Semifinished fiber products

In all processes, the feeding time of the cavity can be significantly reduced by using assembied semifinished fiber products (preforms). This increases the economic feasibiiity for the manufacture of components with complex spatial structure. 

The thermoplastic semifinished part production can be divided into the following processes impregnating, consolidating, and transitioning to the solid state. During processing, the input materials (fiber and matrix) depend on the process-required control variables Temperature T, time t, and pressure p, which will then determine the resulting properties of the semifinished parts [2]. 

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. 

The qualitative importance of the CPI to the U.S. economy lies mainly in its contribution of synthetic materials and semifinished materials for further processing and manufacturing. It has been exceedingly successful in displacing natural products. Consider the replacement of natural dyes with synthetic dyes cotton, wool, and silk with synthetic fibers herbal and natural medicines with antibiotics smoky coal with cleaner burning oil and clean-burning natural gas, and many other examples. The CPI has been a major contributor to every sector of human need. Table 8.36 is a partial list of the many contributions to society by the CPI. 

Impregnation with PP is done on a double belt press that consolidates the fibers with PP under the influence of pressure and temperature. After the composites cool, the GMT semifinished product can be cut for specific applications. 

Flexibility in terms of variations in material combinations in structural components is also severely limited by use of semifinished products. Large volumes of the same material combination are produced to ensure economical production of the semifinished products. There is thus no application-specific modification or stabilization of the material and the glass fiber content cannot be adapted specifically to the mechanical requirements of the structural components. These are the reasons why semifinished products are available in a limited number of material variants only. 

Processes for production of rubber semifinished products by means of spreading Processes for production of rubber composites and stmctural elements (yams, cord, fibers, threads) and mbber-metal composites. 

So-called direct processes (LFT-D) are increasingly becoming established in the market, i.e., processes in which the parts are molded directly from the components glass fibers, polymers and additives by the extrusion method, thus circumventing the semifinished production step entirely. 

Table 22.1 compares properties of conventional reinforcing fibers, self-reinforced polypropylene fibers and compact polypropylene semifinished products, which are described in literature. 

The films and fibers are then both processed into the previously discussed semifinished products by means of conventional textile processing methods. Filament yams, woven fabrics and unidirectional fabrics, but also endless fiber fleeces and staple fiber fleeces, can be made from the fibers [40]. The films can be employed as semifinished products directly after being mono-, bi- or (rarely) multiaxially stretched. For the most part, the fibers are tailored into tapes, monoaxially stretched and woven into oriented textile products in order to produce the essentially woven fabrics. 

The technicaiiy reievant properties of poiymers, such as shapabiiity, hardness, eiasticity, tensiie strength, temperature, and chemicai resistance can be varied over a wide range by the seiection of raw materiais, manufacturing methods, and choice of additives. Poiymers are processed further to become moided parts, semifinished products, fibers, or Aims. 

With only 1 L of the dispersion it is possible to coat about 100 m of the surface of various semifinished or finished products such as films, fibers, panels, sections, textiles, and paper, made of a wide variety of materials. There may be differences in bonding strength and abrasion resistance. Abrasion resistance on PC, PET copolymers, and ABS is good, whereas on PET homopolymers, PVC, PE, or aluminum it has to be described as moderate. 

It has to be mentioned, however, that this way of textile manufacturing of semifinished products is not a real 3-D process because it produces only spherically formed two-dimensional reinforcement geometry (fabric). There are no reinforcement fibers in the vertical direction of the body s surface. 

---