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A Chemical Bath and a Hot-press Can Transform Wood Into a Material That is Stronger Than Steel, Researchers Find (nature.com) 251

The process, and others like it, could make the humble material an eco-friendly alternative to using plastics and metals in the manufacture of cars and buildings, Nature reported this week. From the report: "It's a new class of materials with great potential," says Li Teng, a mechanics specialist at the University of Maryland in College Park and a co-author of the study published on 7 February in Nature. Attempts to strengthen wood go back decades. Some efforts have focused on synthesizing new materials by extracting the nanofibres in cellulose -- the hard natural polymer in the tubular cells that funnel water through plant tissue. Li's team took a different approach: the researchers focused on modifying the porous structure of natural wood. First, they boiled different wood types, including oak, in a solution of sodium hydroxide and sodium sulfite for seven hours. That treatment left the starchy cellulose mostly intact, but created more hollow space in the wood structure by removing some of the surrounding compounds. These included lignin, a polymer that binds the cellulose. Then the team pressed the block -- like a panini sandwich -- at 100C (212F) for a day. The result: a wooden plank one-fifth the thickness, but three times the density of natural wood -- and 11.5 times stronger. Previous attempts to densify wood have improved the strength by a factor of about three to four.
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A Chemical Bath and a Hot-press Can Transform Wood Into a Material That is Stronger Than Steel, Researchers Find

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  • This oughta make something awesome possible. From enclosures to cones. I'm betting this stuff is hell on a skilsaw.....

    • From the summary:

      The process, and others like it, could make the humble material an eco-friendly alternative to using plastics and metals in the manufacture of cars and buildings, Nature reported this week. From the report:

      There's a reason that we don't build cars and buildings (and other things that need flex) from brittle substances.

  • Science News (Score:5, Informative)

    by Jodka ( 520060 ) on Sunday February 11, 2018 @08:53PM (#56105923)

    There is also a summary here [sciencenews.org] at Sciences News.

  • by Hadlock ( 143607 ) on Sunday February 11, 2018 @09:07PM (#56105965) Homepage Journal

    Generally solid wood is a good choice for many projects due to three key reasons:

    1. Cost

    2. Workability; can be worked with hand tools and power tools, glues easily and strong

    3. Water safe for years with no significant prep work

    Steel is a lot stronger per pound, but to join it you either need to use mechanical fasteners or weld it. This requires expensive ($300+) specialized equipment like a welder and/or drill press. Wooden boats are generally good from 15-20 years without major renovations, and are serviceable with major repairs every 10-15 years up to 60-75 years after initial construction. Steel needs to be galvanized, or painted, or sanded and resurfaced every 2-5 years, especially in a saltwater environment (most of the things in your house arrived from asia in a big steel boat).
     
    Super dense wood that's lost most of it's lignin likely is hyper brittle and doesn't machine well. Also, I can only imagine what happens when it's immersed in water. There's a non-zero chance it swells up like a dry sponge when it comes in contact with water or even regular humidity.

    • by ColdWetDog ( 752185 ) on Sunday February 11, 2018 @09:14PM (#56105983) Homepage

      I'd also wonder how 'eco friendly' this is. Heated sodium hydroxide baths followed by pressure and more heat. Lots of extra joules and eco unfriendly chemicals in there. I suppose it could be recycled easily but so can steel and aluminum.

      • The wood is just heated to 100C. That's nothing. Iron ore is heated to 1350C, aluminium ore to 1200C.
        And sodium hydroxide turns into salt and water if you add hydrochloric acid. So it is also pretty harmless.
      • Sodium hydroxide and sodium sulfite seem eco-friendly enough: they're easily contained and recycled in practice (and NaOH is easily-neutralized). Even chicken manure is a disaster if washed into streams en masse.

        Trees were the original environmental disaster. Lignin is nigh-impossible to digest; instead, one fungus developed a mechanism to bombard lignin with peroxide, eventually oxidizing a phenyl ring, creating a branched-chain starch. That's digestible via enzymes.

        With a low enough moisture cont

      • by Headw1nd ( 829599 ) on Monday February 12, 2018 @11:40AM (#56108157)
        Since everyone is screaming at each other below this post, I'll leave this here. List of common building materials with their energy embodied in production [lowtechmagazine.com]
    • by ravenshrike ( 808508 ) on Sunday February 11, 2018 @09:16PM (#56105989)

      There's a reason you should have read the fucking article.

      Hu says that his study’s main finding is that removing the right amount of lignin is key to maximizing performance. In his team’s experiments, removing too much of the polymer resulted in less-dense, brittle wood, suggesting that some leftover lignin is helpful in binding the cellulose fibres when they are hot-pressed. The wood was strongest when roughly 45% of the lignin was removed.

