Definitions, Manufacture and Processing

The fibers are produced continuously (endless fibers, filaments) or discontinuously (short or staple fibers) depending upon the application. Most of the fibers are obtained by extruding a flowable form (melt or solution) of appropriate chemieal composition (Section 5.2.3 - 5.2.4). Other processes are based on deposition from the gas phase (Section 5.2.6.2) or thermal transformation (pyrolysis) of organic (Section 5.2.5) or organometallic polymers (Section 5.2.7). 

The fibers or the yarn or rovings made therefrom can be processed to fleeces or mats (non-oriented semi-finished product) and textiles, lattices or meshes (oriented semifinished products) and can be utilized as such e.g. for thermal insulation or as filter materials, or in composites with other materials e.g. for fiber-reinforced polymers, metals or ceramics. Fibers are generally marketed after surface treatment (chemical modification, annealing, smoothing) to optimize their application and processing properties. 

Worldwide production of fibers was c t. 45 10 t/a in 1993, of which ca. 20% was inorganic fibers. Whereas at the turn of the twentieth century the fibers utilized were almost exclusively natural fibers (organic fibers cotton, sheep s wool and silk inorganic fibers asbestos), by 1993 the proportion of synthetic fibers had grown to ca. 50%. This trend appears to parallel the increasing world population and the consumer behavior coupled therewith. 

By far the most important application fields for inorganic fibers are the insulation and reinforcing sectors. Fibers are also used as fillers and as filter materials. As with other materials, functional properties such as electrical, optical or magnetic properties are becoming increasingly important for fibers, in addition to mechanical and electrical properties. 

In the reinforcement sector a number of fibers are available, which differ considerably both in price and also in chemical and thermal stability. This has a direct impact on their suitability for the production of fiber composites. Finally there are multiphase materials, in which reinforcing fibers are embedded in the form of short or endless oriented or non-oriented fibers, in a polymeric, metal or ceramic matrix. 

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