This is a continuation of what I talked about last week but focused on polyester resin manufacturing rather than epoxies. And yes, there is quite a bit of history about the toxicity of this chemistry and also good reasons that boat manufacturers have had to move their production indoors and all of the people doing the boat fabrication wear protective clothing with face masks with positive air ventilation. I will talk about all of that in this post as well as some other things.
First, however, I need to start with what makes up a polyester resin. There are three types that are in broad use today, the most prevalent of which is isophthalic polyester. The other two acids that can be used to make a polyester resin are the orthophthalic acid version and the terephthalic acid version. In fact, isophthalic polyester resin commonly starts with terephthalic acid which is converted into isophthalic acid. These resins start with a benzene ring and each has two COOH groups attached to it. The difference between them is where the two COOH groups are attached to the ring. The following graphic shows where the COOH groups are attached in the two most common versions – orthophthalic and isophthalic acids.
The tere- version of this acid, which has the two COOH groups across from each other in the ring, is not used as much as is the iso- version of this acid. This is predominantly because isophthalic acid based polyester resins are less susceptible to degradation when exposed to corrosive environments – like seawater.
So – where do we get all of these phthalic acids? They are all currently made using a refined petroleum feedstock in the form of xylene. This compound is a benzene ring with two methyl groups attached to it and is commonly used as a solvent for paints. Xylene is a close cousin of toluene (only one methyl group) which is on the Prop 65 list which means that it is banned in California. It is also banned in the EU, so toluene is by and large not used any more. Xylene is probably not far behind it because it can also cause all sorts of havoc with the human body, including stopping your heart and causing you to go blind if you get the stuff in your eyes.
All of this of course translates to all of the versions of phthalic acid since they are derived from xylene. It turns out that phthalate esters are used in lots of cosmetic products, nail polish, hairsprays, etc. so you most probably have quite a bit of this stuff in your house or apartment. And when ingested or inhaled, the phthalate esters go into the blood stream, make it to your liver, and the final product that you eliminate is a phthalic acid.
As you can see, we are already into toxicity before we even get started making polyester resins. The rest of the resin, once you have isophthalic acid comes from reaction of this to an organic alcohol, with ethylene glycol (antifreeze) being the most common. This makes the backbone of the resin and what you get from this reaction is what is called an unsaturated resin and water. Finally, to make the resin stable and have a place to cross-link, this resin is most commonly mixed with another compound with a benzene ring – styrene. Making the solid cross-linked thermoset resin that keeps the glass fibers in the boat hull together requires the double bond that is in the styrene. That is also what makes styrene so toxic to humans because the double bonded carbons can wreak havoc in the human body. In the early days of sailboat manufacture in California and the Pacific Northwest (Seattle), there was no control over either exposure to the resin or exposure to the styrene, a lot of which came off as a vapor. So all of the people working down inside of a mold for a Westsail 42 (for instance) in the 1970’s were exposed to high levels of phthalic acids, styrene, and all of the other organic solvents used to make the resin flow easily. A lot of them developed cardiovascular disease, cancers of all varieties, pulmonary diseases and cancers, and all sorts of metabolic disorders. Not many of them survive to this day.
That is just the toxicity side of things associated with polyesters. These plastics are also associated with a good bit of the microplastic pollution that we see in our rivers, lakes, the ocean, and probably in the tap water that you get from your faucet. This is because polyester is the basis for a good bit of the fiber that is woven into your clothing. Polyester makes a very good thread that is quite similar to cotton in that it can be made to have a soft feel, and it will wick moisture away from the body. A lot of athletic clothing as well as a lot of other clothing is made using polyester fabrics. This makes polyester microfibers one of the most ubiquitous microplastics problems that we face today. It is in a slightly different form than polyester resins used for composites since the polyester fabric is actually a thermoplastic (PET – like in soda bottles) rather than a thermoset. It is the tiny little microfibers that come off of these fabrics that are very persistent in the environment much unlike cotton which is completely biodegradable. Polyester is not. Every time you wash your polyester clothes small amounts of polyester microfiber is released into the wastewater stream, which eventually makes it to the rivers, lakes, and the ocean. So, that piece of rockfish you had for lunch or the hamburger you had at McDonalds both have small amounts of polyester microfiber in them. It is in you right now – albeit at a very low level that probably is not necessarily harmful. In other words, polyester microfiber, which is polyethylene terephthalate, is a forever chemical. While it does not have fluorine in the organic compound and is therefore not a PFAS, it is as persistent in the environment as a PFAS.
Another source of polyester microplastics comes from boats that are either abandoned at water’s edge or are ground up and landfilled. This is also true of fiberglass tennis rackets, golf club shafts, old bathtubs and shower surrounds, and all sorts of industrial tanks and structures. Glass fiber reinforced plastics are very long lived, much lighter and more resistant to corrosion than any metals or even wood and are very chemically resistant. So they have been used for storage of all sorts of highly reactive industrial chemistry over the years. When all of these things get abandoned or decommissioned, the fiberglass composite is usually chopped up or ground up and landfilled.
That’s enough bad news for this week. The good news in all of this is that there are now companies that are beginning to be able to make a profit from the recycling of old fiberglass composite parts (wind turbine blades, old boat hulls, etc.). I have talked about these companies here fairly recently. There are a few of them in the EU, with Composite Recycling being the most successful to date. And there are also a couple here in the US that do the same thing – remove the resin from the fiber and end up with a fiber form that can be reused in new fiberglass composites and an oily substance that can be made into new resin. Also, with the new laws in the EU, and some that have been proposed here in the US, manufacturers of wind turbine blades and boat hulls are required to include the cost of recycling of the composite at the end of the useful life of these ubiquitous things made from glass reinforced polyester plastic.
So, again, that light at the end of this tunnel is not an oncoming train. There are solutions that have finally been worked out that have gotten to the point where it is economically viable to reclaim both the fiber and the resin from used or end of life fiberglass parts and pieces.
That’s about it for this week. This is the next installment of this multi-part series on the topic of toxic chemicals, PFAS, and microplastics as a result of the composites industry. Next week I’m going to cover another commonly used resin system – vinyl ester resin – which is sort of a cross between epoxy and polyester. I’ll explain all of that next week.
As always, I hope everyone that reads these posts enjoys them as much as I enjoy writing them. I will post this first on my website – www.nedpatton.com – and then on LinkedIn. And if anyone wants to provide comments to this, I welcome them with open arms. Comments, criticisms, etc. are all quite welcome. I really do want to engage in a conversation with all of you about composites because we can learn so much from each other as long as we share our own perspectives.
My second book is now completely in the hands of my publisher. Most of you know that it is about what I have been writing in these newsletters for the last 6 months or so – sustainability of composites and a path to the future that does not include using fossil fuels for either the raw materials or the process energy to make composites. The title of the book, at least for now, is “Close the Circle, A Roadmap to Composite Materials Sustainability.” It truly is a roadmap which I hope that at least at some level the industry will follow. Only time will tell.
Finally, I still need to plug my first book, so here’s the plug. The book pretty much covers the watershed in composites, starting with a brief history of composites, then introducing the Periodic Table and why Carbon is such an important and interesting element. The book was published and made available last August and is available both on Amazon and from McFarland Books – my publisher. However, the best place to get one is to go to my website and buy one. I will send you a signed copy for the same price you would get charged on Amazon for an unsigned one, except that I have to charge for shipping. Anyway, here’s the link to get your signed copy: https://www.nedpatton.com/product-page/the-string-and-glue-of-our-world-signed-copy. And as usual, here’s a picture of the book.
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