Microballoons

In a recent report (79), a 150—200 mg/cm Parylene C coating provided protection against moisture uptake by three-phase, polyimide, microballoons, and air, syntactic foams. In a previously reported coating of a similar foam, the stated purpose was strengthening (80). 

Fiber-Optic Pins. In one version of the fiber-optic pin (Benjamin et al., 1984), a small microballoon, 0.25 mm in diameter, filled with a noble gas such as argon or xenon is attached to the end of an optical fiber. When the pin is impacted, the shock heats the gas in the microballoon producing a flash which is channeled to a recording system via optical fibers. Some of the useful features of this pin are... 

Incorporation of hollow or expandable spheres of resin or of glass (microballoons). 

The galvanic cell studied (shown in Fig. 5.24) utilizes a highly porous solid electrolyte that is a eutectic composition of LiCl and KCl. This eutectic has a melt temperature of 352 °C and has been carefully studied in prior electrochemical studies. Such solid electrolytes are typical of thermal battery technology in which galvanic cells are inert until the electrolyte is melted. In the present case, shock compression activates the electrolyte by enhanced solid state reactivity and melting. The temperature resulting from the shock compression is controlled by experiments at various electrolyte densities, which were varied from 65% to 12.5% of solid density. The lower densities were achieved by use of microballoons which add little mass to the system but greatly decrease the density. 

Foam Density lb./ft.3 Glass Microballoons Epoxy Macroballoons Uniaxial Compressive Yield Strength, psi Hydrostatic Compressive Strength, psi Method of Preparation Resin System... 

Microballoons have the advantage of giving a well controlled addition of sensitiser and also improved stability on storage. They are however less effective than direct gas occlusions when measured at constant explosive density and therefore tend to have most use in conjunction with the soluble additives described below. 

Microbalances, 26 245 Microballoons, phenolic, 18 796, 797 Microbe genetic engineering, 72 470-484 future of, 12 482 gene technologies in, 72 470-475 host systems for gene expression, 72 475—480... 

Orlando, FI., 7th-llth May, 2000, paper 49 EXTRUSION OF CLOSED CELL VERY LOW DENSITY FLEXIBLE SYNTACTIC FOAMS USING METALLOCENE CATALYZED POLYOLEFINS AND THERMOPLASTIC MICROBALLOONS Trainer L J Beauregard D Orroth S Schott N Massachusetts,University (SPE)... 

A streak camera is set up with the slit parallel to the long axis of the Lucite rod a photograph like that shown in Fig. 5-12(B) is obtained. This yields the shock velocity and the free surface velocity on the same photograph. In later work it was found that a coating of paint filled with microballoons (very tiny, hollow plastic spheres) could be substituted for the argon-filled gap with equal effect. 

Abstract— The use of organosilanes as adhesion promoters for surface coatings, adhesives and syntactic foams is described and reviewed in the light of published work. Data are presented on the beneficial effect of silanes, when used as pretreatment primers and additives, on the bond strength of two pack epoxide and polyurethane paints applied to aluminium and mild steel. It is shown that silanes when used as additives to structural epoxide and polyurethane adhesives are less effective than when used as pretreatment primers on metals but are highly effective on glass substrates. The compressive properties of glass microballoon/epoxide syntactic foams are shown to be markedly improved by the addition of silanes. 

Reference to Table 14 will show the effect of increasing levels of APES on the compressive properties of an anhydride cured epoxide/silica microballoon foam, the APES being added on the resin content. The notation w/r (wt% resin) has been used in the tables. Both the yield stress and strain to failure increased steadily with increased silane content, with a corresponding increase in compressive modulus. At the 5 wt% level there was no real increase in yield stress but a marked increase in strain to failure, resulting in a lower modulus. However, at the 4% level the compressive strength was more than double that of the nonsilane control. 

Effect of silane addition level on the compressive properties of an anhydride cured epoxide silica microballoon syntactic foam (APES, cured at 100 C for 4 h, nominal density 0.35 g/cm )... 

Figure 6. The effect of APES addition at increasing wt% on the stress/strain behaviour of an MNA/ Epikote 828/glass microballoon syntactic foam.

Syntactic foamed plastics (from the Greek ovvxa C, to put together) or spheroplastics are a special kind of gas filled polymeric material. They consist of a polymer matrix, called the binder, and a filler of hollow spherical particles, called microspheres, microcapsules, or microballoons, distributed within the binder. Expoxy and phenolic resins, polyesters, silicones, polyurethanes, and several other polymers and oligomers are used as binders, while the fillers have been made of glass, carbon, metal, ceramics, polymers, and resins. The foamed plastic is formed by the microcapsular method, i.e. the gas-filled particles are inserted into the polymer binder1,2). 

Sato, Y., et al. 2004. In vitro and in vivo evaluation of riboflavin-containing microballoons for a floating controlled drug delivery system in healthy humans. Int J Pharm 275 97. 

Property Calcium carbonate Kaolin Talc Mica Glass microballoons Hydrous alumina Silica Wood flour... 

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