Silicone Rubber Polydimethylsiloxane

These rubbers are completely synthetic materials with wide applications. They comprise two types, heat-vulcanizing and RTV. Both types have unique properties unobtainable with organic rubbers, particularly where superior endurance and extended life expectancy are required. Silicone elastomers maintain their usefulness from -101 °C to 316 °C. Resistance to oxidation, oils, and chemicals is high 

Solvent-wipe surfaces with acetone, MEK, ethyl, methyl, or isopropyl alcohol, or toluene. 

A simple washing with a mild (Ivory ) soap and 

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Current polymeric entubulization repair methods for peripheral nerve regeneration use various nondegradable and biodegradable materials. The most common nondegradable material investigated has been silicone rubber. Medical grade silicone rubber, polydimethylsiloxane, maintains its shape and can be filled with neurotrophic factors or extracellular... 

Figure 9.3 Weight loss as a function of exposure time with oxygen glow discharge POM polyoxymethylen, PMMA poly(methyl methacrylate), PET poly(ethylene terephthalate), LDPE low density polyethylene, SR silicone rubber (polydimethylsiloxane).

Finger joint replacements are divided into three types (1) hinge, (2) polycentric, and (c) space-fiUer. The most widely used are the space-filler type. These are made of high performance silicone rubber (polydimethylsiloxane) and are stabilized with a passive fixation method. This method depends on the development of a thin, fibrous membrane between implant and bone, which allows pistoning of the prosthesis. This fixation can provide only minimal rigidity of the joint [Swanson, 1973). Implant wear and cold flow associated with erosive cystic changes of adjacent bone have been reported with silicone implants [Carteret al., 1986 MaistrelU, 1994]. 

Another example is that of a mixture which consists of two components which are not miscible with each other over the whole composition range, e.g. trichloroethylene-water. Pervaporadon can be used to remove a small amount of water from trichloroethylene or to remove small amounts of trichloroethylene from water. If silicone rubber (polydimethylsiloxane) is used as a membrane material, good results are obtained if small amounts of trichloroethylene from water should be removed. When the same membrane material is used to remove water from almost pure trichloroethylene, the membrane becomes too highly swollen and the separation and mechanical properties are lost. Thus in order to remove traces of water anotherm eiial has to be chosen, e.g. poly(vinyl alcohol). These extreme examples indicate the influence of composition on the membrane performance. 

In practice, almost all commercial plants use rubbery membranes, predominantly membranes made from silicone rubber (polydimethylsiloxane, PDMS). Rubbery membranes are preferred for several reasons ... 

Recent work has focused on a variety of thermoplastic elastomers and modified thermoplastic polyimides based on the aminopropyl end functionality present in suitably equilibrated polydimethylsiloxanes. Characteristic of these are the urea linked materials described in references 22-25. The chemistry is summarized in Scheme 7. A characteristic stress-strain curve and dynamic mechanical behavior for the urea linked systems in provided in Figures 3 and 4. It was of interest to note that the ultimate properties of the soluble, processible, urea linked copolymers were equivalent to some of the best silica reinforced, chemically crosslinked, silicone rubber... 

Room temperature-vulcanizing (RTV), silicon rubbers make use of the room temperature reaction of certain groups that can be placed on polydimethylsiloxanes, which react with water. When exposed to water, such as that normally present in the atmosphere, cross-links are formed creating an elastomeric product. 

The high mechanical strength of natural and organic rubbers as used in tires is due to the incorporation of pyrogenic carbon blacks as active fillers. Elastomers of a more polar polymer backbone, such as polyacrylates, polyurethanes or polysulphides, require fillers of higher polarity. In particular the performance of polydimethylsiloxane elastomers (silicone rubber) is basically related to the addition of fumed silica. 

Silicone rubbers are formed by an inorganic main chain of oxygen-silicon covalent bonds, with side substituents consisting of methyls, phenyls, vinyls, etc. The most commonly used is polydimethylsiloxane (PDMS) whose structure is given below ... 

In the process of separation of noble gases, silicon rubber membranes [161,162] and high-resistant siloxane rubbers (polyvinyltrimethylsilane—PVTMS and block-copolymer, composed of polyarylate and polydimethylsiloxane of different weigh ratio, the so-called sylar) [163,164] were employed. 

Polysiloxanes are polymeric materials prepared by the condensation of suitably substituted silanes. For the most common form, polydimethylsiloxane (PDMS)—or silicone rubber, the synthesis can be represented formally by the equation. 

The reaction is of practical importance in the vulcanization of silicone rubbers (see Rubber compounding). Linear hydroxy-terminated polydimethylsiloxanes are conveniently cross-linked by reaction with methyldiethoxysilane or triethoxysilane [998-30-1]. Catalysts are amines, carboxylic acid salts of divalent metals such as Zn, Sn, Pb, Fe, Ba, and Ca, and organotin compounds. Hydroxy-terminated polysiloxanes react with Si—H-containing polysiloxanes to... 

Test polymers for visualization studies were polyurethane (Pellethane, 2363-80A, Upjohn), filler-free polydimethylsiloxane (Sil-Med Corporation), two forms of Teflon, sintered (TFE, DuPont) and Fluorofilm (Dilectrix Corporation), and polyurethane-silicone rubber copolymer (AVCOthane 51, AVCO). Samples of 1 cm2 or, for shear studies, 5 X 20 X 0.5-cm sheets, were washed in ionic detergent solution (Alconox) at 60°C for 1 h, rinsed in deionized water, and refluxed in absolute ethanol for 1 h. Materials were dried and stored in a desiccator until use. 

Lipids have proven to be quite active in polymer environments (13-15). Investigations in the 1960 s performed on silicone rubber heart valve poppets (16) demonstrated that polydimethylsiloxanes with low cross-link densities and low silica filler underwent significant lipid uptake in vivo. 

Silicon-based polymers (polyorganosiloxanes, such as polydimethylsiloxane, silicone rubber). 

Single Component System. In a single component system, the drug is encapsulated in its pure form and release rates are essentially zero order (72). Polydimethylsiloxane and polyethylene are the materials most often chosen for encapsulation. Table HI shows some typical release rates reported by Kind, et al. (14), for various steroids through silicone rubber. Clearly, when a solution-diffusion mechanism controls the drug release rate, drug permeabilities can be expected to vary widely. 

Synonyms Polydimethylsiloxane elastomer Polydimethylsiloxane rubber Polysilicone Silicone rubber... 

Silicone Release Agent 5038. See Dimethicone Silicone Resin Emulsion BS 43A. See Polydimethylsiloxane Silicone rubber. See Silicone elastomer Silicone Systems 820, Silicone Systems 872, Silicone Systems 873, Silicone Systems 876 Silicone Systems 878, Silicone Systems 882 Silicone Systems 883, Silicone Systems 886] Silicone Systems 889] Silicone Systems 921] Silicone Systems 922] Silicone Systems 923] Silicone Systems 924] Silicone Systems 925] Silicone Systems 972] Silicone Systems 972P, Silicone Systems 976 Silicone Systems 982] Silicone Systems 982P] Silicone Systems 983] Silicone Systems 984] isilicone Systems 986. See Silicone... 

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