There are no easy answers or “magic” fibers, yarns, finishes, and coatings to meet every application.
Fabric Graphics | March 2007
By Phil Age and Jean K. Dilworth
Selecting the best fabric for your final application or product depends on the manufacturer’s method of creating fabric from fibers and yarns. The fabrication contributes to the appearance, product end use, cost, and durability. The four fabric variables: fiber + yarn + structure + finish = specialty fabric, may be changed to provide the best specialty fabric for the product. Ongoing research and innovation in specialty fabric production provide improvements in existing products and the development of exciting new ones. Today more than ever, specialty fabric propels projects into a new world of design and functionality.
Fabric manufacturers and suppliers are asked daily about new develop-ments and applications. Proper terminology will help you ask better questions about inkjet printing directly to fabric. Here are common terms to assist you for fabric purchases and product considerations.
There are three primary methods of fabric structure used for inkjet printing. They are wovens, knits, and vinyl substrates.
Wovens. All woven fabrics are made with two or more sets of yarns inter-laced at right angles. The fabric is woven on a mechanism called a loom. Warp yarns are stretched lengthwise on the loom; fill yarns are interlaced with the warp yarns in a variety of patterns from simple plain weaves to intricate jacquard weaves. Woven specialty fabrics are found in applications that require the stability provided in the perpendicular directions of the warp and fill yarns.
Knits. Knit fabrics are made by needles forming a series of interlocking loops from one or more yarns or from a set of yarns that create their structures. Filling knits are structured with rows of yarn loops layered horizontally; one row interloops with the other. Filling knits provide the crosswise stretch in the fabric. Warp knits are structured with rows of yarn that are laid in the vertical direction of the fabric and provide little stretch.
Vinyls. Vinyls (flexible PVC) consist of two PVC layers with a polyester support fabric (scrim) base that provides some opacity. These vinyls often are used for banners and signage.
Fabric structure types vary as indicated above. However, all fabrics are composed of yarns made from individual fibers, which have generic names, brand names, and specific chemical and physical properties. The primary fibers used for direct to inkjet printing can be divided into two categories: synthetic or natural. Synthetic fibers are petroleum-based products and are made by an extrusion process. The most popular synthetic fibers are polyester (terephthalate polymers-PET), nylon (polyamide), and olefin (polyethylene) and can be engineered for specific purposes. Natural fibers are produced from plant (cotton and flax) or animal (silk and wool).
Manufactured fibers present new opportunities to engineer unique attributes into a specialty fabric. Different chemical formulations then make various fibers. Each fabric only can have the chemical and physical properties of its fibers unless further treated. For example, nylon (filament 4.0-7.2 dry g/d) and polyester (filament 2.8-5.6 dry g/d) have excellent tensile strength. Tensile strength is measured in grams per denier, which refers to weight per diameter of fibers, yarns, and sets of yarns (bundles). But nylon is weakened by sunlight (UV rays) where polyester is not weakened to the same extent. Synthetics are sensitive to heat and will shrink or melt if not stabilized by heat setting. Nylon can be modified to improve its resistance to sunlight. Each fiber requires a specific dye or pigment ink. For example, polyester requires disperse dyes, and nylon and silk require acid dyes for the best results. If you choose cotton, reactive dyes are required for the product to be washable.
Fibers are further divided depending on their length. Short fibers are referred to as staple fibers that result in spun yarns and create a softer texture and a matte surface of the fabric. The long fibers that are found in silk and all synthetics are filaments that result in a smoother and a greater gloss to the surface. Filament fibers are sometimes cut into staple fibers (shorter lengths) to create spun yarns for fabric specifications.
A quick resource to check is the Web site www.fibersource.com. This site has terminology, properties, and history of major synthetic fibers including the Federal Trade Commission definitions for each.
Finishes and coatings are applied to fabrics to improve their performance for specific purposes. Heat settings, UV inhibitors, flame resistance, waterproof, stain resistance, and inkjet printing are all considered as finishes in this context. Inkjet printed colorants are considered finishes. All finishes and printing processes have unique specifications that you must verify with your supplier.
Inkjet printed colorants either bond chemically with the fiber molecules (dyes) or are held on the surface of the fabric by a binding agent (pigments). More than 80 percent of the printed fabrics in the U.S. market are printed with color pigments. Fabrics printed with pigments do not require most of the postprocessing steps required of inkjet water based dyes. Water based dyes are either acid, reactive, or disperse dyes and are specially used on protein (silk, nylon), cellulose (cotton, flax), polyester (PET), and polyurethane.
Selecting the best fabric
Each variable in the formula of fiber + yarn + structure + finish = specialty fabric is carefully selected to perform in a specific way. The end result is a specialty fabric engineered for its intended end use. A change in just one of the variables can produce a unique specialty fabric with its own specific attributes. It is clear that innovative thinking combined with the technical properties of specialty fabric have made it one of the most versatile materials in the world.
You, as a printer or purchaser of digital printing, need to ask questions about the fabirc. There are no easy answers or “magic” fibers, yarns, finishes, and coatings that meet every application.
Fabric choice will depend on the inkjet printer and ink combination, fiber properties, fabric structures, and finishes needed to meet your requirements.