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I- <br />An Overview of Geosynthetics Chap. 1 <br />tinuous filaments are then laid on a moving conveyor belt to form a continuous web. In <br />the lay-down process, the desired orientation of the fibers is achieved by various means, <br />such as rotation of the spinneret, electrical charges, introduction of controlled air- <br />streams, or by varying the speed of the conveyor belt. The fabnc is then bonded by ther­ <br />mal, mechanical, or chemical treatment before being wound up into finished roll form <br />(see Figure 1.4). <br />A wide range of fabric characteristics can be achieved by controlling the various <br />elements in this process. High-performance low-weight fabrics are characteristic of this <br />process because of the continuous nature of the fibers. Fabric weights usually range <br />from 0.3 to 6 ounces per square yard. Thickness generally ranges from 3 to 25 mils. <br />Typical end uses are as coated and laminated fabrics, carpet underlay, packaging mate­ <br />rials, durable papers, sanitary napkins and diaper covers, filtration, interlinings, dispos­ <br />able apparel, wall coverings, battery' separators, and building materials, and, of course, <br />as geotextiles. <br />1.2.2.2 Melt-Bonded Process <br />These fabrics consist of continuous filaments or long stable fibers that are melt <br />bonded together at filament or fiber crossover points. The resultant fabrics are rather <br />tough and compact in appearance. Higher product strength can be achieved with this <br />{13}.) <br />i. ri: