Fabrics, coatings and finishes
Coatings customize fabrics for the perfect match with customers’ applications.
Specialty Fabrics Review | December 2009
By Barb Ernster
There are countless combinations of fabrics, coatings, finishes and coating methods to achieve different specifications for a wide spectrum of applications. From simple vinyl tarps to highly engineered ballistic liners, the coated fabrics industry is more diversified than ever and encompassing more markets as new—and old—coatings and techniques prove successful in their applications.
Whether you need a product that can withstand chemicals, extreme cold or hot temperatures, or that can be heat-sealed or welded, the question becomes not only which coating, but how many of the desired properties should come from the base fabric itself. It all depends on the application, say industry sources.
Start at the ending
“Start with the end result you’re looking for, then build a fabric to meet those requirements,” suggests David Manning, president of Sattler North America in Melville, N.Y., which creates special use fabrics and membrane solutions for the outdoor fabrics industry. The fabric substrate—whether cotton, polyester, nylon, Kevlar®, Fiberglas®, knit or woven—will determine the base properties, tensile strength, stretch, durability, diagonal control, flammability, moisture resistance and breathability.
The coating, which might be from wax, PVC, plastisol, urethane, neoprene, acrylic, rubber or blended polymer, enhances the fabric’s performance and achieves the different effects that the fiber cannot, such as resistance to water, mildew, UV and chemicals, fire retardancy, and cut and puncture resistance.
To get the right performance between fabric and coating, it falls on customers to educate themselves on their application and the specifications required to meet that application, notes Edward Silva, vice president of sales and marketing at Cooley Group in Pawtucket, R.I., a chemical and engineering company that creates its own polymer blended coatings on flexible membrane substrates.
“All industrial fabrics are not created equal,” says Silva. “I can have the greatest product in the world at the most competitive price, but if it’s used for the wrong application, it won’t work.”
Methods and markets
Many of the newest polymer technologies are more advantageous when melted and applied through an extrusion process, says Silva. The biggest benefit of extrusion is that the polymer is kept in its purest state without adding more chemicals or solvents to effectively process the polymers while still meeting the performance requirements.
Cooley Group also produces its own woven and knit fabrics, which helps them test new products and accommodate custom requests, particularly for some of the newer demands in military applications, water conservation and chemical storage applications. Forty percent of its business is in new solutions that are developing new markets.
Buckeye Fabric Finishing Co. in Coshocton, Ohio, uses the classic floating knife method coating to produce wax coatings for cotton, cotton flannel, cotton/polyester and cotton/nylon fabrics. Wax-coated cotton can provide a less expensive, environmentally friendly, breathable, flame-resistant, water-resistant and mildew-resistant product for outdoor covers and many other military and commercial uses.
“It’s still very relevant today, sort of like blue denim jeans. It’s been around for a long time, but is still very popular,” says Kevin Lee, president of Buckeye Fabric Finishing and its sister company, Excello Fabric Finishers Inc.
Excello uses vinyl and acrylic coatings that are heat fused onto cotton, cotton blends, polyesters and some nylons to achieve different performance results for higher end uses, such as marine covers, awnings and tents. Vinyl coatings are flexible at low and high temperatures and perform well in various environments, but may not be as water resistant as wax-coated cotton unless top coated, says Lee. Acrylic, water-based coatings also exhibit good performance in extreme temperatures, are environmentally friendly and are compatible with polyester fabrics.
Buckeye and Excello offer their customers a variety of standard industrial coatings from which to choose and frequently act as custom coaters as well. The companies have assisted clients with the development and application of a variety of wax and nonwax coated apparel coatings, adhesives, rubber backing and insulation products, all with smaller minimum order quantities than many larger manufacturers.
BondCote Corp. in Pulaski, Va., sources its own fabric substrates and matches them with customized PVC coatings to achieve exact specifications for the customer’s needs. It produces a wide variety of coated and laminated fabrics for military, agricultural, athletic, inflatable, marine, roofing and other commercial markets. The company mainly works with polyester, which provides good dimensional stability, tensile and tear strength, while the polymer coating adds flexibility, as well as UV-, abrasion-, flame-, water- and mildew-resistance. Acrylic or polyurethane topcoats may be applied to add cleanability, slip, oil resistance, waterproofing or aesthetic properties. BondCote also coats nylon, glass and blended fabrics.
