Laminating
| The joining of one fabric to another by an adhesive such as natural rubber has long been practiced in rainwear manufacture. Composite materials were later joined by bonding a layer of polyurethane or other foam to a conventional textile fabric. The two components were stuck together by flame bonding or by an adhesive in the form of a continuous coating, in spots, or as a powder. This laminating process has been extended to the joining of two layers of fabric. Each fabric layer can be quite thin, and the amount and type of adhesive are chosen to add only minimum stiffening. Such materials offer a variety of applications. A coating fabric, for example, may be joined to a lining; dimensionally stable composites can be made from cloth layers that are in themselves dimensionally unstable. Acetate knitted fabrics are frequently used as backing material in laminates. Preparatory treatments It is frequently necessary to carry out some preparatory treatment before the application of other finishing processes to the newly constructed fabric. Any remaining impurities must be removed, and finishing processes to the newly constructed fabric. Any remaining impurities must be removed, and to increase whiteness or to prepare for colour application. Some of the most frequently used preparatory processes are discussed below. Burling and mending Newly made goods, which frequently show imperfections, are carefully inspected, and defects are usually repaired by hand operations. The first inspection of woollen and worsted fabrics is called perching. Burling, mainly applied to woollen, worsted, spun rayon, and cotton fabrics, is the process of removing any remaining foreign matter, such as burrs and, also, any loose threads, knots, and undesired slubs. Mending, frequently necessary for woollens and worsteds, eliminates such defects as holes or tears, broken yarns, and missed warp or weft yarns. Scouring When applied to gray goods, scouring removes substances that have adhered to the fibres during production of the yarn or fabric, such as dirt, oils, and any sizing or lint applied to warp yarns to facilitate weaving. Mercerization Mercerization is a process applied to cotton and sometimes to cotton blends to increase lustre (thus also enhancing appearance), to improve strength, and to improve their affinity for dyes. The process, which may be applied at the yarn or fabric stage, involves immersion under tension in a caustic soda (sodium hydroxide) solution, which is later neutralized in acid. The treatment produces permanent swelling of the fibre. Water, used in various phases of textile processing, accumulates in fabrics, and the excess moisture must eventually be removed. Because evaporative heating is costly, the first stage of drying uses mechanical methods to remove as much moisture as possible. Such methods include the use of centrifuges and a continuous method employing vacuum suction rolls. Any remaining moisture is then removed by evaporation in heated dryers. Various types of dryers operate by conveying the relaxed fabric through the chamber while festooned in loops, using a frame to hold the selvages taut while the fabric travels through the chamber, and passing the fabric over a series of hot cylinders. Because overdrying may produce a harsh hand, temperature, humidity, and drying time require careful control. Finishes enhancing appearance Treatments enhancing appearance include such processes as napping and shearing, brushing, singeing, beetling, decating, tentering, calendering or pressing, moiréing, embossing, creping, glazing, polishing, and optical brightening. |