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  • Writer's pictureNed Patton

Sustainability and Composite Resins


I’m back at sustainability of composites again, but this week I want to talk about the glue part – resins. Again, there are at least two camps here – those that make their resins from sustainable feedstocks – mostly plants; and those that make their resins so that they can be decomposed more easily, allowing the string and glue to be separated and reused.


The windmill pic comes from a website in the U.K. (https://www.uk-cpi.com/materials/sustainable-composites) where they are formulating new resin systems using sap primarily from trees. CPI (Centre for Process Innovation Limited) is an organization that has laboratories, scientists, chemists, and others and is basically a research lab / think tank. They are partnering with the UK’s National Composites Center to formulate recyclable and reusable resins using their laboratories and their expertise. They started with the development of reusable, recyclable, and compostable plastic alternatives primarily for packaging, and have recently branched out in to recyclable, reusable composite resins.

There is a good example of reuse and recyclability of resins in the pic to the right. What you see are the parts that are made using “reprocessable, repairable, and recyclable” epoxies and carbon fiber. The pic is from an article in Composites World from 5/24/2021, where they talk about an organization in Spain (CIDETEC - https://surfaceengineering.cidetec.es/en/home) that has developed an epoxy that has a pair of disulfide groups that make the thermoset epoxy act like a thermoset at temperatures below the “glass transition temperature” and a thermoplastic above this temperature. That means that this resin can be reprocessed using heat, and it can also be removed from the carbon fiber that it is stuck to and reused. This is sort of the ultimate in recyclability and sustainability of resin systems, which is why I decided to showcase this organization in this post.


CIDETEC new leads 11 partners in the Horizon 2020 project named AIRPOXY that is maturing this technology from a Technology Readiness Level (TRL) of 3 to 5. If you are wondering what a TRL level is, please visit: https://en.wikipedia.org/wiki/Technology_readiness_level. Originally developed by NASA, this is the scale by which engineers gauge where they are on the development path toward commercialization. I, of course, am quite well aware of TRL levels, since I’ve been spending most of my career pushing technologies from TRL 2 or 3 to TRL 7.


The other camp that I talked about at the outset of this post is the camp that is making their resins (glues) from the naturally occurring glue-like resins derived from plants. This is of course something like taking the sap from a tree and using it as a glue as was done in ancient times. In today’s world, there are several plants that have compounds that are rather simple to extract and also rather simple to convert into a resin system that is applicable to composites. That’s where the windmill picture and the sailboat picture come in to play in the pic at the head of this post.


The sailboat pic to the right is from a French organization by the name of SICOMIN that has developed a Greenpoxy® bio-based epoxy resin system. This resin was used on the Greenboats® Flax 27, and entirely bio-based composite sailboat. Their InfuGreen 810 low viscosity plant-based epoxy was vacuum infused into a flax fiber laid up mold to make the hull, deck, and all of the internal bulkheads and stiffeners of this beautiful, classic design daysailer. And, their resin systems carries the DNV-GL approval seal, which means that this resin system is ready for prime time.


That’s about enough for this post. As you can see, I am keenly interested in the sustainability of composites and moving the industry off of the use of petroleum as a feedstock. It’s time to do this now because composites are our future, and our future is not petroleum – it’s what we can grow, harvest, and turn into usable products for humanity. Unfortunately, most of the basic research that is being done in this space is in Europe. The US has not caught up with the sustainability movement that is ongoing in the composites industry, and to be quite frank about it, the US lags behind in all aspects of sustainability.


It’s about time we caught up – don’t you think.

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