“Price point is always a topic of discussion. It relates back to the application, the specification and the total requirements that the customer is looking for,” says Wayne Holden, commercial technical manager at BondCote. “Many of our coated and laminated fabrics are developed to support specific technical needs of our customers.”
Higher performance means higher costs. While PVC is considered the most economical coating, there are only so many uses you can get out of it, and you have to look to polyurethanes and other chemical additives to get higher performance, notes Chris Semonelli, vice president of sales and marketing at Erez USA in Newport, R.I. Producing coated fabrics for marine and safety products, athletic and medical, roofing, architectural and tension structures and flexitanks, Erez tries to match the point in its PVC/urethane blends that gets the best performance at the right price for the market.
Different grades of urethane will meet particular specifications. Ester grade urethanes are more fuel resistant, but need additives when exposed to moisture. Ether grades are more stable in a water environment and better for such uses as potable water containers. Aliphatic grades work in both water and fuel environments, and provide better ultraviolet and abrasion resistance when applied as a topcoat.
“We’re definitely playing with new coatings and new blends and introducing them in new products,” Semonelli says. With the evolution of thermal plastics, the polyurethane family has started to displace the rubber products. In fact, DuPont™ announced in May that it will cease production of Hypalon®, a chlorosulfonated polyethylene rubber, due to decreasing sales volume in all end-use market segments. Semonelli says the benefits of polyurethane over rubber is that you can heat weld rather than glue it, which saves time and money. He predicts that thermoplastics will continue to evolve and replace some coating products, while new polymer blends will expand markets and open new ones.
Many companies are seeing greater demand for lightweight textiles with waterproof, breathable properties for military, outdoor recreation and other applications. Sattler North America makes a breathable, waterproof woven acrylic for boat covers called Nautex Premium that is three times more waterproof (900mm in water column tests) than standard marine fabric. The solution-dyed fiber is first put through a finishing bath to make it water resistant, cleanable and mold and mildew resistant, then a thin coating is applied to make it more water resistant and breathable.
“With this fabric, when the sun is shining, it allows the humidity inside the cabin to evaporate, but maintains a high degree of waterproofness on the outside. I believe we’re the only ones in the world doing it,” says Manning.
With increasing demand for high performance, lightweight products, HDM Inc., in Oakdale, Minn., offers a product called SuperFabric®, made by screen printing an engineered polymer in geometric patterns onto multiple substrates, offering extreme cut, puncture and abrasion resistance, among other properties. The product, developed by HDM CEO and physicist Young Hwa Kim 12 years ago, is used in military and law enforcement gear, outdoor apparel and footwear, luggage, safety gloves, backpacks and other high-performance applications. HDM’s new roll production capabilities are opening up even more applications.
“You can take an ordinary 500 denier nylon or 600 denier polyester and after we’re done printing, it increases abrasion and cut resistance exponentially. The screen printing allows it to maintain flexibility,” says sales manager Chris Kohn.
Swiss-based Schoeller Textiles in Seattle, Wash., has developed an extremely water-, dirt- and stain-repellent finish based on nanotechnology. NanoSphere® combines nano particles with a nano gel and forms a nano-structured surface that causes water, oils and dirt particles to run off. It was developed and is applied in accordance with the bluesign® standard, assuring ecological safety.
“With coatings, there’s always the issue of compromising the breathability of the fabric,” says Tom Weinbender, president of Schoeller U.S.A. “[NanoSphere] doesn’t plug the holes, it only covers the fiber surface, and has no effect on the hand or the breathability of the fabric.”
There are many different qualities that can be achieved with coatings that cannot be obtained through other means. With new coatings and technologies entering the market, and continued demand for older methods and compounds, fabric coatings are likely to play an ever-increasing role for customers when making fabric choices.