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Flexible fabric composites

September 1st, 2011 / By: / Advanced Textiles, Feature, Markets

The versatility of flexible fabric composites opens doors to new products and markets.

Fabric composites have been around for decades, and thanks to ongoing technological improvements in these materials, applications and markets continue to expand. As a result, fabricators have more opportunities for creating a flexible end product that ranges anywhere from a sail on a yacht to a hazmat suit. What’s more, for many of these applications, end product manufacturers can use the equipment that’s already in their shops.

Flexible composites, versatile applications

A fabric composite—sometimes called a textile composite or flexible composite—is a material comprising disparate components combined to form a finished product that has different properties than each component could achieve alone. Vinyl-laminated fabrics and some coated fabrics fall into this category. Depending on the application, flexible composites use textiles such as cotton, polyester, nylon and silk, as well as high-performance fibers including Kevlar®, Nomex®, Technora® and Vectran®. Nonfabric materials could include natural or synthetic rubber, silicon and polyurethane or polyolefin coatings. Fabric composites are used in countless markets, including military, aerospace, industrial, medical, and sports and recreation.

“One of the main advantages of flexible membranes and composites is that they are lighter weight,” says Darius Shirzadi, product and business manager of the Engineered Membrane Division at Cooley Group, Pawtucket, R.I. “Depending on the polymer, they can have very high chemical and temperature resistance and can go into a variety of different environments.”

Cooley Group’s membranes have been used in a variety of projects. For oil spill containment booms, as an example, fabric composites are often recommended because they can resist extreme cold or heat, are UV stable and require little maintenance other than the occasional cleaning. Plus, end users don’t have to worry about metal corroding or wood rotting.

Fabricators have also made flexible bladders to hold fuel and clean drinking water for U.S. troops in Iraq and Afghanistan. “The fabrics are getting more complex and their designs are improving every day,” Shirzadi says. “Membranes are easier to transport as well.”

Trelleborg Engineered Systems in Taylors, S.C., also targets the military with many of its flexible composites. A soft armor system applied to the exterior of a Jeep or Humvee can keep explosions (such as those caused by driving over a mine) outside the vehicle, protecting the soldiers inside. Fabric composites are also used to make bags that hold metal boxes with ammunition. In the event of an explosion, the bags prevent bullets and shrapnel from flying everywhere.

Trelleborg’s materials have appeared in everything from fluid-handling materials to shoe covers worn in operating rooms and electronics clean rooms. With fabric composites, “you’ve got something pliable that can be formed and cut easily,” says Ben Cox, vice president of sales and marketing. “They have a mix of strength and flexibility.”

Light, but tough

In many instances, a project that successfully uses a flexible composite can lead to additional applications. For example, Warwick Mills in New Ipswich, N.H., developed specialized weaving technology for the crash attenuation bags made of flexible composites for NASA’s Mars Pathfinder mission in the mid-1990s, then adapted the technology into a product line called TurtleSkin®.

“We took what we learned from the Pathfinder project about how to weave fibers tighter than ever achieved before and developed a family of products that offers high puncture resistance, along with specialized coatings and laminations,” explains Leslie Richardson, Warwick Mills technical sales. The manufacturer was able to create puncture-resistant safety gloves and law enforcement gloves, as well as snakeproof garments, using TurtleSkin, which is made with high-performance synthetic fibers such as aramids and Vectran®.

In addition to puncture resistance, the material offers characteristics such as a high tensile strength-to-weight ratio and durability for applications including inflatable tents and chemical/biological-protected shelters, flexible antennas, seals for nuclear plants, special filters for the automotive industry, breakwaters for flooded areas and aerospace inflatables like airships.

Fabric composites are often used for heat-resistant applications, which have become a specialty of Thermal Control Products Inc. in Concord, N.C. The fabricator manufactures multilayered soft and flexible heat shields, which perform like an “oven mitt” for the exhaust system of a race car. The company manufactures a variety of shields that are capable of handling continuous-usage temperature ranges from a few hundred degrees Fahrenheit up to and more than 2,000 degrees.

