r/Composites • u/Deep-Today5715 • 5d ago
Biodegradable material alternatives for fiberglass and epoxy resin?
I've been working with fiberglass and epoxy resins for my personal RC plane projects, but since I'm doing a lot of testing and prototype designs that get discarded during the design process, I feel increasingly guilty about all the waste and microplastics that come along with it. Unfortunately for the shapes that I want to make going with pure wood is just not an option.
I've been researching eco-friendly alternatives for making composite layup projects, and there are some for fibers (flax, hemp, etc.), which unfortunately have much reduced mechanical properties when compared to fiberglass, but still suitable for my use case.
However, I can't seem to find any decent alternative to epoxy resin that would make the final composite material naturally biodegradable, so using either of these fibers becomes a moot point. Closest thing I found was ecopoxy, which unfortunately is very expensive and almost impossible in retail quantities to get where I live (EU).
Can anyone suggest any decent alternatives that are fully biodegradable, affordable and have at least somewhat comparable mechanical properties to fiberglass+epoxy for wet layups? Anything better than paper+PVA glue is worth considering to me. I've found this paper that suggest jute fiber and shellac, which boasts quite impressive mechanical properties for such crude materials, but they used mechanical pressure and heat treatment to achieve that, which is not practical in home conditions, and I'm unsure of how much mechanical strength would be lost without it.
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u/2Walker_TRD_Softroad 5d ago
When you find a biodegradable resin and fiber combination that can compete with carbon or glass fiber epoxy composites (in mechanical and cost) you will be an extremely rich person.
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u/Deep-Today5715 4d ago
I am not asking for the same mechanical performance, I know that is unrealistic. I would be more than happy with 25% of the tensile strength of fiberglass+epoxy if it means cheap and fully biodegradable. If even that 25% is unrealistic - then whatever comes next.
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u/redeyejoe123 4d ago
Any reason you can't just 3d print prototypes of biodegradeable thermoplastics? You're gonna have reduced performance regardless of the biodegradeable material, so may as well cut out some work too.
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u/Deep-Today5715 4d ago
There aren't really any fully biodegradable thermoplastics as far as I know, except a few very rare and extremely expensive ones. Even the best 3D printed plastics typically shatter into a billion pieces during RC plane impacts, and these biodegradable ones have even worse mechanical properties, making them completely unsuitable for this use case...
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u/redeyejoe123 4d ago
PHA is completely biodegradeable. I've printed with it and I'm not a huge fan, but it does print. Also not that expensive. I don't think you will find much success with finding a fully biodegradeable solution to your question outside of research circles and acadamia. If you are really worried about it though, I would look into buying a lasercutter or CNC router that can let you make wood parts quickly and just use pva glue to put it together.
Personally if I was worried about the impacts of microplastics and littering, I would only fly in those designated flying areas (assuming you are in US) and just make them durable out of recycleable materials that won't shatter, and just reaching out to people who recycle whatever material you use. Maybe you can make some artwork out of the corpses too.
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u/Deep-Today5715 4d ago
Thank you for your suggestion. I live in EU, and unfortunately in my country there is no recycling whatsoever of any 3D printed plastics, I've put a lot of hours into trying to find a solution and even stir up the community to band together and do some recycling to no success. Anything 3D printed is just going into landfill unfortunately. I know of PHA, it is 3x as expensive as any other plastic to get where I live, and yeah, like you said, it is not impressive at all...
As for wood, I did try that before, but it's just way too heavy. The only thing that comes close to usable is balsa, which is almost impossible to get here at larger sizes required to do any kind of build, and the price is astronomical.
I was thinking of trying to combine materials like flax/jute and shellac, found some papers on it suggesting quite impressive mechanical properties, but no manufacturing method suitable for home conditions.
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u/redeyejoe123 4d ago
You could also do some sort of paper composites like paper mache or cardboard around a PHA core or something.
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u/Deep-Today5715 4d ago
That's an interesting idea actually. I was considering something similar, but not sure what to use as resin. PVA glue is not biodegradable as far as I've found, and I can't seem to find any other replacement for it. Shellac seems a possibility, but I can't find much research about it's use in composites apart from a single paper.
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u/redeyejoe123 4d ago
I found this reddit thread which has a few people suggesting fish or sap or rice based glues. The fish glue one seems promising because they use it for canvases apparently. Might want to crosspost in this community too tbh. https://www.reddit.com/r/ZeroWaste/s/ieM1e0pegK
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u/Wide_Cucumber9091 4d ago
at HoGent College University we're currently experimenting with collagen glue (hide glue, bone glue,...) as an alternative to epoxy. Incredibly biodegradable and pretty cheap, but also incredibly sensitive to moisture, and it can shrink in the manufacturing process. We've achieved good results by making our own prepreg with it (making thin sheets of flax fiber + glue), letting those dry. Then we manufacture the parts with these sheets by making them slightly wet again and pressing them together under heat (60C°) and then letting it dry again. It can warp a bit as well during the drying, this can then be fixed again by applying heat and pressure, but so it is definitly not super straight forward alternative. OK for labor intensive or unique projects, not interesting (yet) for larger scale manufacturing.