    • by Drishmung ( 458368 ) on Sunday February 11, 2018 @09:33PM (#56106027)
      More particularly, what is meant by "strength".
      • Toughness (opposite: brittleness)
      • Stiffness

      How isotropic? (a rope and a bucket of sand are both strong: but the rope is only strong in tension and the sand only in compression). What's the 'strength' to weight ratio?

      For years we've been able to pump wood full of ethylene and then induce it to polymerize, What you end up with is a heavy piece of plastic inferior in almost all respects to the original wood.

      As you point out, cost of working, preservation, reaction with the environment: all of these are hugely important.

      Mild steel is US$500 per ton; Al is US$2000 per ton. It's the cheaper cost of manufacturing that means your beer can isn't steel any more.

      • by Koby77 ( 992785 ) on Monday February 12, 2018 @12:08AM (#56106433)
        I was hoping that the article would contain some actual material properties, such as yield strength, ultimate tensile strength, and possibly elongation. Then we could start making some meaningful comparisons against steel.
      • Mild steel is US$500 per ton; Al is US$2000 per ton. It's the cheaper cost of manufacturing that means your beer can isn't steel any more.

        It's also the lower cost of recycling. It's something like 1/3 the cost to recycle Aluminum, and you wind up with an alloy with identical properties to what you recycled. When you recycle steel, it becomes more brittle, and you have to add things back into it to make it useful again which only costs MORE money. When you combine that with the lower melting point of Aluminum (around a mere 1221 F) — on diesels with Aluminum components, you can literally melt a hole in your engine by cranking up the fuel

    • I wonder if they could vacuum impregnate it with epoxy as an alternative to compressing it.

      • by Leuf ( 918654 )
        That's done all the time to stabilize wood. It makes it more dense and harder, particularly if it was soft from starting to rot (the early stages of rot can be quite beautiful but you have to catch it before it goes too far). It's just not something you can do to anything larger than a turning blank without some serious equipment.
        • Well, yes, I knew that.

          What I meant was, would it make a strong material if they removed the lignin (as described in TFA), but instead of the next step being compression, it was epoxy impregnation?

    • by Cederic ( 9623 )

      Wooden boats are generally good from 15-20 years without major renovations, and are serviceable with major repairs every 10-15 years up to 60-75 years after initial construction.

      I was going to quote a counter-example of a wooden ship under constant military commission for 250 years but.. the facts agree completely with you.
      https://en.wikipedia.org/wiki/... [wikipedia.org]

    • by swb ( 14022 )

      In my experience, both your wooden and steel hulls will need a trip into the yard every couple of years to have bottom paint updated and every so many years they need the whole mess sanded down to the substrate and then a new epoxy barrier coat(s) applied. This amount can vary depending on marine conditions and whether or not the hull is serviced by a diver periodically to clean off marine growth. I know people who get buy 3-4 years on bottom paint with regular dive service.

    • Generally solid wood is a good choice for many projects due to three key reasons:
      1. Cost
      2. Workability; can be worked with hand tools and power tools, glues easily and strong
      3. Water safe for years with no significant prep work

      Whether solid wood is cost effective depends on the application. Sometimes it's a great choice, other times there are better choices. As for workability, again it depends on what you are trying to build. As for water safe, it depends HEAVILY on what you are doing with it. I'm not about to dunk a piece of raw pine in a lake if you get what I'm saying. Most wood of any type requires some sort of coating or treatment to withstand water and remain in good condition for many years.

      Steel is a lot stronger per pound, but to join it you either need to use mechanical fasteners or weld it.

      ??? How many wooden struc

  • Kids (Score:5, Insightful)

    by raymorris ( 2726007 ) on Sunday February 11, 2018 @09:17PM (#56105991) Journal

    TFS says:

    > Attempts to strengthen wood go back decades.

    Decades? Really? People have been firing wood and embedding carbon into its surfaces for at least 400,000 years. This author is off by at least four orders of magnitude.

  • by sit1963nz ( 934837 ) on Sunday February 11, 2018 @09:23PM (#56105999)
    Whats the energy cost vs other materials ?

    Waste treatment ?, what are the by products, how do we dispose of them properly ?

    Recycling of the finished product ?

    Long term stability over time at different temperatures
  • How strong is it versus its weight? I skimmed TFA but didn't find a mention of that. This page [engineeringtoolbox.com] suggests oak, at 3x normal density, would have comparable density to aluminum. If this material is as strong as steel but as light as aluminum, that could have actual applications. I'd wonder about flammability and rotting, though. Skyscrapers or spaceships made out of wood would be pretty funny, though.

    • Dear Click and Clack, My car has termites - please help!

      • Dear Click and Clack, My car has termites - please help!

        Dear reader,
        Pest problems with your Morgan [classicdriver.com] can be addressed by any competent fumigator.

    • Probably lower than regular wood. Dry wood would have pockets of air (oxygen) inside to help spread the fire. Compressed wood, probably not.

