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P
polyamide (PA)
Thermoplastic with a density of approx. 1.14 g/cm_. Loses by means of water absorption approx. 10 % of its strength. Polyamide is hardly used due to high raw material costs.
polyester (PET)
Thermoplastic with good chemical resistance, except in alkaline surroundings (pH > 9). Due to the high density of 1.38 g/cm_, PET is used among others for nonwoven fabrics in hydraulic engineering. Due to high strength properties and low creep behaviour, PET is also used for reinforcement applications.
polyethylene (PE)
Thermoplastic with excellent chemical resistance. In the field of geosynthetics, mostly high density polyethylene (HDPE) and low density polyethylene (LDPE) are used.
polymer
See synthetic raw material
polypropylene (PP)
Thermoplastic with very good chemical resistance and a density of approx. 0.91 g/cm_. Geosynthetics from PP are used in nearly all fields of application.
polyvinyl chloride (PVC)
Thermoplastic made flexible by the use of softening agents and having a density of approx. 1.38 g/cm_. Mostly used as geomembrane where flexible liners are required. Because of the washing out of softening agents, the long-term resistance has to be examined with regard to the project specifications.
profiled surface
Surface of a geomembrane which is formed out of the geomembrane sheet during the manufacturing process by means of profiled calender drums. Hence the profiled structure and the geomembrane are homogeneous and consist of the same raw material.
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R
rod
See monofilament
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S
sand rough surface
Surface of a geomembrane which is textured and where the texturing is sprayed on the surface fibrelike while the bond between the structure and the geomembrane is significantly lower than the strength of the geomembrane. Sometimes the raw materials of the structure and the geomembrane differ due to manufacture.
slit film
Cut stripes of foil which are used in wovens as tensile element.
smooth surface
Surface of a geomembrane which is smooth and does not have any texturing (sand rough or textured) or profile.
sodium bentonite
See natural sodium bentonite
staple fibre
Short fibres obtained by cutting filaments which are additionally crimped. In mechanically bonded nonwovens, this three-dimensional crimping can improve among others the abrasion resistance and the friction behaviour.
stitch-bonded geosynthetic clay liner
(Yarns) threads are passed through the cover geotextile, bentonite layer and carrier geotextile securing a composite product by creating a directional orientation. Therefore, the direction of shear transfer is predetermined.
strand
An orderly assemblage of .
synthetic raw material
Chemically produced material for the production of geosynthetics. Polypropylene (PP), polyethylene (PE), polyester (PET), polyvinyl chloride (PVC) and/or polyamide (PA) are mainly used for geosynthetics.
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T
tex
A weight-per-unit-length measure (fineness) of a yarn, filament, fibre, or other textile strand for expressing the mass in grams of 1,000 m.
textured surface
Surface of a geomembrane which is textured and in which the texturing is caused by means of bursting gas bubbles in a thinner outer skin.
thermally bonded nonwoven
By adding melting fibres, by melting the fibre surface or by means of heat calenders (drums), fibre crossing points are thermally bonded with each other. The most usual type of production is hot-calendering. This causes relatively thin, hardly robust and rarely filter stable nonwovens. The thermal melting of the fibre crossing points makes thermally bonded nonwoven fabrics rigid (low elongation) and thus more susceptible to installation damage.
thermoplastic
A term used to describe a plastic material that is permanently fusible. Well-known thermoplastics are polypropylene, polyethylene, polyester, polyvinyl chloride and polyamide.
thermoplastic geomembrane
Homogeneous geomembrane manufactured with synthetics, with a minimum thickness of 1.0 mm. In German landfill engineering, nearly exclusively BAM certified HDPE geomembranes (thickness > 2.5 mm) are used for sealing applications due to their high chemical resistance. In groundwater protection, usually DIBt certified products are used in Germany. The surface may be smooth, profiled, structured or sand rough and is important for the friction behaviour.
thread
A strand, cord or bundle, designed for sewing or needlework by plying and twisting yarns.
twist
See strand
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