Industry folks call it by its correct technical name: silicone-impregnated nylon. Marketers and consumers, on the other hand, have an aversion to “impregnated” gear; they use more benign names like siliconized nylon, or silnylon for short. Whatever you call it, this slick fabric is arguably the biggest new material to hit the outdoor market in the past decade.
In silnylon, each individual nylon fiber is surrounded by silicone, giving the fabric a slippery, almost greasy feel. The silicone significantly improves tear strength, allowing manufacturers to use lightweight threads and still achieve the same level of performance as heavier, polyurethane-coated alternatives. “If you take a regular nylon, one treated with a polyurethane coating, and one with silicone, the silicone version will have twice the tear strength,” explains Kevin Joyce, director of products for GoLite, an industry leader in ultralight gear. “At the same tear strength, a silicon-impregnated nylon will be 30-35 percent lighter than the polyurethane equivalent.”
Roger Caffin, senior editor of technology for Backpackinglight.com, elaborates. “Normal polyurethane-coated fabrics have a layer on only one side, which sits on the surface and can be peeled off,” he explains. “Silnylon is coated on both sides with a thin film of silicone polymers. The silicone is much more water-like than polyurethane when it is first applied, allowing it to wick along the fibers and bond throughout the material. This is an important point—think of silnylon as a thin sheet of silicone polymer reinforced with fabric. Tear strength is higher because the silicone is also somewhat elastic, which spreads tension over more threads. It absorbs energy, stretches a bit, and then pops back.”
These properties have allowed gear manufacturers to radically decrease weight, especially in tent design. As recently as five years ago, any standard, double-walled two-person tent that weighed less than 6 pounds was on the lightweight side of the spectrum. Five pounds has now become the benchmark—and several of today’s lightest versions are less than 4. GoLite began using silnylon in its tent line in 1999, but it has hit the mainstream only recently. These days just about every gear manufacturer incorporates it in their ultralight lines.
Silnylon is also appearing in an increasing variety of stuff sacks, but only to a limited extent in other gear. Why? Silnylon is extremely thin stuff, making it less resistant to puncture and abrasion. This isn’t an issue for tents, where tear resistance—especially the ability to withstand strong winds without shredding—is the essential property. It’s a significant problem, however, for equipment like packs or clothing, where a single bushwhack could wreak havoc on the material. Silicone also bonds poorly with other materials—such as nylon repair tape and seam sealer—making it difficult to repair damage. Plus it’s pricey; expect to pay about 50 percent more for anything made with silnylon.
But if you’re after weight savings, you can’t beat this slippery stuff. And it’s only going to get lighter. In 2010, GoLite will introduce a new ultralight silnylon that weighs 20 percent less than what’s currently available and still retains 98 percent of its tear strength. Caffin expects to see even greater improvements in the years ahead: “We haven’t reached the end of the road in fabric-coating technology by any means.”