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New plant-derived composite is tough as bone and hard as aluminum
- vorticalbox 5y agoWhat is the difference between "tough" and "hard"? I would use these terms interchangeably.
- lordnacho 5y agoHard : doesn't deform easily Tough: doesn't break easily So a pane of glass is hard but not tough. Lump of clay is tough but not hard.
- pvg 5y agoThere's quite a maze of twisty definitions of these, all slightly different, both in applied and theoretical flavours: https://en.wikipedia.org/wiki/Hardness https://en.wikipedia.org/wiki/Hardness (warning: clickholes)
- Etheryte 5y agoToughness is how much energy something can take without breaking, e.g. the more weight you can put on a tabletop before it breaks in half, the tougher it is. The opposite of tough is brittle, if that makes more sense. Hardness is how much energy something can take without deforming, e.g. playdoh is not hard.
- dieselerator 5y agoI guessed this might be buckthorn, but no cellulose nanocrystals (CNC) from the article: "At the nanoscale, CNCs are stronger and stiffer than Kevlar. If the crystals could be worked into materials in significant fractions, CNCs could be a route to stronger, more sustainable, naturally derived plastics." the original paper: Printable, castable, nanocrystalline cellulose-epoxy composites exhibiting hierarchical nacre-like toughening <https://link.springer.com/article/10.1007/s10570-021-04384-7 https://link.springer.com/article/10.1007/s10570-021-04384-7> (paywall)
- marsven_422 5y ago
- CrazyPyroLinux 5y agoSo it's FDM printable? Side note: I can see the overloading of "CNC" being confusing ;)
- gtsop 5y agoTwo concerns, if anyone can answer: 1. Does it look like the production process can scale big enough? 2. Would that mean even more incentive to chop down trees?
- ummonk 5y agoThe answer to question 1 for these sorts of articles is nearly always "no".
- dataflow 5y ago> 2. Would that mean even more incentive to chop down trees? That might actually be a good thing - trees absorb carbon, which we need to do, quickly. We just need to make sure to plant new ones in their place.
- MobiusHorizons 5y agoInterestingly the article switches back and forth between “hard as bone, tough as aluminum” and “hard as aluminum tough as bone” Neither aluminum nor bone are very hard on the mohs or Rockwell scales though, so I assume toughness is the main desirable attribute.
- ummonk 5y agoFrom some quick Googling (no, I don't know the hardness of bone off the top of my head though having worked with it I can say it's quite soft just like aluminum), it looks like aluminum and bone aren't that different in hardness or toughness, with aluminum alloy being somewhat harder and tougher at the expense of higher density.
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- olliej 5y agoOk, so this sounds like a cellulose/resin composite (compare to carbon fibre). Based on https://link.springer.com/article/10.1007/s10570-021-04384-7 https://link.springer.com/article/10.1007/s10570-021-04384-7 (the summary of the source article), it is substantially weaker than carbon fibre. Fracture toughness is afaict ~50MPa^1/2 vs 5.2. The article reports hardness of 0.66GPa, but from the summary I don't know by which modulus, however carbon fibre is stronger than that in all measures.
- ksec 5y ago>“We basically deconstructed wood, and reconstructed it,” Rao says. “We took the best components of wood, which is cellulose nanocrystals, and reconstructed them to achieve a new composite material.” Potential for Construction material? As with all these discover my question is always how do we get it to scale and extremely affordable.
- bestouff 5y ago... and preferably pollute less than using wood in the first place.
- ThalesX 5y agoIs wood considered a polutant when not burnt?
- Aromasin 5y agoNo, it is (largely, machinery aside) carbon neutral - provided we're growing said wood on existing forestry reserves or farmland, not wildland or old-growth forest.
- eptcyka 5y agoUnless treated, it doesn't matter if wood is burned or left to decay as it will release the same amount of CO2 in the atmosphere anyway.
- cassepipe 5y agoWell there's a time component to burning or leaving to decay. Leaving a tree to decay takes a long time and there's time for many other trees to grow in the meantime. Pretty safe.
- eptcyka 5y agoIn mature forests, the replacement time is pretty much 1:1. If you disregard the nutrients being taken away from the soil and the energy needed to transport and dry the wood, wood would be a pretty good fuel. Slightly worse than nuclear, I imagine.
