Polydimethylsiloxane products

Polydimethylsiloxane [9016-00-6] [63148-62-9], or sikeone, is used at a level of approximately 10 parts per million to control foam in food products. The sikeone disperses itself throughout the kquid film that makes up the foam and causes it to coUapse (15). 

Dimethicone is another name for polydimethylsiloxane and is used to impart a soft velvety feel to hair or skin products. It is also used as an emulsifier for water-in-oil emulsions. 

Dense membranes are a special type of polymeric membranes. Jacobs et al. published on the use of polydimethylsiloxane (PDMS) dense membranes in the hydrogenation of dimethylitaconate and acetophenone using standard homogeneous catalysts (see Section 4.6.1)[48]. The membranes were homemade from a PDMS solution in hexane, which was cross-linked in a vacuum oven at 100°C. The membranes were able almost completely to retain unmodified Ru-BINAP dissolved in isopropanol. However, as mentioned earlier, these applications will strongly depend on the size, i.e. molecular weight, of the substrate to be converted in order to guarantee a sufficient difference in size of the product and the catalyst to be retained. 

Miscellaneous compounds. Other materials used include FC-171, fluorocarbon surfactant, 3M Industrial Chemical Products Division, St. Paul MN 55144-1000 Byk 306, Bykchemie USA, Wallingford, CT 06492 Polyol (poly-caprolactonetriol a polyester polyol), and Silwet L-7602 (polyalkylene oxide modified polydimethylsiloxane), both from Union Carbide Chemicals and Plastics Co., Inc., Danbury, CT 06817-0001. 

Inhibition of polydimethylsiloxane hydrolysis on soils [52,60] and clays [25] by high moisture levels has been described, which is in general attributed to their low water solubility. This is not expected to be applicable to the more soluble surfactant analogues, however, which show increased water solubility with degradation [10,12,15], and which are used at concentrations much lower than are required for the formation of hydrophobic degradation products. 

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. 

Figure 12 shows an optional step at the end of the process in which the silica is chemically reacted with a silicone oil, typically polydimethylsiloxane, to render the product hydrophobic. Other aftertreatments are also commonly employed, such as wax coatings that enhance the performance of precipitated silicas used as flatting agents in paints (78). 

Copolymers. Copolymers from mixtures of different bisphenols or from mixtures of dichlorosulfone and dichlorobenzophenone have been reported in the patent literature. Bifunctional hydroxyl-terminated polyethersulfone oligomers are prepared readily by the polyetherification reaction simply by providing a suitable excess of the bisphenol. Block copolymers are obtained by reaction of the oligomers with other polymers having end groups capable of reacting with the phenol. Multiblock copolymers of BPA-polysulfone with polysiloxane have been made in this way by reaction with dimethyl amino-terminated polydimethylsiloxane the products are effective impact modifiers for the polyethersulfone (79). Block copolymers with nylon-6 are obtained when chlorine-terminated oligomers, which are prepared by polyetherification with excess dihalosulfone, are used as initiators for polymerization of caprolactam (80). 

The mechanism of this depolymerization is unlikely to be biological but rather is thought to involve catalysis by clay minerals within the soil. At high water levels, access of the hydrophobic polydimethylsiloxane to the active sites on the clay may be limited, thus slowing the depolymerization. The dimethylsilanediol (10) is the major product species... 

After exposure the cell was vented through 10 ml of hexane. Following depressurization the cell was rinsed several times with the same 10 ml solution. A GC analysis (HP 5890A gas chromatograph with a 25m polydimethylsiloxane capillary column, FID detector) of the hexane extract solution revealed the product isomer distribution. 

Three classes of PSAs used most widely in transdermal systems are polyisobutylene (PIB), polyacrylate, and polydimethylsiloxane (silicone). More recently, hydrophilic adhesive compositions, hydrogels composed of high-molecular-weight polyvinylpyrrolidon (PVP) and oligometric polyethylene oxide (PEO), have been shown to be compatible with a broad range of drugs and are used in several commercial products.60... 

Silanols are stronger acids than their hydrocarbon homologues. Condensation reactions are governed by the polarity of the Si O and -OH bonds. The most widely used product is polydimethylsiloxane, PDMS, R1 = R2 = -CH3. The formation of cyclic oligomers always competes with that of linear chains. 

In this article, we report on the fabrication and performance of microreactors constructed of silicon and polydimethylsiloxane (PDMS). The resulting structures contain immobilized enzymes for converting biochemical substrates to useful products or for breaking down organics into waste streams. 

A FePc complex encaged in the zeolite Y supercages, in its turn, can be wrapped in a polydimethylsiloxane membrane, thus acting not only as a mechanistic but also as a formal mimic of Cytochrome P450 often found in cell membranes.[57] Such membranes, contacted on one side with substrate and on the other side with oxidant, catalyse oxygenation reactions in a membrane reactor in the absence of any solvent, the majority of the product amount being recovered from the more polar phase. 

The production of polydimethylsiloxane elastomer comprises three main stages the hydrolytic condensation of dimethyldichlorosilane the depolymerisation of the products of hydrolytic condensation the polymerisaton of dimethylcyclosiloxanes. 

The production of polydimethylsiloxane elastomer relies heavily on the purity of the parent dimethyldichlorosilane, since impurities of other monomers noticeably impair the properties of the elastomer and rubbers based on it. Methyltrichlorosilane has the strongest negative effect when dimethyldichlorosilane with impurities of this monomer is subjected to hydrolytic condensation, linear oligodimethylsiloxane develops branched me-... 

Our industiy manufactures dimethyldichlorosilane of 99.98% purity and 54.85-55% chlorine content. This dimethyldichlorosilane can be used as raw stock in the production of polydimethylsiloxane elastomer without any additional rectification. 

Dimethyldichlorosilane used in the production of polydimethylsiloxane elastomer should meet the following technical requirements ... 

The product of depolymerisation is a mixture of cyclic dimethylsilox-anes with tetramer (mostly [(CH3)2SiO]4 (the boiling point is 175 °C) with an impurity of trimer [(CH3)2SiO]3 (the boiling point is 134 °C) and pen-tamer [(CH3)2SiO]5 (the boiling point is 210 °C). It is used as raw stock in the production of polydimethylsiloxane elastomers SKT, SKTV, SKTN, etc. 

When SKTN elastomers are produced, dimethylcyclosiloxanes are polymerised with 2 N potassium hydroxide solution (0.005% of the amount of the polymerised substance) the molecular weight of the polymer is regulated by water supply (diluting the alkali). The raw stock for polymerisation can be the depolymerisate obtained at the depolymerisation stage of the product of hydrolytic condensation of dimethyldichlorosilane in the production of polydimethylsiloxane elastomer SKT. 

A dried 500-ml round bottom flask was charged with bis(a, -hydroxybutyl polydimethylsiloxane) (Mj, 1624daltons 0.0185 mol) and fumaryl chloride (0.0418 mol) and then heated to 60° C for 2 hours and concentrated. The residue was treated with 3 mg of water and 30 ml of THF and refluxed until no IR evidence of acid chloride absorption was present. The mixture was next concentrated, the residue dissolved in 200 ml diethyl ether, extracted three times with 50 ml, dried with MgS04, re-concentrated, and the product was isolated. 

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