Panels & Furniture Asia Mar/Apr 2018

PANELS & FURNITURE ASIA • Issue 2 • March / April 2018 NEWS 17 WOOD, THE HIGH- PERFORMANCE MATERIAL, JUST LEVELED UP – IT IS NOW BULLET-PROOF THE rise of wood’s renown in bridges and buildings is proof of its strength and durability. Now, a simple, affordable treatment can convert the humble lumber into a material stronger than steel, and even some high- tech titanium alloys, a new research reveals. Besides scoring one for construction, the improved material can also be used in bullet-proof armour. The study, published in the February 7 issue of Nature , reports the simple two-step process: Wood is first boiled in a solution of sodiumhydroxide (NaOH) and sodium sulfite (Na2SO3), a chemical treatment similar to making wood pulp for paper. This partially removes lignin and hemicellulose (natural polymers that stiffen a plant’s cell walls)—but it largely leaves the wood’s cellulose intact. The wood is compressed until its cell walls collapse, then maintaining that compression as it is gently heated. The pressure and heat encourage the formation of chemical bonds between large numbers of hydrogen atoms and neighbouring atoms in adjacent nanofibres of cellulose, greatly strengthening the material. The results show that the wood is three times as dense as the untreated substance, over 10 times more resistant to being ripped apart, 50 times more resistant to compression and almost 20 times as stiff. It is also harder, more scratch-, impact- and moisture- resistant, yet can still be easily moulded into almost any shape. Researchers have long tried to enhance wood’s strength, especially by compressing and “densifying” it but densified wood tends toweaken and spring back toward its original size and shape, especially in humidity, says Liangbing Hu, from the University of Maryland, one of the study’s researchers. In one experiment, five layers of treated wood stopped simulated bullets fired into the material, a result which could lead to low-cost armour. The new material could also open the door to a new class of lightweight materials, with the possibility of applying it in vehicle manufacturing, says Ping Liu, a materials chemist at the University of California, San Diego, unaffiliated with the Nature study. Densified wood also does not require expensive adhesives compared to carbon-fibre composites. It can also be easily recycled. However the research team noted that the widespread use of densified wood will depend on engineers’ ability to scale up and accelerate the process. (Hu and his team spent several hours making each slab of densified wood used for testing.) Still, there is potential for the process to be sped up or used to make larger components, Hu contends. ℗ Source: Scientific American, Nature

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