Silicones Silastic

In an effort to optimize the solvent-containing passive sampler design, Zabik (1988) and Huckins (1988) evaluated the organic contaminant permeability and solvent compatibility of several candidate nonporous polymeric membranes (Huckins et al., 2002a). The membranes included LDPE, polypropylene (PP), polyvinyl chloride, polyacetate, and silicone, specifically medical grade silicone (silastic). Solvents used were hexane, ethyl acetate, dichloromethane, isooctane, etc. With the exception of silastic, membranes were <120- um thick. Because silicone has the greatest free volume of all the nonporous polymers, thicker membranes were used. Although there are a number of definitions of polymer free volume based on various mathematical treatments of the diffusion process, free volume can be viewed as the free space within the polymer matrix available for solute diffusion. 

Petty and Orazio (1996) developed an interesting variation in SPMD liquid phases. The approach consisted of both LDPE and silastic ffibes containing silicone fluid (50 cSt or 3200 MW) with 3% by weight PX-21 activated carbon. The presence of the activated carbon enhanced retention of planar molecules such as PAHs and the silicone fluid remains liquid at temperatures below freezing. However, the partition coefficients of HOCs for this type of silicone fluid are much lower than for triolein. 

Huckins, J.N. and Petty, J.D.1994a, Use of medical-grade silicone or silastic mbing alone as apassive sampler medium. USGS, Columbia Environmental Research Center, Colrrmbia, MO Unpublished work. 

Such a fluoroalkene, prepared for the first time by Haszeldine [283] by dehydro-iodination of F3CCH2CH2I, is the original precursor of commercially available fluorinated silicone from Dow Corning, called Silastic (see Sect. 7.2). Such a polymer preserves interesting properties (inertness, fair surface tension, chain mobility) at low and rather high temperatures. 

Three series of products are used as lubricants silicone-oils or polytrifluoro-propyl methyl siloxane (Silastic 15-53 produced by the Dow Corning Company), perfluorinated polyethers (Fomblin, Montedison now Ausimont Company) and Kel F oils (3 M Company). Only these latter ones are obtained directly by telomerisation. 

Ethyl p-aminobenzoate was used as the test compound for determining release characteristics. It was suspended in silicone elastomer base (Dow Corning Silastic, type 382). After the benzoate was thoroughly dispersed in the elastomer, the catalyst was added and the voids in the device were immediately filled. When cured, excess rubber was trimmed off so that the bottoms of the cells were flush with the lower surface of the device. 

Due to the liquid state of the silicone prepolymer, silicone polymers are prepared as preformed sheets and tubing or any other shape by first mixing the drug with the silicone polymer and a catalyst (e.g., stannous octoate). Then, the mixture is cast as a sheet or in a mold followed by curing overnight. For example, Norplant is a set of flexible, closed cylindrical capsules (2.4 x 34 mm) of Silastic silicone polymer containing levonorgestrel for fertility control for 5 years. The capsules are inserted under the skin of the upper arm. 

Figure 4.2 Structure of silicones (a) silicone fluid (Dow Coming 360 Medical Fluid) (b) silicone foam elastomer (c) silicone elastomer (vulcanized Silastic 382 Medicalgrade Elastomer) and (d) silicone elastomer (vulcanized Silastic Medical Adhesive Type A)...

Silicone mbber, especially poly dimethyl siloxane (Silastic) Silicone-carbonate copolymers, Surface-treated silicone mbbers Poly (ethylene-vinyl acetate), Polyethylene, Polyurethane (Walopur)... 

Liquid Silicone Rubber Silastic Silastic Q3-9590 Q3-9595 High Consistency Silicone Rubber Silastic 4515U... 

Cannulas are made of silicon rubber. The proximal bile cannula, which will be inserted into the common bile duct in the direction to the liver, is 18 cm long (Silastic tubing, Dow Coming, no. 605-135 0.51 i.d. and 0.94 o.d.) and has one square cut and one bevelled end. Two silicon rings are wrapped around the cannula at 7 mm and 50 mm, respectively, from the bevelled end. 

Mullison, E. G., Silastic Silicone Rubber with Steroids used in Contra-... 

The probe (Figure 14) is made of two copper constantan thermocouples connected so that the difference in the emf generated between them can be measured, and is very similar to Palmer s system. One thermocouple was left bare, and the other embedded in silicone rubber (silastic). The probe output was read using a digital voltmeter. 

Strong, topical corticosteroids should be applied, twice daily, very locally. A self-adherent silicone dressing (Silastic or Mepiform /Mepitel Figure 37.44) should be worn 24 hours a day that adapts to the curves of the skin and does not pull away growing cells when the dressing is changed. 

Silastic . [Dow Coming Dow Coming France SA] Silicone rubber conqxl. for conq>r., transfer, or inj. molding, calendering, extrusion, and blending. 

Many of the silicone elastomers that are used in biomedical applications are produced by Dow Chemical Corp., under the trade name SILASTIC . For example, a typical medical-grade silicone (like SILASTIC MDX4-4210 Medical grade elastomer) contains, after curing, cross-linked drmethylsiloxane polymer and silica for reinforcement. Silcones are also reinforced with PET (Dacron) fiber meshes for certain biomedical applications. For implantable medical devices, it is important to realize that the cured polymer contains residual catalysts and silicone cross-linkers, which are necessary for the polymerization. 

Silicone elastomers were first used as the basis for controlled drug delivery systems in 1962, when Folkman and Long discovered that low molecular weight compounds could diffuse, at a controlled rate, through the walls of silicone tubing [18-20]. That observation led to the development of several clinical products for controlled delivery of pharmaceutical agents. Most notably, the Population Council developed tubes of SILASTIC (in this case. 

In early 1960, Swanson ( ) Introduced the use of silicon rubber In this application. A cruciform bar of Silastic provided... 

Silastic J silicone molds were used to prepare tensile microdumbbells. The networks were cured mder N2 according to the schedules in Table II. After test samples were machined, a final postcvire of 10 hrs. at 200°C under vacuum was applied. This postcure was found to give a network with a stable maximum Tg. 

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