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An Overview of Geosynthetics Chap. 1 others by manufacturers such as Chemie Linz in Austria and Du Pont and Miraii in the United States has continued, thereby introducing geote.'itiies on a woridwide basis. To day. many manufacturers are involved in the production, sales, and distribution oi geo- • » textiles. See section 6.4. A number of conferences have been held on the subject ot geotextile.s. the major ones being those held in Paris [6] in 1977. in Las Vegas in 1982 (7], and in Vienna in 1986. Furthermore, the original two books on the subject have appeared almost simulta neously. thL se of Koemer and Welsh [8] in 1980 and Rankilor (9) in 1981. Today, addi tional books along with many hundreds, perhaps thousands, of separate papers and reports are available dealing with geotextiles, and two journals have recently been launched dealing exclusively with geosynthetics [10. 11]. This massive generation and dissemination of information was led initially by fabric manufa'^turers. Their influence in this market continues to be active and indeed is very positive and welcome. It has been followed by the entire community of manufacturers, govemm.enial. industrial, con sulting. research, and academic institutions 1.2.2 Manufacture As noted, the role of the fabric manufacturer in the stimulation and growth of the geo textile market has been both large and positive. Many fiber types and fabric styles have been developed both for general use and for specific applications. In fact, it seems that these two approaches toward the marketing of geotexiiles represent the current situation: manufacturers w'ith one basic fabric style (usually available in different weights) and manufacturers having a variety of fabric tv'pes. targeting each to a specific application. Three points are imponant insofar as manufacturing is concerned: type of polymer, type of fiber, and fabric style. Each will be discussed separately. The fibers used in geotexiiles are made from the following materials, listed in order of decreasing use: Polypropylene Polyester Polvamide (nvlon) Polyethylene Other polymers and glass The vast majority are hydrocarbon derived (i.e., from oil); hence it should come as no surprise that the petrochemical industries of the world are heavily involved in the geo textile market. See Appendix 6.3.1 for the chemical structure of the various materials. The chemical and environmental endurance properties discussed later in the book are very dep>endeni on the ty'pe of polymer used in a geotextile’s consruction. Some typical properties of polymeric materials used in the construction of geotextiles are given in Table 1.1. The basic polymers are made into fibers by melting them and forcing them through a spinneret, similar in principle to a bathroom showerhead. The resulting fiber filaments are then hardened or solidified by one of thi.,!. methods: wet. dry. or melt. Most geoiextile producing fibers are made by the melt process: these include polyolefins kiA