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Liangbing Hu at UMD, checks out. Fantastic find! This should at least be the top comment on this thread to offset the content-free journalist pablum that's linked. The strength is 483–587 MPa, I seem to see when skimming, which is indeed superior to ASTM A36 structural steel (250MPa yield strength). In Extended Data Figure 1c, they reported the density as 1.3g/cc, a sixth of the density of steel. (Extended data figure 2f plots density against lignin removal percentage.) Of course high-strength steels are stronger, but not six times stronger. As for the process, they didn't just boil the wood; they boiled it with lye (2.5M, the "food industry chemical") and sodium sulfite (0.4M, technically also a food industry chemical, used for example as an antioxidant in wine) for 7 hours before densifying it with 5MPa for "about a day", removing optimally 45% of the lignin. This is similar to the sulfite chemical wood pulping process that preceded the Kraft paper process, just carried out at high pH and not taken to completion, so in a sense I guess the result is sort of like Masonite, which is also made from cellulose fibers from wood bonded with the wood's natural lignin. Environmental concerns may be an obstacle; sulfite pulping is nasty. Also presumably to mass-produce the stuff they'll want to find ways to shorten the cycle time, and maybe already have. The burning question that arises in my mind is why nobody was doing this in 01890, 135 years ago. Sulfite pulping was going gangbusters, building materials were booming, environmental concerns were largely unknown, and there was a rage for everything newfangled, modern, and "scientific". The scientific discipline of strength of materials, needed to calculate the benefits, was already well developed. Mason put Masonite into mass production in 01929, with a process involving autoclaving wood chips at 2800kPa. So what prevented someone from selling Superwood back then? Did nobody try partial alkaline sulfite pulping and pressing the result? |