Manufacturing of geotextiles

Heatbonded nonwoven made of continuous filaments (usually spunbonded)  

The classic geotextiles are fabricated in two steps, i.e. the production of fibres, filaments, slit films (tapes), or yams followed by converting these constituent materials into a fabric. The constituent materials required for the manufacture of geotextiles are produced using various techniques, as discussed below.  

Short (staple) fibres. Filaments are chopped into short lengths ranging from 2 to 10 cm, which are known as staple fibres. These staple fibres are then twisted together to form a yam. 

Slit films. The films are produced through a melt extrasion process using slit dies which are subsequently slit with sharp blades. These films can be further fibrillated and broken into fibrous strands, known as a fibrillated yam. 

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There are several different processes and polymers used ia the manufacture of geotextiles which affect their appearance and physical properties. Geotextiles are produced ia various weights and thicknesses, which also determine their physical properties and ultimately the performance of the material when iastaHed on a project (see also high performance fibers). 

Both natural and synthetic fibres are used in the manufacture of geotextiles. Natural fibres can be classified based upon their origin, whether plant or vegetable, animal, or mineral. Plant fibres have the greatest potential for use in geotextiles because of their... 

Similarly, the nse of recycled polymers for the manufacture of geotextiles also affects their long-term dnrability. The recycled fibres are often of mixed type and therefore the geotextiles produced from these fibres may not have the same performance and consistency as those of the virgin material-based geotextiles. Therefore, it must be noted that the chemical and mechanical durability characteristics of geotextiles should be considered while designing these materials for the required applications. 

Natural fibers and the majority of regenerated fibers are seldom used to make geotextiles and geomembranes because they are biodegradable. Because of ease of manufacture, useful properties, and general economy, the most common synthetic fibers used in the manufacture of geotextiles are polypropylene (PP), polyethylene (PE), polyester (PET) and polyamide (PA). 

Considering that geotextile production is increasingly taking on an international scale beyond national boundaries, one can believe that the quest for performance, cost reduction and increased productivity will drive future developments and investments in this industry in years to come. Continuous improvement processes, value-added products and cost reduction should stimulate the manufacturers of geotextile products and of geotextile equipment. Reduction in down time and maintenance time are also opportunities to reduce the costs identified by manufacturers. Improved quality and process control techniques such as automatic product inspection, use of electronic servo-systems and implementation of statistical process control techniques should also continue to advance in the geotextile industry. 

Nonwoven geotextiles. Nonwoven fabrics are defined as a sheet, web, or batt of directionally or randomly oriented fibres/filaments, bonded either by friction, and/or cohesion, and/or adhesion. In general, nonwoven fabric formation can be considered as a two-step process web formation (aligning the fibres with certain orientation characteristics) and bonding these fibres by mechanical, thermal, or chemical means. This two-step process has formed the classification of nonwoven structures, i.e. carded, airlaid, spunlaid, meltblown, needlepunched, hydroentangled, adhesive bonded, thermal bonded, stitch bonded, etc. Some of the important processes that are used for the manufacture of nonwoven geotextiles are discussed below. 

The manufacturing of special geotextiles is also briefly discussed below. 

Within the European Union (EU),the Construction Products Directive -89/106/EEC has resulted in minimum standard test requirements for any geotextile that is to be utilised for the possible functions described above. These are referred to as the CE marking requirements. All manufacturers of building and construction products in the EU are required to comply with the CE marking requirements and provide the appropriate test certificates. This became mandatory for geotextiles in October 2002. The CE mark is therefore seen as a guarantee that, for application of a particular functionaUty, the properties of a product will match those claimed by its manufacturer. 

Nonwoven fabrics have played an important part in the development of geotextile applications. Needle-punch fabrics manufactured from either staple fibers or spunbonded continuous filaments have found worldwide acceptance on the basis of field performance. In 2000, it is estimated that North America consumed approximately 300 million m of geotextiles (62). 

These limitations and the urgent necessity for both users and manufacturers to predict lifetime of geotextiles have led to the development of accelerated tests which... 

The PET industry is constantly searching for new applications for reclaimed material and there are many developing markets for rPET. Polyurethane foams can be manufactured as a result of the polyester polyols developed from rPET flakes. Engineered resins made from recovered PET can be injection moulded to manufacture computer and automotive parts. Other alternative production processes use spun-bonded PET in the manufacture of shoe liners, webbing and geotextiles (shoes, backpacks) [11]. 

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