MineMan
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Increasing Wood Density
https://www.rt.com/news/418381-bulletproof-wood-stronger-tha...
I know, I know, its from RT....
But does anyone with more chemistry experience want to give this a try? Looks like it could be done in an amateur setting...
I would like to try it, but don't know how to press it while at 100C for several hrs.
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elementcollector1
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Seems like the easiest method would be to stick it in a furnace and put a huge weight on top.
I wonder if any methanol is distilled off during the process?
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Bert
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From some other things I have seen done with wood, I would try immersing it in liquid CO2, pressing it similarly, but cold. Should do pretty much the
same thing. Lignin flows, you can tie a board like a spaghetti noodle.
[Edited on 10-2-2018 by Bert]
[Edited on 10-2-2018 by Bert]
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elementcollector1
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Seems like the paper advocates removal of about 45% of the lignin as part of the procedure.
Would pressing it with more weight than the researchers used lead to a stronger board? I'm wondering how far this apparent strengthening mechanism
will go.
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NedsHead
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Soaking the wood in ammonia followed by pressing might be another way of increasing the density
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j_sum1
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Popsicle sticks, G clamps, oven... Thos is a doable investigation.
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j_sum1
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Mentioned in the abstract -- apparently this new process is denser.
https://www.nature.com/articles/nature25476
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NEMO-Chemistry
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Its laminated, so pressing etc will only get you so far. I bet they used steam and a press, but then again i only just found out the easter bunny isnt
real!
Can you believe that shit! Not real!!
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Vomaturge
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Quote: Originally posted by NEMO-Chemistry  | Its laminated, so pressing etc will only get you so far. I bet they used steam and a press, but then again i only just found out the easter bunny isnt
real!
Can you believe that shit! Not real!! |
I've got doubts too. However, tripling the density and reducing the volume by 5 seems reasonable, depending on the initial wood density. Softwood
weigh about .4-.6 g/cc
https://www.engineeringtoolbox.com/wood-density-d_40.html
Straight cellulose weighs maybe 1.5 g/cc if you believe Wikipedia:
https://en.m.wikipedia.org/wiki/Cellulose
They used a chemical process to remove everything but the cellulose, leaving a very porous structure, and then they compressed it until it had hardly
any openings. They didn't say whether that took 10 MPa, or 10GPa, and whether it was pressed in a vice/press or if it was isostatically pressed (ie,
sealed in a flexible water-tight bag at atmospheric pressure and subjected to high fluid pressure in a tank). I would kind of expect crushing the
hollow pores to weaken wood, but if the cellulose can somehow bond to itself in the compressed form, it might be really strong, like they say. But no
guarantees. I suspect they made a few of these sheets (if they really did make them) and laminated them after pressing them separately.
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NedsHead
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Smells like fake news, the YouTube video linked in the article has comments disabled, rating disabled and is unlisted
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j_sum1
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Not quite correct Vomaturge.
| Quote: | | process involves the partial removal of lignin and hemicellulose from the natural wood |
and | Quote: | | complete densification of the natural wood with highly aligned cellulose nanofibres |
from the abstract I cited above.
It would seem that there is some new bonding formed between the cellulose nanofibres but that some lignin is still required.
The purpose of the pressure seems to collapse the voids that remain once the lignin is gone and also to facilitate bonding between the remaining
cellulose. For this I would not assume that the required pressure needs be that high.
One of the links I viewed showed a video of a ballistics test. The discovery looks legit and the result of some genuine science.
What we don't know (until some one with access looks at the original paper) is the composition of the NaOH/Na2SO3 boiling solution and the conditions
of the pressure heating processes. Nor do we know if this process requires structurally sound timber to begin with in order to take advantage of the
already present microstructure, or whether it could equally be performed with sawdust or wood pulp.
I am picking that the process exploits structures already present in the wood. Hints in this direction are references to alignment of the cellulose
(which makes good sense) and also the fact that they felt it necessary to test an (unspecified) number of wood types. I would not expect all woods to
be equal under this process.
[edit]
@NedsHead
This is not the kind of thing one normally finds with fake news. Nature is fairly prestigious AFAIK. It has had some time for review.
[Edited on 11-2-2018 by j_sum1]
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Bert
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A long time ago, I wanted to bend wood. Steaming it worked, but needed green wood with the grain pretty much perfectly in line with the long axis of
the piece and perpendicular to the desired curve- or SNAP!!!. You picked your tree, and split out your work pieces VERY carefully, then you could mill
the promising looking ones a bit for square, flat or whatever cross section was needed. Lots of waste. Then more waste from the ones that busted
anyhow. Plus lots of minor burns, sweat and irritation.
Ammonia would have worked, but needed substantial infrastructure to keep from killing yourself, plus the whole anhydrous ammonia availability vs. meth
cooks prevalence for a non industrial user.
Thank God for beer drinkers, you can get liquid CO2 just about anywheres and if you can avoid frost bite or asphyxiation, it's not as bad as
ammonia...
Apparently, it's good for not only mobilising the lignin, but for OXIDIZING it and generating some tasty byproducts? Never knew back then.
