Fully Plant-Based Epoxy Resins - Are They Going Commercial?
- Ned Patton
- Jun 2
- 6 min read
One of the things that I wrote about in the book that I have coming out is the development of fully plant-based epoxies. One article from Molecules that I mention in the book (https://www.mdpi.com/1420-3049/25/5/1158) is from some researchers in Belgium and The Netherlands who developed a resin system from lignocellulosic biomass and plant oils that has the potential to compete directly with aerospace epoxy resins.
So, as I was looking through the text of the book for ideas, this one sprung out at me because I haven’t delved into this subject for about a year, even though this resin and others like it have been in development in research labs both in universities as well as some of the more progressive resin suppliers. A lot of people and companies in this industry have taken on the challenge of reducing the carbon footprint of the industry and sourcing the raw materials from our biological world rather than from the oil and gas industry. This is of course more true in Europe than here because of the environmental regulations enacted across Europe.
As I looked more into this subject, and the use of lignin as the aromatic glue part of the resin, I came across another paper from largely the same researchers. This one was from 2019 and for this system the same group, with the addition of Martijn Wiekamp, and also from Belgium and The Netherlands used a depolymerized lignin as the binding agent and glycerol which is a byproduct of the oil refining process to make a diglycidyl epoxy resin with properties similar to the standard aerospace epoxies made using bisphenol-A as a backbone. What they did find with these experiments is that the higher the lignin content, the stiffer and stronger the resin was. This is probably what led them to try their fully bio-based epoxy using the same lignin but rather than the petroleum byproduct glycerol, using plant-based oils to make the resin. As it turns out, these plant-based oils are replete with aromatic rings (6-carbon benzene rings), making lignin a very good binder for these resins.
All of this work was reported in 2020, and since that time a few others have also reported on their work making epoxy resins from plant oils, lignin, and even things like epoxidized vegetable oils. There is one I found from 2022 where the researchers used epoxidized linseed oil and tannic acid to form an epoxy resin with mechanical properties close to current aerospace grade bisphenol-A based epoxies (https://onlinelibrary.wiley.com/doi/full/10.1002/mame.202200455). They focused not only on the backbone of the resin, but also the means of producing a plant-based hardener similar in behavior to epichlorohydrin. Linseed oil gave them the right backbone with a higher number of cross-linking sites than most other epoxidized plant oils, and tannic acid, since it is a much shorter chain organic acid with lots of phenolic (aromatic or benzene) rings, also had more spots to facilitate the cross-link chemistry. The tannic acid they expected would be a good substitute for epichlorohydrin as a curing agent for the epoxidized linseed oil.
The resin they developed had properties typical of current aerospace grade epoxies both in strength and strain to failure and also exhibited a somewhat lower temperature cure and more complete curing at the lower temperatures that the resins were exposed to. And they did all of this without having to resort to the use of any known toxic chemistries, and even chose plant oils that have been known to be generally safe to use.
To get back to lignin as an epoxy backbone, there is another study I found from 2017 (https://pubs.rsc.org/en/content/articlelanding/2017/ra/c6ra27283e) where the researchers used vanillin that was derived from lignin as a backbone for their plant-based epoxy. To turn the vanillin into something similar in structure to BPA, they used calcium nitrate as an inorganic accelerator to bond two vanillin molecules together to make a bi-phenolic compound very similar to BPA only with an additional functional group in the middle between the two phenolic rings.
But some of you are asking the question – when will these things be available for me to buy, or which ones are on the market today? I have talked quite a bit about Entropy Resins, now part of the West System family of Gudgeon Brothers epoxies. These are largely mixes of plant-based with petroleum based epoxies. Greenpoxy is another of these that range between about 28 to more than 50% plant-based resin in their epoxy resin formulations. Another one that is a fairly recent addition to this space is Super Resin from Japan. These folks are using glycol lignin from Japanese cedars mixed with traditional epoxies to make a laminating resin that is largely bio-based and still maintains the mechanical properties of an aerospace grade laminating resin.
There is one that I did find that is commercially available. This pic is of a traditional two part epoxy, only it is not BPA based, it is made using the hulls of cashews. So here is a company that is taking what would otherwise be a waste product that goes into a landfill and they are making a high value added structural material with it. This is the very definition of a sustainable resin system. While this particular resin system is more suitable for the marine industry than the high performance aerospace industry, that is actually where most of the tonnage of these sorts of resins are going to be used – the marine and wind energy industries. And the market they are targeting is extremely cost and price sensitive, so if they can make it in this market, they have a very good chance of overtaking the petroleum based mid-priced part of the epoxy resin industry. And who doesn’t like cashews (except for those that are allergic of course). To add to this good news story, cashews come from the part of the world that is underdeveloped, like the Ivory Coast and Nigeria in Africa, Vietnam, Cambodia and much of Southeast Asia, Northern Brazil, and other tropical rainforest areas. Hopefully development and cashew plantations won’t overtake the rainforests in those areas, but if the people that grow these nuts for human consumption have another high value added product that they can deliver to one of the fastest growing high technological level industries on the planet, that sounds like a win to me.
That’s about it for this 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. And that is especially true of the companies and research institutions that I mention in these posts. The more we communicate the message the better we will be able to effect the changes in the industry that are needed.
And just to remind everyone, my second book, which should be out in the fall, is a roadmap to a circular and sustainable business model for the industry which I hope that at least at some level the industry will follow. Only time will tell. Since my publisher and I have finally come to agreement about the title for my next book, our daughter has been kind enough to put together a draft of the cover of the book for them to use to come up with a final version. So, I’ve included the approved cover at the end of this post as promised. Let me know whether or not you like the cover. Hopefully people will like it enough and will be interested enough in composites sustainability that they will buy it. And of course I hope that they read it and get engaged. We need all the help we can get.
Last but not least, 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 are pictures of the covers of both books.
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