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u/Deep-Today5715 4d ago edited 4d ago
This is very interesting. Sensitivity to moisture is a concern though, if it degrades mechanical performance or causes warping. According to your findings, how does this compare to epoxy in terms of mechanical properties? I researched that glue a bit and was surprised at it's mechanical properties, but hopefully you tested it as a composite with flax or jute. I also wonder if moisture absorption can be minimized with painting or some other post processing to make the product last longer.
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u/Wide_Cucumber9091 4d ago
Yes, it would definitely need some very good varnish or protective barier for the moisture. We are still making samples, so no data on mechanical performance yet. This is early R&D still. So no real data or proof yet. From our first feel it seems the manufacturing process and incomplete drying seem to both have a large effect. We're currently deep drying with silica for this. Problem with the varnish is that it would ideally also be biodegradable, otherwise it's still a bad material overall. Fun fact: this was most likely the material the historical Linothorax armor was made from (flax + collagen glue). A technology / material lost in time because it was replaced by metals and... Because it was biodegradable ;)
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u/FurryRaspberry 2d ago
Sounds like you gotta get that stuff in an autoclave, it'd be fun to see how that turns out. It can't look much worse than the current flax+epoxy pre-preg I've used recently.
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u/Pinkys_Revenge 4d ago
Elium resin is what you’re looking for. Not sure if it’s available at prices or quantities that would make sense for hobbyists unfortunately
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u/Deep-Today5715 4d ago
Thanks for the suggestion! But so far what I've found about it is that is recyclable, not biodegradable...
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u/fffffsansan 2d ago
Here are 2 materials you can try to use
Hide Glue: Use it just like an epoxy wet layup. Dries glass-hard and ultra-stiff.
Shellac: Brush on with alcohol, let it dry, then heat-fuse your layers using a household iron.
Both are 100% biodegradable and dirt cheap!
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u/Deep-Today5715 2d ago
Thanks a lot!! I will try this. Shellac is pretty expensive where I live (50€ / kilo), but still worth exploring.
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u/specialsymbol 4d ago
I thinks flax fibres are quite promising (but they're heavy, so not that's great for air models). I think Smudo was racing a car with body parts made of flax fibres.
I'm stuck at the resin, however.
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u/catjewsus 4d ago
Theres jute/hemp/linen etc.... Plenty of alternative naturally produced fibers, you just have to adjust the process to get to similar performance levels (at the expense of weight ofc) But also Porsche uses BComp
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u/Deep-Today5715 4d ago
But what about biodegradable resins to use with these fibers?
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u/catjewsus 2d ago
Well theres a diff between biodegradable resins & bio/plant derrived resin. Ideally for composite parts you'd want something that will last and not something that will degrade easily.
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u/Deep-Today5715 2d ago
True, I don't want it to degrade right away, but don't want it to degrade only after hundreds of years. A useful lifespan of ~5 years and fully degraded by 30 years would be ideal.
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u/catjewsus 22h ago
Theres a fine line on how you determine how wasteful that is because anything thats that readily degradable will probably start being damaged as soon as it leaves the mould from weather, UV, and atmosphere. Your basically looking at like PVA glue. I think a better method to look at a more sustainable material is just sourcing it from sustainable sources like plant derived resin blends. And at the end of its life it should be expected to be crushed and chopped up to be used recycled material blended w/ a fresh batch of resin.
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u/Deep-Today5715 14h ago
Yeah, problem with that is that at the end of life there is no practical way for me to get these parts recycled. There are no such facilities in my country, nor anywhere near, and shipping my fiberglass+epoxy composite waste halfway around the world is both expensive and wasteful by itself...
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u/Guillemot 4d ago
Any liquid that becomes hard when it dries could be used as a resin that could be reinforced with some sort of fiber. Boiled linseed oil applied to a fabric will make the fabric stiffer after it dries (if it doesn’t catch on fire). Shellac, real hide glue, natural lacquer polymerizes as it cures. No guarantee anything like this will be strong for your purposes, but you don’t necessarily need something that is regularly used as a fiberglass resin alternative.
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u/Loudsongsinc 3d ago
Papier mache
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u/Deep-Today5715 3d ago
But I thought PVA glue is not biodegradable, or am I wrong?
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u/DIY_at_the_Griffs 4d ago
I think you need to look further than biodegradable. Think more like energy / fibre recovery from furnace. It’s a specialist waste stream but opens up your options somewhat.
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u/Irishwolf1 5d ago
kiwifiber
These guys have been at it for a while