Impregnation asbestos

In 1968 the Monsanto Company announced the availability of novel soluble low molecular weight polyphenylene resins. These may be used to impregnate asbestos or carbon fibre and then cross-linked to produce heat-resistant laminates. The basic patent (BP 1037111) indicates that these resins are prepared by heating aromatic sulphonyl halides (e.g. benzene-1,3-disulphonyl dichloride) with aromatic compounds having replaceable nuclear hydrogen (e.g. bisphenoxy-benzenes, sexiphenyl and diphenyl ether). Copper halides are effective catalysts. The molecular weight is limited initially by a deficiency in one component. This is added later with further catalyst to cure the polymer. 

Table 5 lists the seven Venera and Vega space probes that made elemental analyses of the surface of Venus. In addition to elemental analyses, several of the Venera and Vega landers measured density, bearing capacity, electrical resistivity, and atmospheric redox state (via the reaction of chemically impregnated asbestos with atmospheric CO). The Venera 8-10, and Vega 1-2 probes analyzed... 

Equipment for impregnating asbestos is conceptually similar to those used for glass cloth coating. Asbestos readily picks up PTFE dispersions and the amount of uptake depends on the concentration of PTFE in the dip tank. The dispersion may be diluted moderately with deionized water or substantially using a dilute aqueous solution of a nonionic surfactant such as Triton X-100. The speed of the asbestos yam movement through the dip tank has little effect on the amount of uptake. The length and capacity of the oven determines the maximum throughput of the process. 

Fig. 1. Load decay curve. Sample fluorocarbon oil impregnated asbestos and rubber.

Zinc spraying of plastics or phenolic-impregnated asbestos is used to provide reflecting surfaces, and the large open-air dishes used in electronic applications are so coated. In impressed current protection of rebar in concrete, the exterior of the concrete is sometimes zinc sprayed (Morrow, 1991) to give a uniform current distribution (see subsection on impressed current systems in Section II. E) in such cases, it is often policy to avoid direct electrical connection between zinc and rebar, since the consequent use of zinc as a sacrificial anode could be counterproductive if only a limited amount of zinc is present to protect large areas of steel. 

The possible introduction of plastics brake pedals is discussed in Chapter 4. This possibility could be said to represent the ultimate intrusion of plastics into brakes technology. The intrusion in fact started as early as the First World War, when PF resin was first used to impregnate asbestos brake linings. 

Crucial components in attaching the copper sheets to the armature were the copper saddles, depicted in Fig. 5.12. These U-shaped components wrapped around the armature iron bars and were riveted to the copper skin. Some 1500 of these copper saddles were used. During construction in the United States, shellac-impregnated asbestos was placed between the armature and the skin, but this disintegrated with time and, through wicking action, acted as an undesirable trap... 

BASF Platinized asbestos produced by impregnating asbestos with platinic chloride solution followed by reduction with formaldehyde. Operated up to 10-12 years in several 10 20 cm layers. Contained 8-10% platinum. Tubular reactors were still designed for vanadium catalysts until 1950s. Agreement with Grillo up to 1898. 

V. Kosi, Some properties of poly (methyl methacrylate) impregnated asbestos-cement... 

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