Sign & Digital Graphics

October '19

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What has contributed to that growth? My opinion is many things have con- tributed to it in the last five years or so. You really need to start with the print- heads themselves. They have become much more reliable, and the speed has increased rapidly. The firing frequency of the printhead and the print quality has drastically improved. In fabric printing, it is important to understand the chemistry in the process. There is no single ink type that will ade- quately print to all fiber types in a simple, one-step process. That is the reality, and it means we must understand how dif- ferent types of fibers interact with the available ink choices. The main ink types used in digital textile printing can be viewed in several different ways, but we tend to classify them by the colorant used, such as dye- based inks and pigmented inks. Ink types include: • Dye • Reactive • Acid • Disperse/Sublimation dyes are vari- ants of the same chemistry with differing physical properties in printing processes but printing on the same class of materi- als (mainly polyester). • Pigment Reactive dye inks react chemically to bond with the fiber substrate. It is typi- cally used on natural cellulosic (plant) fibers such as cotton and linen. Rayon is S I G N & D I G I T A L G R A P H I C S • October 2019 • 57 also a cellulosic fiber, but it goes through more extensive processing than some other fibers. Silk, although a protein fiber, can also be successfully printed with reactive dyes. This ink chemistry provides vibrant colors, excellent wash- fastness and may be dry-cleaned. In reactive printing, the fabrics are pre-coated before printing. After print- ing, the fabric is steamed, creating a chemical bond with the cellulose in that fabric. The fabric is then laundered and ironed and mainly used for garments. Many companies are considering switch- ing to pigment inks to avoid pre- and post-processes. Acid dyes are primarily used on pro- tein (animal) fibers like wool and silk but are also used on nylon acrylic, polypro- pylene and blends of these fibers. Acid dyes are so-called because they utilize an organic or inorganic acid compo- nent in the chemistry rather than the alkaline component for reactives. They also provide vibrant colors and excellent wash-fastness and may be dry-cleaned. When we discuss digital-printed textiles, we group the finished printed product into four major categories: CLOTHING, which includes things like dresses, fashionwear, jackets, underwear, T-shirts and sportswear. HOUSEHOLD ITEMS like carpet, drapes, pillows, upholstery, tablecloths, towels and wall coverings. DISPLAYS/SIGNAGE used for banners, soft signage, flags, trade show banners and graphics and entertainment. INDUSTRIAL textile printing is usually items you would see inside of automobiles, such as printed seats, seat belts, panels or items like tents, medical items, bags or covers.

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