“[The shields] encapsulate the heat that is being emitted from the exhaust system from penetrating the driving compartment,” explains Thermal Control Products vice president Paul Matte. “The heat shields have longevity and durability and offer ease of assembly. They have to be easy [for the racing crew] to install, and easily removed.” Other uses for the heat shields include commercial transportation and industrial applications. In some cases, customers have them designed for their noise-abatement properties, serving a dual purpose.

Sustainability matters

Sustainability has been and is a hot topic for both fabric suppliers and end product manufacturers in most segments of the specialty fabrics industry, and it’s a growing part of the conversation about flexible composites as well.

“Sustainability is going to be vital for our industry, but the materials are not what you’d typically consider environmentally friendly,” Cox says. “Just like tires, they are difficult to recycle and reuse directly.” To that end, Trelleborg is working with polymer suppliers to help develop new technologies that enable direct recycling. “We have also converted a variety of our materials from traditional rubbers to thermoplastics like urethane to give us that ability to reuse and recycle,” Cox adds.

Barriers to sustainability exist on the manufacturing side, too. “You have inherent waste in creating a composite fabric, and there are a lot of environmentally unfriendly solvents involved,” Cox adds. Still, it’s not impossible to go green, as Trelleborg has demonstrated. “We recover over 99 percent of the solvents and reuse those chemicals continuously to avoid putting them out in the environment or creating handling streams to deal with that by-product.”

Customer demand is a driving force as fabric composite manufacturers and fabricators introduce more eco-conscious practices. According to Shirzadi, increasing numbers of people in the industry are moving away from heavily plasticized products because the binders used in them aren’t good for the environment. “Environmental and medical industries are especially moving toward a technology that does not have those types of chemicals involved,” Shirzadi says. In addition, Cooley Group recycles some of its materials by separating plastic polymers from the fibers of used flexible composites and reuses the reclaimed material in the manufacture of a new membrane, in lieu of using 100 percent virgin material.

In some applications, fabric composites can be green while helping end users save green. Auburn Manufacturing Inc. in Mechanic Falls, Maine, recently introduced Ever Green® Cut ’n Wrap™, a modular insulation kit designed to cover bare piping components in both steam/hot water and chilled water heating and cooling systems. The composite, made of various high temperature-resistant fabrics such as fiberglass, as well as various needled fibrous insulating materials, can reduce heat loss by at least 85 percent.

“The inside insulation is eco-friendly, with no environmentally damaging finishes, and the coating is 100 percent solids based, so there is no waste in the coating process,” explains Kathie Leonard, CEO of Auburn Manufacturing. Easy assembly is another hallmark of the product. “Insulating covers that were once handmade are now quickly made on-site from a kit,” Leonard says.

Looking forward

The evolution of flexible fabric composites will likely include enhancements in technologies that will lead to new and better applications. “We’ve created materials that let somebody move comfortably into a biohazard area,” says Cox, nothing that Trelleborg’s fabric composites appear in the protective suits of people working with the damaged nuclear plant in Japan. “Before this, you either sacrificed people’s lives or waited around until it was safer to go in.”

Over the last five to 10 years, new needle-stick protections have hit the market, as have improvements in flexible body armor for the military, police and corrections officers, says Richardson. Similar composites can be used for lightweight protection for ultra-high-pressure water jet operators.

QinetiQ North America Inc. in Waltham, Mass., is delving into electric fabrics for the military. In such an application, wires would be woven into a narrow fabric attached to a soldier’s uniform. The result: wearable sensors that can detect where a gunshot is coming from.

Cooley Group is exploring the role of solar power in composite fabrics. In June 2010, the company launched its first lightweight solar-powered billboard system constructed from its Enviroflex® substrate, which was integrated with a thin-film photovoltaic (PV) system. “It’s possible for the integrated system to generate electricity and potentially project images down the line,” Shirzadi says.

As an end product manufacturer, what Thermal Control Products could really use is “a really good aluminized composite made up of a sandwich of aluminized fiberglass or silica cloth with an isolative nonwoven, rather than me putting something together and layering it,” says Matte. “All I’d have to do is cut and finish it. That would cut out a step or two in the manufacturing process.”

Holly O’Dell is a freelance writer based in Pine City, Minn.

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