Other fibers

Numerous fibrous products are used as fillers in plastics materials. Fibers are generally divided into natural and man-made fibers. The natural fibers belong to three groups vegetable, animal, and mineral fibers. Natural mineral fibers were 

Current research indicates that there is a growing interest in natural fibers. Natural fibers Ifom jute were tested in thermosetting and thermoplastic resins. Lignin fillers were used in phenol-formaldehyde, SBR, SBS, and S1S ° and with good results. The opportunities for applications of natural fibers in industrial products have been the subject of recent reviews. Cellulose whiskers with a high reinforcing value were obtained from wheat straw. Wood fibers were found applicable to such diverse materials as polypropylene 

Metal fibers form another group of important materials due to the growing interest in conductive materials. Some of these fibers were discussed together with metal powders, flakes and metal coated minerals in Section 2.1.40. 

There is also an interest in application of synthetic fibers. Two directions are common surface modification and development of fibers with special morphology. The controlled composition of synthetic fibers gives opportunities to regulate their surface properties to meet specific requirements giving the product formulator new tools to make product improvement. Synthetic fibers can be produced in variety of shapes and sizes which can be tailored to specific applications in new products. Ultra small fibers, some hollow, with a wide variety of surface morphologies can be produced economically to meet specific requirements of a wide variety of high technology products. 

4 Aluminum-pigmented Coatings for Industrial Maintenance Applications. The Aluminum Association, Washington, 1996. 

---

Physical Properties. Relationships between fiber properties and their textile usefulness are in many cases quite obvious. Since fibers are frequently subjected to elevated temperatures, it is necessary that they have high melting or degradation points. It is also necessary that other fiber properties be relatively constant as a function of temperature over a useful temperature range. 

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination. 

The wet modulus of fibers at various temperatures influences the creasing and mussiness caused by laundering. Figure 6 shows the change with temperature of the wet modulus of acetate and triacetate, and compares them with a number of other fibers (2). Acetate, triacetate, and rayon behave quite similarly, with a lower sensitivity than acryUc. 

Physical Properties. Table 1 (2) shows that olefin fibers differ from other synthetic fibers in two important respects (/) olefin fibers have very low moisture absorption and thus excellent stain resistance and almost equal wet and dry properties, and (2) the low density of olefin fibers allows a much lighter weight product at a specified size or coverage. Thus one kilogram of polypropylene fiber can produce a fabric, carpet, etc, with much more fiber per unit area than a kilogram of most other fibers. 

Table 2. Thermal Properties of Olefins and Other Fiber-Forming Polymers...

PET is based on petroleum and the price of polyester fiber fluctuates with the price of -xylene and ethylene raw materials as well as with the energy costs for production. With the abiUty to interchange with other fibers, especially cotton iu cotton blends, the price of polyester is affected by the price and avadabihty of cotton as well as the supply and demand of polyester. 

AH synthetic fibers are produced as continuous filaments, either as yams or tows. Yams are fine enough to be woven or knitted direcdy, but caimot be intimately blended with other fibers on the principal conversion systems used for cotton or wool. For these processes, staple fibers, made by cutting the much larger tows into short lengths, are needed. Tows can also be stretch broken into sHvers or tops, which can then be drawn out and twisted into spun-yams. 

A significant advantage of the PLM is in the differentiation and recognition of various forms of the same chemical substance polymorphic forms, eg, brookite, mtile, and anatase, three forms of titanium dioxide calcite, aragonite and vaterite, all forms of calcium carbonate Eorms I, II, III, and IV of HMX (a high explosive), etc. This is an important appHcation because most elements and compounds possess different crystal forms with very different physical properties. PLM is the only instmment mandated by the U.S. Environmental Protection Agency (EPA) for the detection and identification of the six forms of asbestos (qv) and other fibers in bulk samples. 

