Yes, I’m going to talk a bit more about sustainability of composites here – mostly about some new stuff that I have been reading about lately when it comes to recycling efforts for composites.
And, yes, the efforts to develop recycling processes and to scale them up to commercial size – think in the hundreds of tons range – are actually starting to come to fruition. I know I’ve talked about this in the past and keep coming back to it. I do this because it is the most critical thing happening in composites today, and it is one of the most, if not the most, active research and development efforts going on in composites today. The pic to the right is the title page of an article about 22 companies in the composites recycling business worldwide, focusing on the top 5. These 22 companies are beginning to recycle composites at industrial scale – or are in the midst of scaling up processes that have been proven to work.
To that end, there is a conference being put on later this year by Composites World all about carbon fiber. This conference is in Salt Lake City, and one of the major themes of the conference is sustainability of carbon fiber composites. This runs the gamut from methods to recycle current carbon fiber composites to how to make high performance carbon fibers from plant-based sources, that is, plant-based PolyAcryloNitrile (PAN) the precursor to most of the carbon fibers in use today. While in today’s market PAN comes from petroleum, researchers in large companies have developed a means of creating PAN from plant-based sources. I think I have mentioned that previously, but restating it is a good reminder that this is happening.
And, the genesis of this post is another recent (7/7/2023) article in Composites World about a University in Australia, the University of Sydney, that has developed and proven a much more efficient process for recycling carbon fiber composites than what is being done in the remainder of the industry. A recent paper in ScienceDirect by Y. Wei and S. A. Hadigheh of the U of Sydney (https://www.sciencedirect.com/science/article/pii/S1359836823002895) outlines the process that these researchers have come up with. The pic above is Figure 2 in that paper. It is sort of a mix of a solvolysis pre-treatment to soften up the resin’s chemical bonds, and then a low temperature pyrolysis-like thermal treatment to break the bonds, thus lowering the pyrolysis temperature to the point that they can recover more than 90% of the strength and stiffness of the virgin carbon fiber. And this is good enough for re-use in a new composite application.
As it turns out, the solvolysis pre-treatment of the carbon fiber composite, softening the chemical bonds in the resin matrix, allows reduction in the pyrolysis temperature from 700° to a temperature of 450°C, which does much less damage to the carbon fiber. And, what they also found, because they tried several different acids to their solvolysis process, pre-treating the carbon fiber composite with diluted sulfuric acid at 180°C produced the best results (softening the matrix) than most of the other solvents tried.
This is just one of the latest examples of work that is ongoing in recycling of carbon and glass fiber composites that has the potential to do a more efficient job of reclaiming high performance carbon and glass fibers in their continuous form, and that also one day will have the potential of reclaiming the resin by breaking down the chemical bonds in the resin plastic materials.
This is, however, only one example of what researchers in this field are up to these days. There are, however, several companies that are invested in recycling carbon fiber composites in a big way. This graphic to the right is from the article whose title page is the first pic in this post.
The first one in this graphic is Mallinda – a US startup that has developed a patented resin that is inherently recyclable. Their process apparently uses a reversible chemistry for the resin, and their recycling process manipulates that resin reducing it back to the monomers it was made with. So, this is a complete circle of life recycling method. It unfortunately is not universally applicable because of the patented resin, but it is a large step in the right direction.
The second company is ELG Carbon Fiber – a startup in the UK that is developing and manufacturing large scale composite recycling equipment. And, they have a modular and scalable Hardware-as-a-Service business model, so they can be easily expanded to industrial scale just by adding more units.
Vartega - to the right in this pic, is another US startup and it also developing carbon fiber recycling equipment, using a different process than some others that they claim retains nearly all of the properties of the virgin carbon fiber. Their business model is also modular and scalable, and is a Hardware-as-a-Service, so they can bring the equipment to the site where the carbon fiber composite needs to be recycled.
In Spain, Bcircular is using technology developed by the Spanish National Research Council to recycle both carbon and glass fibers from mostly wind turbine blades. Their end product is apparently high quality carbon and glass fibers with the remainder usable as a source of fuel.
Finally, a Dutch organization – the Thermoplastic Composites Application Center (TPAC) – is collaborating with small and medium sized enterprises, using funding from the Dutch Government, to advance the R&D of recycling techniques for fiber reinforced thermoplastics. TPAC is developing a process that removes the thermoplastic while retaining as much of the mechanical and physical properties as possible of the carbon fiber. This is a much more difficult process than removing the typical thermoset resins from the fibers, since thermoplastics are inherently very resistant to chemical attack, unlike most epoxies.
Well, that’s probably enough for one newsletter. Please remember to take a look at my website, where this newsletter is originally posted. And if you do, please provide your email address, so that you will get early announcements of happenings in composites.
And as always, please take a look at the McFarland Books site for my upcoming book – “The String and Glue of our World”. It is available for pre-sale on the McFarland site, as well as Amazon, Barnes and Nobles, and several other bookseller sites.
And, as always, stay tuned to this newsletter. McFarland says that the book will be out in August, and they have also said that it will come out about two weeks after I see the page proofs. And of course, my readers here will know when that happens because I will announce it here. And, I also plan to start giving out little snippets of the book so that all of you can see how it’s written. Of course, most of you are used to my first person, conversational style, so the book won’t be a total surprise.
See you all next week.
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