  • An interesting point is fire resistance, which can be better for wood than for steel. When heated by a fire, steel bends and structure collapse. That does not happen for wood.
    • Re:Fire resistance (Score:4, Interesting)

      by morethanapapercert ( 749527 ) on Monday February 12, 2018 @12:16AM (#56106445) Homepage
      You're right in that wood does not bend and collapse the way steel does. But what it does do is **feed the fire**. Even wood treated to be less flammable still burns more easily than steel does. (and gives off toxic smoke once the fire overwhelms the chemical resistance. When the wood studs and joists in a home are burned to more than something like 15% of their cross section, they can no longer be expected to carry the load. Wood framed structures collapse more readily than the equivalently steel framed structure. (Note: I am not referring to the thin steel wall studs used to build partition walls, those are never intended to carry any load beyond the weight of the drywall mounted on it. Even a small twist caused by the collapse of an adjoining area totally destroys any load bearing capacity the studs have)
      • Re:Fire resistance (Score:5, Informative)

        by rerogo ( 1839428 ) on Monday February 12, 2018 @01:06AM (#56106537)

        Yes and no. The 2x4s used in standard residential framing burn quite readily. Larger timbers form a protective char [iafss.org], which, as long as it remains on the wood, protects the inner core from fire. If the timber has been specced correctly, the char does not penetrate deeply enough to compromise the structure for some time.

        Steel, meanwhile, is an excellent heat conductor and therefore will start to sag as soon as the outer edge of the steel has reached a temperature that will cause sag.

        • Yes and no. The 2x4s used in standard residential framing burn quite readily. Larger timbers form a protective char, which, as long as it remains on the wood, protects the inner core from fire. If the timber has been specced correctly, the char does not penetrate deeply enough to compromise the structure for some time.

          If the timber has been specced correctly? That's total nonsense. Houses are made almost entirely out of 2x4s and other 2x lumber (but by far, mostly 2x4s) and 2xanythings burn just as readily as 2x4s because of how thin they are.

          Building houses out of flammable materials is insane.

    • Steel melts somewhere around 2,400 degrees, but loses 90% of its strength around the temperature of jet fuel fires.

  • by Anonymous Coward on Sunday February 11, 2018 @09:46PM (#56106069)

    just recycling an infinitely renewable inorganic compound or metal?

    I never followed that "logic".

    Trees grow ridiculously slowly. And no, you can't just plant a few fast-growers (in a mono-culture even) and call it the same as an ancient complex forest eco system that sustained tens of thousands of species in an elegant balance of cycles!

    Meanwhile, metals and generally crystals and materials made from ore are easily recycled in a single day, with some smelting and forging, using only solar energy from places where nothing lives anyway.

    "Stronger than steel" is silly anyway. Steel is not very strong. And what do you mean with that word anyway? There's half dozen things that that can mean, and in none is steel quite the best we have. Steel is only popular, because it is very abundant and very cheap, with acceptable properties.

    Using trees for building things (apart from decorative furniture and the likes) is as stupid as using fields to grow crops to then turn them into gasoline instead of food.

    • Because if your metal goes in the trash, it doesn't come back. The wood doesn't have to be transported or stored in any special way to be renewed.

      • Because if your metal goes in the trash, it doesn't come back.

        Can you explain this? It's not like you click on "empty trashcan" and the metal is deleted. That trash is taken somewhere and emptied into something. It doesn't vanish. It can come back.

        • And assuming that we never manage to make a financially feasible business out of mining in space, I can conceive of old landfills being "mined" for the valuable minerals and stuff that are in there. It doesn't take much gold per ton of raw material to make extraction profitable after all. It's just that current gold extraction techniques would need to change to deal with the fact that the gold is bound up in fiberglass, bakelight and so on, rather than ore.

          In some places landfill mining is already being do

    • by dgatwood ( 11270 )

      Using trees for building things (apart from decorative furniture and the likes) is as stupid as using fields to grow crops to then turn them into gasoline instead of food.

      Even more stupid, at least in the short term, but in the long term, this might actually make sense (whereas ethanol as a fuel will never make sense).

      Imagine this world a few thousand years from now. We've run out of metals suitable for building things, because they're all in use for something. If you want to build a new building, you hav

      • A writer of SF stories who does not know from what our planet is composed ...
        Uh, oh!

    • Poplars grow straight and 50 feet tall in 3 years sometimes.

      We really need to regulate tree farms. There's a lot of cutting of useless forests down in Florida and Virginia--the wood is bent and hollow, no good for anything--and they pretty much use a poorly-written law to get government subsidies for treating the entire natural wetland as "waste product", selling biomass pellets to Europe, and replanting with pine. We should have Federal laws and regulators to ensure logging restores the original habita

    • just recycling an infinitely renewable inorganic compound or metal?

