Mineral and Metallic Fibers

Often fibers in textile substrates are deficient in one or more properties, or improved properties are desired for the substrate. Textile finishing provides a method whereby deficiencies in the textile can be corrected or specific properties can be introduced. Physical finishing techniques (dry finishing processes) or chemical finishing methods (wet finishing) are used. Physical finishing is usually carried out on the yarn or formed textile substrate, whereas chemical finishes can be added to the spinning bath prior to fiber formation for man-made fibers or appl ied to individual fibers, yarns, or completed textile structures. 

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Mineral and Metallic Fibers G1 ass Inorganic Asbestos Metallic... 

A limited number of finishes are used on mineral and metallic fibers. Glass fibers are often surface treated with agents such as chromium salts or silanes to improve their ability to adhere to organic adhesive materials used in polymer-glass fiber composites. Various organic starches, proteins, and synthetic polymer sizings are applied to glass fabrics to protect the individual fibers and to lower abrasion between individual fibers. 

If individual controllers are used instead of optimal computer control, several strategies are possible. In one strategy (Lynch and Fiber, 3rd IFAC Symposium on Automation of Mining, Mineral and Metal Proce.ssing, 25-32, 1980) the sluri y-pump rate is controlled to maintain sump-level constant, which results in smooth cyclone operation. The water-feed rate is ratioed to the ore-feed rate, which keeps the circiilating load from oscillating. The ore-feed rate is then controlled to maintain product-particle size. 

There are several major areas of interfacial phenomena to which infrared spectroscopy has been applied that are not treated extensively in this volume. Most of these areas have established bodies of literature of their own. In many of these areas, the replacement of dispersive spectrometers by FT instruments has resulted in continued improvement in sensitivity, and in the interpretation of phenomena at the molecular level. Among these areas are the characterization of polymer surfaces with ATR (127-129) and diffuse reflectance (130) sampling techniques transmission IR studies of the surfaces of powdered samples with adsorbed gases (131-136) alumina(137.138). silica (139). and catalyst (140) surfaces diffuse reflectance studies of organo- modified mineral and glass fiber surfaces (141-143) metal overlayer enhanced ATR (144) and spectroelectrochemistry (145-149). 

For example, brake linings contain finely divided, hard, abrasion resistant particles (Tab. 11-1, Chapter 11) in a complex matrix that provides the bonding in the lining itself and with the metallic supports. The formulation, containing all components, may also include such materials as metallic, mineral and, synthetic fibers. During production of the break drums, discs, or shoes, the blend is pressed onto the structural supports with specially designed presses to produce uniform, homogeneous wear pads. 

PACKING - Material made usually of woven animal, plant, mineral or metal fiber and some type of lubricant, placed in rings around the shaft of a pump and used to control leakage from the stuffing box. 

Mineral, organic and metallic fibers, and the surfaced materials made from them such as fleece mats, textiles, and weaves, not only make possible economical manufacturing of materials with specifically targeted physical property improvements based on standard plastics and technical molding compounds, but also help manage high mechanical stress loads, which are often direction-dependent and show local variations, with anisotropic composite structures. 

For reasons related to industrial safety and environmental protection, considerable effort has been invested for decades now in replacing asbestos in such items as automobile brake and clutch plate linings with metal, glass, synthetic mineral and organic fiber materials. Asbestos-free disk brakes and clutch linings have now been on the market, and on original equipment lines, for some time. The phenolic resin... 

The diverse shapes of inclusions may be used for a classification of composites, as shown for the basic cases of particulate, fibrous, and lamellar topologies in Figure 5.1. There are also composites which represent a combination of these inclusion types. In steel concrete, for example, mineral particles and metal fibers are joined by a binder material. For aerospace applications, the... 

For friction material appHcations, composite materials (qv) comprising glass or metallic fibers with other minerals have been developed. In such appHcations also, aramid and graphite fibers are effective, although the cost of these materials restricts their use to heavy duty or high technology appHcations (see Carbon fibers). 

Nonfibrous Reinforcements. Because of the higher costs associated with nonasbestos fibers and the performance requirements needed in replacing asbestos, platy minerals such as mica and talc, and metal powders such as iron and copper, are being used as a portion of the total reinforcement package in NAOs. 

Many dyes that have no chemical affinity to fibrous substrates can be attached to such substrates by intermediary (go-between) substances known as mordants. These are either inorganic or organic substances that react chemically with the fibers as well as with the dyes and thus link the dyes to the fibers. Mordants are traditionally classified into two main classes, acid and metallic mordants. The acid mordants are organic substances that contain tannins (see Textbox 64) as for example, gall nuts and sumac. The metallic mordants are inorganic substances, mostly mineral oxides and salts that include metal atoms in their composition. Table 94 lists mordants of both these types, which have been used since antiquity. 

The high frictional coefficient (0.4 to 0.5 compared with < 0.1 for glass fibers) of asbestos fibers is crucial to its utilization in the frictional lining sector. In the manufacture of brake and clutch linings 20 to 60% asbestos is incorporated together with fillers, metal chips and preferably phenol resins and rubber into a composite material, which has to satisfy many requirements. Currently there are asbestos-free so-called semimetallic brake linings, which consist of mixtures of metal fibers, metal powders, cellulose fibers, aluminum silicate fibers and mineral wool bonded with synthetic resins. 

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. 

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