Armor Holdings' product is different from all of the above. Developed by Norman Wagner, a professor of chemical engineering at the University of Dela-ware's Center for Composite Materials, it's a mix of polyethylene glycol, a polymer found in laxatives and other consumer products, and nanobits of silica, or purified sand. Together they produce a "sheer-thickening liquid" that stiffens instantly into a shield when hit hard by an object. It reverts to its liquid state just as fast when the energy from the projectile dissipates.
LIKE PEANUT BUTTER
Initially, Wagner and his collaborators envisioned armor that could be spread on a person, almost like peanut butter on bread, says Eric Wetzel, a researcher at the Army Research Laboratory in Aberdeen, Md. But in tests co-sponsored by the Army Lab, they found that the materials worked best when painted on Kevlar in ultrathin coats. By holding the fibers tight like a flexible glue, the compound spreads out the impact of a blow better than fibers alone. "The search in the past has been for stronger and stronger filaments," says Wetzel. "We've tried to change how the fabric interacts with the projectile."
The liquid has other pluses. It's lighter than Kevlar and other widely used fabrics. That means Armor Holdings' new vests, in which the substance would be sandwiched between layers of ballistic fibers, might be lighter than current versions, which weigh four pounds or more. It also should be cheaper to manufacture, says Schiller. The Jacksonville (Fla.) company wants to continue to sell entry-level garments for $500 to $600.
Sweet. Sent by Skinny Bean of Denver, CO.