      I never followed that "logic".

      Trees grow ridiculously slowly. And no, you can't just plant a few fast-growers (in a mono-culture even) and call it the same as an ancient complex forest eco system that sustained tens of thousands of species in an elegant balance of cycles!

      Carbon also gets locked up in trees... whilst trees grow, that's carbon out of the atmosphere. Where wood is used to build houses (that's carbon out of the atmosphere)... Yes, obviously it takes burning fuel to build those houses and prep that wood... but it takes even more with steel.

      Trees may grow slowly, but that's all for the best- they provide a habitant for wildlife whilst they grow (regrettably mono-culture isn't the best for wildlife), This also means you need more hectares to get enough for buil

  • lets make sure the QA teams test to see if rodents love the taste of it or not this time around please.

    It was a minor oversight when they switched to Eco-Friendly wire insulation and became an expensive
    problem once the rodents learned how amazing it tasted :|

  • by 140Mandak262Jamuna ( 970587 ) on Sunday February 11, 2018 @10:00PM (#56106123) Journal

    Then the team pressed the block -- like a panini sandwich -- at 100C

    People who read news for nerds might not be able understand what pressing a block means in this context. A highly accurate and technical description, make it so readily comprehensible. Like a panini sandwich! Good, someone might mistake pressed the block something like a burger or a calzone. One might even be thinking of pasta or pilaf or masala dosa. Now it is clear. Press the block like a panini sandwich. Good. Great job.

    • by houghi ( 78078 )

      WTF? Who presses a Calzone? A burger, sure, but only the meat and only if you are a bad cook.

  • by Solandri ( 704621 ) on Sunday February 11, 2018 @10:57PM (#56106269)
    Note that "strength" in this context is per cross sectional area. So taking a block of wood, and compressing it down doesn't change its absolute strength (it can support the same weight as before), but increases its measured strength (load per square mm of cross sectional area before failure). One of the attractions of metals like steel is their isotropic properties - they have the same properties regardless of which direction you load them. Fibrous materials are anisotropic - stronger in certain directions than others.

    Glass fibers are also stronger than steel in tension, but they're weaker in compression and absolutely suck in shear (loading perpendicular to the fibers). The fibers just bend sideways instead of offering any resistance. So we embed them in a matrix of plastic (polyester or epoxy) to create fiberglass. Tensile and compressive strength are reduced, but shear strength improves substantially - enough to where you can walk on a fiberglass board whereas raw glass fibers would simply flop over and let you fall through. Where a fiber used to bend, the plastic matrix absorbs and transmits those forces to other fibers, converting shear forces into tension and compression (the board bows downward in the middle, compressing in the top half, stretching in the bottom half).

    It sounds like what this team has done is taken wood, and cooked it so the cellulose fibers remain but much of the matrix which holds them together has been removed. That has little consequence in tension, but could weaken shear strength to where the material is structurally useless except as rope/cable.
    • Take this "treated, cooked, and compressed" wood, and use it to make plywood.

      • Take this "treated, cooked, and compressed" wood, and use it to make plywood.

        So we're taking wood and treating, cooking, and compressing it, then we're gluing it together. How close have we gotten to the lifetime energy consumption of an Aluminum honeycomb, given that it can be recycled perpetually?

        • Would you like a deck in your backyard made out of a) aluminum honeycomb, or b) 2x4s made by plywood-like construction of this new stuff?
          • Would you like a deck in your backyard made out of a) aluminum honeycomb, or b) 2x4s made by plywood-like construction of this new stuff?

            What? Aluminum, obviously. Why is this even a debate? I'll cover it with all-weather carpet like they use on docks. It'll be lovely and it'll last basically forever.

  • It'd be interesting to see what comes out of this process if they'd used a [real hardwood](http://www.wood-database.com/australian-buloke/)

  • How 'bout a baseball bat made with this process? Could you make a bat that is the same strength or stronger than a regular wooden bat but lighter? Would that be legal for the game?
  • Density or strength (to whatever type of stress) are very relevant features for certain kind of materials, but somehow secondary when thinking about replacing steels or plastics. If you want a strong material regardless of any other thing, you would use something like cement rather than steel. Steels and plastics are strong, but also easily deformable.

    On the other hand, there are some scenarios where flexibility doesn't matter much and steel is used anyway; also "stronger than steel" seems a quite catchy h
  • by cstacy ( 534252 ) on Monday February 12, 2018 @08:03AM (#56107235)

    A Chemical Bath and a Hot-press Can Transform Wood Into a Material That is Stronger Than Steel, Researchers Find

    Why pay $15 a pill when you can just immerse in a bath of our special salts?
    Warning: If you experience "steel" for longer than a few hot presses, contact your chemist immediately.
    Wood will be impregnated, but does not prevent pregnancy.
    May cause blue vision.

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