET) and know how that changes the behavior of the structure. Can’t find out? Please e-mail or call me. Understanding such chemistry is essential if you’re working with PVC.

Know the chemical composition of your additives

Most all plastic products include colorants and other additives. Some make the surface slippery or not. Fillers and inorganics can increase rigidity and opacity. Their particle size/shape and surface treatment and mixing conditions will affect their performance and may control their percentage. All these may have FDA status to govern their use in and around food; other geographic areas have similar systems. If you resent government interference, you need verified professionally agreed information to support what you do. This is no place for experiments or personal opinions, nor can we expect the public to have basis for its opinions.

Stabilizers and antioxidants help the plastic to remain unaffected by high process temperatures, and their use may also be regulated. There are many more types of additives — too many to list here — but whatever they are, I would want to know the chemical description of anything I put in my plastic. Just claiming a natural origin isn’t enough; the chemical code tells me what it is, and I can control how much of it there is.

Plastics chemistry is simple, easily learned, relevant, and useful, but often ignored or opposed by customers, politicians, and well-meaning but usually unspecialized chemophobes. You will make decisions based on many factors, but one of the hardest to manage is the need to reject the impossible. We don’t vote for the laws of science, and following them may mean less comfort, less power, maybe more cost, but it will lead to honest and possible progress.

Allan GriffAbout 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,, 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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