- ginko 5y agoIs bone particularly tough though? I would have guessed some of the harder woods would already surpass or at least match it.
- hgomersall 5y agoThere was a standing joke during engineering undergrad that wood-along-the-grain always came out best on all the material selection charts. Essentially the answer to all questions about what material to use was "wood along the grain". I suspect that wood genuinely is close to being that good and its consistency (and the tricky across-the-grain bit) is what stops it being used everywhere.
- thaumasiotes 5y agoWood is also more of a fire risk than other materials.
- dmos62 5y agoThis comes up when talking about the wooden skyscrapers being built. Maybe someone can elaborate, but, as far as I've heard, treated construction wood has pretty good fire-damage characteristics.
- Aromasin 5y agoWood is at the same time a combustible and fire-safe material. The required fire resistance of wood structures can be achieved by adding to the size of the structure, adding a protective cladding, using a non-combustible insulation material, or by improving the fire resistance of the wood structure with a fire-retardant treatment.
- _0w8t 5y agoSteel and iron are also combustible even if that requires a high temperature. During bombing of Dresden in WWII that contributed to massive sustained fires.
- TedShiller 5y agoIt sounds cool, but then this: > a composite made mostly from cellulose nanocrystals mixed with a bit of synthetic polymer So it still contains non-degradable plastic, just less plastic than before. There have been a spate of such articles recently, where "less plastic" is pitched as "no plastic". I'm not saying it's bad, but it's not as good as it appears.
- ainiriand 5y agoThe subtitle effectively says 'new plastics'. I don't think it is trying to pitch 'no plastic'.
- ehnto 5y agoWe don't know which polymer it is, nor how or what it's synthesized from. PLA is synthesized for example, just not from petrochemicals.
- willcipriano 5y agoBeing non-biodegradable is a pretty important feature for anything that has to interact with the elements. A house constructed out of truly biodegradable materials would be a disaster.
- kibwen 5y agoWell, FSVO "disaster". Wood is biodegradable, and a house made entirely out of wood (say a log cabin) might last only 50 years, but that's plenty of time on human scales of habitability.
- throwaway17_17 5y agoIn actual, no context terms I agree that a home Meade from wood doesn’t biodegrade fast enough on human scales. However, Infeel like the externals associated with the cultural concepts, particular in ‘the west’, around real property and houses as investments (either for rent or for future descendents) make this statement not accurate in a practical way. So, I don’t think it stands as an argument against excluding non-biodegradable materials in construction projects.
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- ramesh31 5y agoSo they've invented... MDF?
- polymerist 5y agoCellulose nanocrystals (CNCs) have been around for awhile now just like how we have had carbon nanotubes (CNTs) and graphene. These nanoparticles offer really a interesting strength to weight ratio and a relatively easily modified surface compared to CNTs. The article posted here is misleading due to the relatively high cost of the CNCs to isolate and then use in what looks to be an under cured epoxy resin. Isolating the CNCs potentially can be done through mechanical means, but I suspect the authors here were using chemical isolation through some sort of acid hydrolysis (they don't say in the abstract). But overall mixing the CNCs at that weight ratio with an epoxy resin should have yielded 1-3 GPa modulus or higher and the fact that they got 0.66 to me indicates it's under cured and not really that useful. I actually worked on this stuff when I was in graduate school and we were doing surface modified CNCs with a biobased epoxy resin. We loaded at 1-10 wt% of CNCs and got modulus values between 2-3 GPa with some modest increases in Tg. We were expecting better results, but that's life. This to me seems like MIT is trying to toot their own horn for some not very interesting results.
- jker 5y agoThis and similar breakthroughs are truly thrilling to read about. They’re demonstrations that human ingenuity is being applied to combat climate change - and there are few forces on earth more formidable than human ingenuity. The fight is on, and we can win. (True, human ingenuity got us into this mess in the first place.) All that being said, it’s often worth reading these kinds of articles from the bottom up so as to avoid disappointment. I scrolled to the end first and found this: “While shrinkage isn’t much of a problem when printing small objects, anything bigger could buckle or crack as the composite dries.” They may solve this too, but it’s not time to celebrate just yet.