Dimethyl silicone polymer

SE-30, OV-1, and OV-101 are dimethyl silicone polymers which may be regarded as equivalent as... 

MEMBRANE SEPARATIONS TECHNOLOGY Table A1.6 Gas Selectivity for Dimethyl Silicone Polymer ... 

Dimethyl silicone polymers are, because of their relatively low polarities, relatively compatible with hydrocarbons and easily swollen by fuels. Substitution for the methyl functionality by polar cyanoethyl and trifiuoropropyl groups imparts significant polarity to these elastomers and makes them resistant to swelling by nonpolar substances these specialized polymers can be compounded into very useful adhesives and sealants for applications requiring fuel resistance. 

Method 2. Reequilibration of Cyclic Dimethylsiloxanes Recent evidence supports the presence of macrocyclic poly(dimethylsilox-anes) in dimethyl silicone polymers (22,23,31). In what is really a ring-opening followed by a ring-forming polymerization, octamethylcyclotetrasiloxane was heated with traces of potassium hydroxide with or without a diluent and chain-stopped with trimethylchlorosilane/pyridine. 

Syltheiin 800 (Dow Corning Coiporation). A silicone polymer (Dimethyl Polysiloxane) recommended temperature range —40°C to 400°C similar to Syltherm XLT, more appropriate for somewhat higher temperatures flash point is I60°C,... 

Cu and Ag on Si(lll) surfaces. In the last example, we come back to surfaces. It is well known (44-46) that Cu catalyzes the formation of dimethyl-dichlorosilane from methylchloride and solid silicon, which is a crucial technological step in the synthesis of silicone polymers. Even today, the details of the catalytic mechanism are unclear. Cu appears to have unique properties for example, the congener Ag shows no catalytic activity. Thus, the investigation of the differences between Cu and Ag on Si surfaces can help in understanding the catalytic process. Furthermore, the bonding of noble metal atoms to Si surfaces is of great importance in the physics and chemistry of electronic devices. 

Dimethyl Silicone Elastomers They are having linear polymers of very high Molecular weight within the range of 30,000-7,00,000. In order to prepare these polymers, dimethyl dichlorosilane is made to dissolve in ether and the solution is then mixed with excess of water. 

Thus, to make a trimethyl end-capped silicone polymer with a total DP of x + y + 2, one would start with 1 mol of MM (hexamethyldisiloxane), x mol of D (dimethyl) units, perhaps in the form of octamethylcyclotetrasiloxane and ymol of D (tetramethylcyclotetrasiloxane... 

Another relatively nonpolar liquid, but one with a very high temperature limit, is a carborane silicone polymer called Dexsil, first synthesized by Olin Chemical in 1964 and now manufactured by Analabs and by a company bearing the Dexsil name. Its structure is shown in Figure 8.16. Three polymers are available that differ in the substitution on the methyl silicone backbone in a way similar to the silicones discussed above Dexsil 300 is dimethyl silicone, as shown in the figure Dexsil 400 is the methyl-phenyl analog and Dexsil 410 is the methyl-cyanopropyl analog. The temperature range over which they can be used is approximately 50 to 400°C. 

H9. Hunter, M. J., E. L. Warrick, J. F. Hyde, and C.C. Currie Organo-silicon polymers II. The open chain dimethyl oxanes with trimethyl-siloxy end groups. J. Am. Chem. Soc. 68, 2284—22 (1946). 

Both Neish and Speakman Nature, 1945, 156, 176) and Wolsey and Alexander (Brit. Pat. 594901, 1947), showed that wool could be made unshrinkable by depositing upon it a silicon polymer. Alexander (J.S.D.C., 1950, 66, 349) considers that this is the only example of true masking of the scales with no spot welding involved. The process is described in detail by Alexander, Carter, and Earland J.S.D.C., 1949, 65, 107). The wool was treated with a substance of the general formula R.R. SiCl in an organic solvent such as carbon tetrachloride. The experiments were carried out with dimethyl silicon dichloride. The goods were immersed in the solution, hydroextracted, and then soaked in water at room temperature and dried, when the silicon compound was deposited on the surface of the fibres as an insoluble polymer. 

Silicone Rubbers. As pointed out earlier, the silicone rubbers are formed by reaction of a peroxide with a dimethyl silicone fluid. In practice, the fluid, peroxide, and appropriate inorganic iillers (titanium diojdde, ranc oxide, iron oxide, silica, etc.) are milled together. Molding at about 150 C develops the rubbery product. By alteration of the polymer and by appropriate selection of kind and amount of filler, rubbers of different types may be prepared. 

Figure 9-33. Selectivity of different polymer membranes to He-N2 separation as a function of nitrogen permeability (n, incm /(cm x atm x s)) (1) polyvinylidenechloride (2,4)polyethylene terephthalafe (3) polyvinylfluoride (5) polyvinylchloride (6) polyamide (7) plasfified polyvinylidene chloride (8) cellulose nitrate (9) polypropylene (lO)fluoroplast (26) (ll)co-polymer of isoprene (74%) and acryl-nitryl (26%) (12, 18, 20) different co-polymers of butadiene and acryl-rritryl (13) polyacrylate (14) polycarbonate (15) polyisobutylene (16) bulyl latex (17) co-polymer of vinyl chloride and vinyl acetate (19, 37) butyl acetate of cellulose (21) polyethylene vinyl acetate (22) polybutadiene (23) special polymer SKI-3 (24) natural latex (25) nitryl silicon latex (26) dimethyl silicon latex (27) special polymer SKS-30 (28) special polymer SKMS-50 (29) special polymer SKMS-30 (30, 34, 35) high-density, medium-densily, and low-density polyethylene (31) polyethylene with 5% soot (32) co-polymer of ethylene (90%) and propylene (10%) (33) co-polymer of ethylene (96.5%) and vinyl acetate (3.5%) (36) triacetate of cellulose (38) acetate cellulose (39) polystyrene.

The polymer has a waxy texture and is insoluble in a wide range of organic solvents. It does, however, form gel-like materials with solvents such as tetrahydrofuran, dioxane and chloroform. Not surprisingly in view of this, a mixture of a small amount of it and a large amount of a 1000 cs dimethyl-silicone oil forms a stiff, stable grease. When purified the polymer is a very pale blue. 

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