Fibers. The principal type of phenoHc fiber is the novoloid fiber (98). The term novoloid designates a content of at least 85 wt % of a cross-linked novolak. Novoloid fibers are sold under the trademark Kynol, and Nippon Kynol and American Kynol are exclusive Hcensees. Novoloid fibers are made by acid-cataly2ed cross-linking of melt-spun novolak resin to form a fuUy cross-linked amorphous network. The fibers are infusible and insoluble, and possess physical and chemical properties that distinguish them from other fibers. AppHcations include a variety of flame- and chemical-resistant textiles and papers as weU as composites, gaskets, and friction materials. In addition, they are precursors for carbon fibers. 

To accommodate the various uses in 100% form and in blends, the tenacities and elongations of the nylon staple offerings range from 0.3 to 0.6 N /tex (3—7 g/den) and from 50 to 100% elongation. Most other fiber properties of nylon staple differ tittle from those of the continuous filament property characteristics of nylon-6 and nylon-6,6 are similar (see Polyamides, general). 

In addition to aerospace uses, sihca fibers can be twisted into sewing threads and yams for weaving into fabrics. These fabrics are used extensively for heat-resistant clothing, flame curtains for furnace openings, thermocouple protection, and electrical insulation. The cloth can also be used to encapsulate other fibers to produce flexible sheets. 

Table 3. Mechanical Properties of Silks and Other Fibers ...

Other Fiber Deformations. Deformations such as bending, torsion, shear, and compression are of practical importance in textile apphcations. Bending and twisting of yams, both influential in the development of bulk and stretch in filament yams, are also important in the production of staple yams. Bending characteristics are important in cmsh resistance in carpets. Bending and shear are factors that influence the hand and drape of apparel fabrics, whereas compression influences the recovery of fabrics after such processes as winding. 

Wool belongs to a family of proteins, the keratins, that also includes hair and other types of animal protective tissues such as horn, nails, feathers, and the outer skin layers. The relative importance of wool as a textile fiber has declined over the decades as synthetic fibers have increa singly been used in textile consumption. Wool is still an important fiber in the middle and upper price ranges of the textile market. It is also an extremely important export for several nations, notably AustraUa, New Zealand, South Africa, and Argentina and commands a price premium over most other fibers because of its outstanding natural properties of soft handle (the feel of the fabric), moisture absorption abiUties (and hence comfort), and superior drape (the way the fabric hangs) (see Fibers Textiles). Table 2 shows wool production and sheep numbers in the world s principal wool-producing countries. 

Other fiber classification schemes have been devised for chrysotile fibers, but historically the QS grade system has been used as a reference other classification schemes usually have correspondence scales for conversion to the QS values. Amosite can be classified according to the QS grade system, but crocidohte requkes a different scheme (mainly due to the harshness of these fibers). 

Other Fiber Evaluation Methods. The extent of fiber separation (fiber openness) is an important evaluation criteria that is commonly measured by several techniques, namely ak permeabiUty, adsorbed gas volume, bulk density, and residence (compression and recovery). The adsorption and retention of kerosene is also used as a measure of fiber openness and fiber adsorption capacity (34). 

The search for asbestos replacement materials is obviously an ongoing process and further developments in this area are to be expected. The extent of substitution of asbestos fibers by other fibers or other materials has been limited by several factors, typically the availabiHty of adequate replacement materials, the cost performance ratio of such materials, and the uncertainty of long-term health risks of these replacement materials. From the data currendy available, it may be estimated that between 10—20% of the industrial consumption of asbestos fibers was diverted to other materials during the 1980s. 

Asbestos and other fibers in a wide variety of bundle sizes or even individual fibrils are in commercial usage. The handling of asbestos and other fibers causes degradation of the larger fiber bundles to fibers having diameters less than two micrometers that remain airborne for extended periods of time. These airborne fibers are prone to inhalation and lung entrapment. The exact definition of harmfiil fibers and the mechanism by which they affect the body is not accurately known. 

Polyester fibers are based on poly(ethylene terephthalate) (PET) some modified versions are formed by copolymerization, eg, basic dyeable polyester. The modified forms dye in analogous manner to other fibers of similar charge. 

Other fibers blended with polyesters in numerous blended fabrics requke alternative methods of preparation. Generally, the scouring and bleaching procedures used for these blends are those employed for the primary component of the blended fiber or for the component that most influences aesthetic appearance. 

---