Norfolk Southern train 32N derailed in February in East Palestine, Ohio, while carrying chemicals and other freight. The presence of vinyl chloride and the actions taken to manage it made the derailment big news. Vinyl chloride is correctly described as flammable, toxic, and carcinogenic. It doesn’t sound like something that belongs in rural Ohio. So, why was vinyl chloride on the train? Pretzels are at least partially to blame.
Vinyl chloride was on the train because it had somewhere to go. The New York Times reported that the cars were headed to Pedricktown, N.J. The Pedricktown facility consumes vinyl chloride shipped in from vinyl chloride production facilities. Vinyl chloride is almost exclusively used for making polymers. It reacts when appropriately catalyzed, polymerizing into polyvinyl chloride, a plastic. Polyvinyl chloride, PVC, is by far the most significant use of vinyl chloride. Titanium Dioxide R6666
Most PVC production is located near vinyl chloride production, allowing transportation in pipes, not trains. That is true for the production of most polymers. The majority of monomers used aren’t shipped. Pellets of polymer are. Shipping vinyl chloride can be avoided by ceasing to make PVC in Pedricktown — instead making it at a facility adjacent to vinyl chloride production.
Why make PVC? PVC production consumes almost all of vinyl chloride produced. PVC is not a particularly strong polymer, softening at temperatures easily encountered. That makes it easy to process. It takes fillers well. It can also be made flexible by the addition of plasticizers. It can be clear — useful in many applications. It survives environmental exposure well, holds up to sunlight, and resists degradation. It is intrinsically self-extinguishing, a useful feature for wiring and construction applications. It is solvent-weldable, also very useful. And it’s cheap.
PVC does have issues. There is some residual vinyl chloride present that can escape. Industry dropped the amount of residual monomer through process improvements, but there is still some monomer outgassing. Plasticizer use in vinyl, especially phthalate esters, is problematic. The plasticizers leach out and have been implicated in bad health outcomes. When it burns, PVC creates hydrogen chloride, a corrosive acid. The production of vinyl chloride is also associated with the production of dioxins, persistent environmental pollutants.
We all use PVC, knowingly or unwittingly, every minute of every day. If you are connected to a municipal water supply, your water almost certainly passed through PVC pipes. Flip on a switch, and the power moves through PVC insulated wires. You’re likely walking on vinyl flooring, in your house or in commercial buildings. Medical applications include tubing and bags. Miscellaneous uses include consumer packaging, toys, and things like checkbook covers.
There are substitutes for PVC in every one of its applications, but PVC remains in the market because of its value. A complicated supply chain makes it pretty much impossible to stop making PVC. We produce PVC because it is hard to stop. PVC is a major product of one of the foundational technologies of the chemical industry, the chlor-alkali process. It is a coproduct process. Fortunately, Seinfeld stands ready to explain coproduct processes. Muffins are a coproduct process. The good-to-eat tops come with unappealing stumps. If you make tops, you get stumps. The chlor-alkali process makes both sodium hydroxide — also known as both caustic soda and lye — and chlorine. Our world is acidic. A chemical base is needed to neutralize acids. Sodium hydroxide is the base of choice, the highest volume industrially produced chemical base. The prices of caustic soda and chlorine fluctuate. Some of the time, caustic soda is more valuable. It is the muffin top and chlorine is the stump. Other times, the chlorine is the top and caustic soda is the stump. Whether top or stump, caustic soda is always needed. It is used in many processes. Without it, there is no aluminum. No titania. No paper. No bleach. Caustic soda is used in water treatment, textile production, soap and detergent production, and food processing. It is used to make baking powder necessary for muffins. Pretzels are crunchy because they are treated with sodium hydroxide before baking.
Vinyl chloride found its way to rural Ohio because it plays an important role in modern society. Talk of bans on shipment of hazardous material, talk of bans on PVC, ignore society’s appetite for the polymers and related, important products. We all, either directly through the use of PVC, or indirectly by using products made from caustic soda, are responsible for vinyl chloride being in rural Ohio. Our appetite for cheap polymer — and crunchy pretzels — is why vinyl chloride was on train 32N.
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Paul J. Heney, the VP, Editorial Director for Design World magazine, has a BS in Engineering Science & Mechanics and minors in Technical Communications and Biomedical Engineering from Georgia Tech. He has written about fluid power, aerospace, robotics, medical, green engineering, and general manufacturing topics for more than 25 years. He has won numerous regional and national awards for his writing from the American Society of Business Publication Editors.
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