Geotextile materials nonwoven geotextiles

Composite geotextiles are formed by the integral combination of two geotextile types into a single (composite) geotextile material nonwoven plus nonwoven or woven plus nonwoven. The resulting composite stmcture exhibits the positive attributes of both component parts. Fig. 20.1(c) shows the stmcture of a woven—nonwoven composite geotextile. 

Olefin fiber is an important material for nonwovens (77). The geotextile market is stiU small, despite expectations that polypropylene is to be the principal fiber in such appHcations. Disposable nonwoven appHcations include hygienic coverstock, sanitary wipes, and medical roU goods. The two competing processes for the coverstock market are thermal-bonded carded staple and spunbond, both of which have displaced latex-bonded polyester because of improved strength, softness, and inertness. 

Geotextiles may be woven, nonwoven, or knitted. AH types, woven, nonwoven, or knitted, are susceptible to degradation owing to the effects of ultraviolet light and water. Thus stabilizing agents are added to the base polymeric material to lessen the effects of exposure to ultraviolet light and water. 

In nonwoven geotextiles, the fibers are much thinner but far more numerous. The various types are needle-punched, resin-bond, and melt-bond. All contain a labyrinth of randomly oriented fibers that cross one another so that there is no direct line of flow. The fabric must have enough open space to allow liquid to pass through, while simultaneously retaining any upstream movement of particles. The needle-punched nonwoven type is very commonly used as a filter material. 

Geotextiles are the polymeric textile materials that are widely used in civil engineering to provide reinforcement, filtration, separation, drainage, erosion resistance and asphalt reinforcement. They take many forms nonwoven and woven textiles, grids, and openwork structures sandwiched between layers of nonwoven for lateral drainage. The principal... 

Chemical bonding. A binder such as glue, rubber, casein, latex, cellulose derivative, or a synthetic resin is used for bonding the filaments or short fibres together and these materials are known as chemically or adhesive bonded nonwoven geotextiles. 

Depending on product functions, reclaimed fibres can be looked upon as conventional in technical textiles, particularly in nonwovens (mobility textiles which mainly serve to cover up surfaces or to insulate materials, agrotextiles, and geotextiles which are used to protect soil against erosion). In all these cases, reclaimed fibres are used because of low prices, or because they merely cover something up. However, reclaimed fibres are also applied in nonwovens to utihze highly valuable functional components. This concerns fibres which would not be available at a competitive price if made from primary materials, such as... 

Table 3.5. Transition temperatures (in °C) of thermoplastic materials used for geosynthetics (geomembranes, nonwoven geotextiles, geocomposite drains, geogrids etc.). In addition to polyolefins PE and PP, polyester PET and polyamides PA 6.6 and PA 6 and polyvinyl chloride PVC are also used, the letter, however, only to a small extent...

The abrasion resistance is particularly important in the surf environment where coarse angular sand, shell fragments, or coral debris are present. The larger thickness of nonwoven geotextiles and the ability of their structure to retain sand material... 

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