Attachment: Supercritical CO2 Oxidation of Lignin.pdf (331kB)
This file has been downloaded 284 times
(Uhhhh... Is it wrong that I'm wondering what the black powder from collapsed cellulosic structures, lignin depleted wood charcoal is like?)
[Edited on 11-2-2018 by Bert]
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SWIM
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This kinda reminds me of how they make Vycor.
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Vomaturge
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When I said that the pressure could be 10 GPa, I really only meant that it was unspecified, and could be any arbitrary amount. This, together with a
comparison of the density of raw wood and pure cellulose (without any air gaps or porosity) shows that they may indeed have tripled the density of
some low-density wood. Good eye, j_sum 1, finding the detail about residual lignin holding the material together after compression. I overlooked that
part, but found it after you mentioned it. This detail lends credibility that the material would increase in strength after pressing, as opposed to
decrease due to a broken internal structure. It also would be a crucial concept for anyone trying to replicate the results. For instance, it suggests
that the pressure should be maintained while the wood cools, and that a more effective lignin removal process may actually produce a weaker final
product.
So far:
A back of the envelope calculation suggests that wood's density can be tripled, by a combination of chemical and mechanical treatments.
The paper gives a plausible explanation for this material's reported strength.
The paper was in a reputable journal.
Everything seems pretty legit.
All the raw materials are readily available, and the process seems within reach of the amateur experimenter, unless the "pressing" stage requires very
extreme pressures or a combination of difficult conditions. Even low pressure compaction would probably limit the home experimenter to a small-scale,
proof of concept test.
Finding the exact composition for the sodium sulfite/hydroxide solution and press conditions might be possible via trial and error, but it would be
quicker and more reliable to get these parameters from the original experiment.
[Edited on 11-2-2018 by Vomaturge]
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elementcollector1
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What I'm still wondering (aside from the detailed specifics about this procedure, can anyone get a copy of the full paper?) is how this could
actually be used for body armor. Could one carve an armor piece out of wood, fill in the interior with some incompressible material, and then put the
whole thing under pressure somehow? Or would individual flat plates have to be made and strung together into a piece of armor?
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j_sum1
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I am not sure that anyone has got to specifics of applications yet -- aside from seeing possibiities. This is early days for an emerging technology.
If we are talking body armour then I envisage a moulded panel -- similar perhaps in appearance to the back of a violin. This panel then gets sewn into
a kevlar (or more likely nomex) vest. Of course this application requires more than just the ability to stop a bullet: it must be designed such that
the energy of the bullet is dissipated. So who knows how the final product might look.
The attraction for me is the apparent simplicity and seeming versitility. Wooden car panels perhaps? There's a green tech that I have not heard for a
while.
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Bert
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Ballistic armor is typically NOT done like medievil plate or scale armor, or WWII tank armor. It is usually done with a mat of high strength fiber and
a hard, stiff trauma plate.
This densified wood substance might do for a plate behind Kevlar or Spectra, but any ammount you could carry in a complete upper body encasing armor
shell? I am willing to bet I can put a projectile through. Don't think it would be hard enough for an outer layer to start the breakup of a full metal
jacket or monometal projectile either.
[Edited on 11-2-2018 by Bert]
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aga
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A "high strength fibre" like cellulose maybe ?
You got a gun. Go shoot a tree and see how far thru it gets. Not very far is my prediction.
Sciencyfying it for news is all that happened there.
The Water content helps a lot.
Edit:
If you actually Do that, please tell what the propellant size/grains are, also the slug weight, distance and temperature, then the penetration depth.
Kinda science-like.
[Edited on 11-2-2018 by aga]
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Bert
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If you have not had an idle young adult life of shooting "stuff" with guns to see for yourself what happens, go here:
The Original Box 'O Truth
A .45 acp 240 gr. FMJ easily goes through 6" of pine. A .22lr plain Lead bullet out of a rifle almost as much. These are SLOW, reatively LOW ENERGY
rounds.
A 7.62 NATO round with a full metal jacket 150 gr. projectile moving around 2600 fps can go through a 16" of a tree trunk, in my personal experience.
BOY, was my mom ever pissed.
Body armor has to do some combination of breaking up a projectile, slowing projectiles or fragments down and finally, spreading the impact force out
over a wider area. The dense wood could be a substitute for some of the stiff but not HARD elements.
Wood is the ORIGINAL high strength/low weight composite material...
I respect cellulose capabilities a great deal. Some of my favorite structures are made with trees as the primary ingredient, particularly boats-
Stiffer than resin and fiber glass per volume and stronger than steel, weight per weight if you know which wood and how to use it. Monocoque
construction from cold moulded veneers laid at angles rather than traditional planking. Sure, you can do better with Carbon fiber now, but have you
ever compared being covered with sawdust to chopped glass, kevlar or carbon fibers for how your skin feels at the end of the day?
If these guys can engineer a modified wood better than I, I will happily adopt it.
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MineMan
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Ok Gals and Gents. This looked like a good material science experiment that could be done at home, my chemistry is rough, so I love all of the
responses. I am in a hotel room, so this one will have to wait, but if it is as good as promised I would like to maybe even suspend it in PETG and
try printing with it....
Glad we had an awesome discussion.
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