Science & Technology

This New "Super Wood" Is as Strong as Steel

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Wood is great. It looks nice as a building material. It grows right out of the ground. But compared to things like concrete, marble, and steel, it's not all that strong. Well, it didn't used to be, anyway. Scientists have now created a "super wood" that's strong enough to stop a bullet.

Titanium Strength

This isn't the world's first engineered wood. Chances are, you've got some in your house right now. Plywood, fiberboard, and particleboard are all made by compressing smaller pieces of wood into a single chunk that's stronger than its composite parts. Of those three, plywood is the strongest, since it's made with thin layers whose grain is set at perpendicular angles. You don't have to worry about the wood being weak along the grain because every layer is sandwiched between two others running the opposite direction. But if you want to stop a bullet, we wouldn't recommend jumping behind a plywood barrier. For that, you'll need super wood.

It was surprisingly easy and cheap to create this new kind of wood. Like so many supervillain origin stories, it all starts with a chemical bath. First, you boil the wood in a solution of sodium hydroxide and sodium sulfite. That removes much of the wood's lignin and hemicellulose, two polymers that stiffen the plant's cell walls, but leaves another polymer, cellulose, intact. This part of the process isn't much different than the first step of making paper. It might seem counterintuitive, but removing or weakening these polymers is the key to making ultra-strong wood.

The next step is to start compressing. You subject the wood to enough pressure to collapse the cell walls entirely, then you turn up the heat a bit and keep the pressure going. Unrestricted by the cell walls, the hydrogen atoms of the cellulose begin to form powerful chemical bonds with their neighboring atoms, making the material denser and stronger than ever before. And when we say stronger, we mean it — the wood becomes 20 times stiffer, 10 times harder to break, and 50 times more resistant to compression. It's not just stronger than steel; it's stronger than some cutting-edge titanium alloys. Yeah, we'd say "super wood" is a pretty fair assessment.

The Future Is Clear

There's a lot we could do with a substance that's almost as cheap and easy to produce as paper, stronger than titanium, and lightweight to boot. Here's one idea: body armor. The super wood isn't quite as strong as Kevlar, but it's about 20 times cheaper. It might also become a favorite for building cars and other vehicles because it can grant the fuel-efficient benefits of a lightweight frame without the subsequent rise in price or environmental impact of plastic.

But the way some researchers see it, the incredible strength and stiffness of the wood is only the beginning. Liangbing Hu, the lead researcher behind this super wood, was able to manipulate the material in perhaps an even more striking way in 2016, when he stripped out the lignin (which also lends wood its color) and replaced it with another polymer called methyl methacrylate — also known as Plexiglas. The result? Something straight out of "Star Trek": transparent wood. So your future car might not just be riding on a wooden frame. It could have a wooden windshield as well.

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Written by Reuben Westmaas February 23, 2018

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