Wednesday, October 9th, 2013

High-Tech Plastic Fibers Take On Increasingly Tougher Jobs

The Economist magazine’s Technology Quarterly reports on leading-edge tech from every sector, and the latest issue once again has turned to the plastics industry for its newest and coolest. The editors did not, however, focus on obvious targets such as plastics in airplane or car bodies, micro components or another breakthrough medical device.

As the article “Material benefits” states: “…researchers around the world are now cooking up myriad new textiles capable of containing explosions, protecting astronauts, thwarting bacteria and even keeping buildings standing during earthquakes.” Textiles? Really? Yes, new fabrics and threads, small and even delicate as they may seem, are coming out of the labs to solve big — often very big — problems in a variety of sectors.

Air cargo nets of UHMWPE plastic are much stronger to stop loads breaking loose.

Newer air cargo nets of UHMWPE plastic are much stronger to keep loads in place. (Image: AmSafe Bridport)

For example, when a cargo net securing freight in an airplane breaks during takeoff, the load can shift backwards and  raise the plane’s nose enough to cause a stall. All too often the result has been a fatal crash. As a result, several major airlines recently have begun using cargo netting woven from fibers of ultra-high-molecular-weight polyethylene (UHMWPE), a plastic material much stronger than the polyester netting that has been widely used.

The strength-to-weight ratio of UHMWPE fibers is about 15 times that of steel, according to AmSafe Bridport, a British producer of cargo nets made of Dyneema UHMWPE fibers from the Netherlands-based Royal DSM Group. Though the new nets cost about four times more than the traditional nets, the they last longer and weigh about half as much, and that saves fuel, which reduces CO2 emissions. They also are easier to handle.

For this bridge in Houston, TX, Vectran LCP fiber was the lighter and stronger choice over steel cable.

For this bridge in Houston, TX, Vectran LCP fiber was a lighter, stronger choice than steel cable. (Image: Kuraray)

The Economist also describes how the Japanese firm Kuraray Group found a way to pump liquid crystal polymer (LCP) through holes 23 microns (millionths of a meter) in diameter to create fibers that are very thin yet incredibly strong. How strong? You can twist about 100,000 of them together to form a cord a bit thicker than a pencil, with which you can suspend about eight tons. Picture four SUVs hanging by that pencil-thin cord.

Branded Vectran, the material also has excellent resistance to stretching. So along with being excellent for applications such as tape and sails, the material can be used for cabling in robots to help keep their gestures precise. On a larger scale, Vectran cabling was used to retrofita pedestrian bridge over interstate highway 610 in Houston, TX — the lightweight, high-strength alternative to steel. The material also performed well in outer space.

NASA’s Pathfinder, Spirit and Opportunity missions successfully landed their Rover vehicles with the aid of airbags made with Vectran LCP fiber. But the larger size of the Mars Curiosity Rover required a new and much more complex landing system.

The LCP cords in this bridle assembly helped lower the Curiosity  Rover onto the surface of Mars. (Image Courtesy of NASA)

The LCP cords in this bridle assembly helped lower the Curiosity Rover onto the surface of Mars—gently. (Image: NASA)

The Curiosity Rover began its descent from a bit more than a mile above Mars inside an aeroshell traveling about 220 mph. It emerged tethered to a Sky Crane rocket thruster platform that slowed and positioned Curiosity near the surface. Three bridle systems and tethers containing Vectran LCP fiber lowered the Rover 25 feet to a soft landing. (The process is shown in a graphic below.)

The Economist went on to mention several other polymeric textiles used for such non-routine tasks as protecting armored vehicles and keeping buildings from collapsing in earthquakes. However, it did not mention the Dyneema-UHMWPE-fiber cables that held the capsized cruise ship Costa Concordia so it did not slide off its resting place while it was rotated upright last month in a complex 19-hour operation near the Italian island of Giglio. That merits a mention because the ship is more than three football fields long and weighs almost 115,000 tons. Those slender plastic fibers are strong indeed.

 How the One-Ton Curiosity Rover Made a Soft Landing on Planet Mars

Three bridle assemblies used LCP fibers in the last stage of gently lowering the Curiosity Rover onto the surface of Mars.

Three bridle assemblies in the Sky Crane used LCP fibers during the last stage of gently lowering the nearly-one-ton Curiosity Rover onto the surface of Mars. (Image: NASA)


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