Silicone vacuum fluid

Estapol, a blend of polyester/polyether resins NA, not available PBA, polybutyl acrylate PUV, polyurethane varnish PVAL, polyvinylalcohol SVF, silicone vacuum fluid fiber volume fraetion. 

Fig. 7,2. Fracture toughness, R, of Kevlar 49-epoxy matrix composites (a) under varying strain rates in three-point bending and (b) at different temperatures under impact loading (O) uncoated fibers (0)41%, (Q) 63% and ( ) 100% Estapol coated fibers (A) silicone vacuum fluid (SVF) coated fibers. After Mai...

Fig. 7.3. Normalized impact toughness of glass fiber-polyester matrix composites with different fiber coatings (O) silicone vacuum fluid (SVF) Dow Coming 200 Fluid of viscosity 10 cP (A) Dow Corning 200 Fluid of viscosity 10 cP. After Sung et al. (1977).

Silicone vacuum pump fluids are used in the diffusion pumps which provide high vacua for the production of semiconductors and cathode ray tubes or other vacuum devices. 

In contrast to many other surface analytical techniques, like e. g. scanning electron microscopy, AFM does not require vacuum. Therefore, it can be operated under ambient conditions which enables direct observation of processes at solid-gas and solid-liquid interfaces. The latter can be accomplished by means of a liquid cell which is schematically shown in Fig. 5.6. The cell is formed by the sample at the bottom, a glass cover - holding the cantilever - at the top, and a silicone o-ring seal between. Studies with such a liquid cell can also be performed under potential control which opens up valuable opportunities for electrochemistry [5.11, 5.12]. Moreover, imaging under liquids opens up the possibility to protect sensitive surfaces by in-situ preparation and imaging under an inert fluid [5.13]. 

The fluids used in oil diffusion pumps are usually hydrocarbon esters (e.g., Ai n octylphthalate) that are heated to 130 to 160°C in operation or silicone or polyphenyl ether fluids that operate at higher temperatures (180 to 280°C). The latter fluids are quite expensive but give lower ultimate vacuum levels (10 to 10 ° Torr) and greater resistance to oxidation by excessive amounts of air. Further information is given in Table 1. Warning When hot, a diffusion pump should never be exposed to pressures above about 0.1 Torr never vent an oil diffusion pump to air when it is hot. 

Modem diffusion pumps use special silicon oils or other stable compounds as the work fluid instead of a mineral oil. A heater causes the oil to boil and to vapourize in a flue. The oil vapour emerges from nozzles such that the vapour issue is directed away from the high vacuum side. During the exhaust from the nozzles, the vapour... 

After addition of water, the oil is separated from the aqueous acid layer and neutralized. To produce nonvolatile silicone fluids, volatile low-molecular products are removed by using a vacuum still. Commercial nonvolatile fluids have a weight loss of less than 0.5% after 24 h at 150°C. 

After hand lay-up, winding, or other fabrication technique, mold and composite part are placed in an autoclave. Heat and pressure are a lied via steam, consolidating and curing part. Usually combined with a vacuum-bag bleeder and release cloth. Hydroclave uses water as the pressure media. Thermoclave process uses powdered silicone rubber which acts as a fluid under heat/pressure. 

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