Polymer fibers

from Wikipedia, the free encyclopedia

Polymer fibers ( poly (Greek) = many, meros (Greek) = particles) are organic fibers, the fiber material of which consists macrotectonically of molecules that are linked to one another through main valence bonds to form macromolecules (= polymers). One differentiates:

  • from given polymers: natural polymer fiber, such as B. cellulose fiber, protein fiber, rubber fiber, alginate fiber,
  • from created polymers: synthetic fiber.

Basics

Polymers can be classified according to the number of basic materials ( monomers ) from which they are made. However, it is important that at least one monomeric substance builds the chain. With the exception of glass and metal fibers, most fibers and especially polymer fibers, viewed microscopically, consist of a composite of tiny fiber bundles.

A distinction is made between

The diameter of the fibers varies between 1 µm and 100 µm.

With the exception of aramid and polyethylene fibers, no polymer fibers are used for fiber composite materials . Polymer fibers are mainly used as the basic material for the membrane structure, since the excellent flexibility and elasticity of the materials is decisive there.

Determination of mass and key figures

The length-related mass of the polymer fibers is determined - as with other fiber types - in dtex , with 1 dtex corresponding to the value of 1 g / 10 km.

Polymer fibers used today preferably have a processed very low density of 0.01 kg / l to 0.1 kg / l. Polyester itself, however, has a density of 1.24 kg / l.

Another key figure that specifically characterizes microphysics is the degree of polymerization .

Manufacturing

The starting point for the production of polymer fibers are plastic flakes or granulates, e.g. made of PET , which are further processed into thin fibers by drying, subsequent melt extrusion and other downstream process steps. The extruded polymer is filtered before it passes through the spinning mill, where it is spun into a thread . In the further manufacturing process, the spun threads are drawn, dried, cut into staple fibers and processed into bales.

A bale opener is used to remove fiber clumps from the pressed bales. The fibers are detached mechanically . For the production of polymer fiber filters, for example, it is necessary to mix larger quantities of fibers. This is the only way to balance out differences in terms of cleanliness, color, fineness, firmness and concentration. The final operational readiness is then achieved through further downstream work steps.

Use in filtration

Filtration generally refers to a mechanical separation process for separating solids from a fluid. The fluid, which contains the solid particles, flows through a filter material. The latter holds back the solid particles depending on its selectivity. Depending on the separation task, the effect of the filter is based on different separation mechanisms .

The use of polymers and in particular of polyester has recently proven its worth due to their particular suitability for the filtration of liquids and aqueous suspensions . Polymer fibers that are used for filtration are not filaments (fibers with unlimited length), but rather defined finite fibers with a typical length in the range from 10 mm to 200 mm. Also comes u. a. the advantageous dynamic fixation of the fibers for use. Furthermore, strength, frictional connection and form-locking connection of the fibers are used. The fiber's own adhesion is reinforced by a mechanical treatment, whereby the material strength can be increased in a targeted manner. The focus is on a cohesive instead of an adhesive bond.

Since the distances between the individual fibers are significantly greater than the fiber and particle diameter, fiber filters are an open material with high porosity. This means they can be used for deep filtration . In contrast to surface filtration, this process ideally does not produce a filter cake .

disposal

When disposing of used polymer fiber products, the legal requirements must be followed. Depending on the substance to be separated, this can mean returning it to a recycling process, but also disposal as hazardous waste.

literature

  • Jan Knippers, Jan Cremers, Markus Gabler, Lienhard Julian: Atlas Kunststoffe + Membranen. Munich u. a. 2010, ISBN 978-3-920034-41-6 .
  • Horst Gasper, Dietmar Oechsle, Elmar Pongratz: Manual of industrial solid / liquid filtration. 2nd Edition. Weinheim 2000, ISBN 3-527-29796-0 .
  • Peter Grombach, Klaus Haberer, Gerhard Merkl, Ernst U. Trüeb: Handbook of water supply technology. 3. completely revised. Edition. Munich u. a. 2000, ISBN 3-8356-6394-1 .
  • Li, Shen, Ernst Worrell, Martin K. Patel: Comparing life cycle energy and GHG emissions of bio-based PET, recycled PET, PLA, and man-made cellulosics. In: Biofuels, Bioproducts and Biorefining. Vol. 6, No. 6, 2012, pp. 625-639.

Individual evidence

  1. ↑ Günter Schnegelsberg: Manual of the fiber - theory and systematics of the fiber . Deutscher Fachverlag, Frankfurt am Main, 1999, ISBN 3-87150-624-9 ; P. 586.
  2. ↑ VDI 3469 sheet 1: 2016-09 emission reduction; Manufacture and processing of fibrous materials; Fibrous dusts; Basics, overview (Emission control; Production and processing of fibrous materials; Fibrous dusts; Fundamentals, overview). Beuth Verlag, Berlin. P. 7.
  3. ↑ VDI 3677 sheet 1: 2010-11 Filtering separators; Surface filters (Filtering separators; Surface filters) . Beuth Verlag, Berlin. P. 13.
  4. ↑ VDI 3677 sheet 1: 2010-11 Filtering separators; Surface filters (Filtering separators; Surface filters) . Beuth Verlag, Berlin. P. 6.
  5. ↑ VDI 3677 sheet 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin, p. 12
  6. ↑ VDI 3677 sheet 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin, p. 70.