Polymethylphenylsiloxane

Silicones. Polydimethylsiloxanes, polydiphenylsiloxanes, and polymethylphenylsiloxanes are generally called silicones (see Silicon COMPOUNDS, silicones). With a repeating unit of alternating silicon—oxygen, the siloxane chemical backbone structure, silicone possesses excellent thermal stability and... 

Methyl(phenylaminomethyl)diethoxysilane is used as a modifying agent for some polymethylphenylsiloxane varnishes and polyolefines, as well as to obtain binding agents for fiberglass plastics. 

Preparation of polymethylphenylsiloxanes, polydimethylphenylsiloxanes and varnishes based on them... 

Structure II polymers are relatively elastic when polymethylphenylsiloxanes are obtained by the hydrolytic cocondensation only of trifunctional monomers (e.g., methyl- and phenyltrichlorosilanes), there are polymers with low elasticity. Polydimethyl- and polymethylphenylsiloxanes can be modified with organic polymers (polyester, epoxy) or silicone substances, e.g. methyl(phenylaminomethyl)diethoxysilane. The modification of polydimethyl- and polymethylphenylsiloxanes improves some properties of these polymers and varnishes based on them in particular, it considerably increases adhesion and mechanical durability of varnish films. 

The production of polydimethyl- and polymethylphenylsiloxanes and varnishes based on them comprises two main stages hydrolytic cocondensation solvent distillation and filtering of varnish. 

At present polydimethylphenylsiloxane and polymethylphenylsiloxane varnishes are produced both by the periodic and by the continuous technique. 

The semicontinuous and continuous technique for the production of polydimethylphenylsiloxane and polymethylphenylsiloxane varnishes have no such drawbacks. 

Polydimethylphenylsiloxane and polymethylphenylsiloxane varnishes, which are in ever greater demand, are also produced by the continuous technique (Fig. 71). 

From container 9 the flushed hydrolysate is sent to partially distil the solvent into tank 77 to produce modified polymethylphenylsiloxane varnishes, it is first mixed with polyester or epoxy polymer in apparatus 7 0, and then sent into the tank. From the tank, the hydrolysate is sent to condensation into three-sectioned apparatus 12. In the first section the solvent is additionally distilled and the product of the hydrolytic cocondensation is partially condensed in the second section it is further condensed at 125-... 

Polydimethylphenylsiloxane and polymethylphenylsiloxane varnishes are transparent liquids with colour ranging from light yellow to light brown. They can be dissolved in toluene, benzene, xylene and other nonpolar organic solvents but are not soluble in water and alcohols. 

Polydimethylphenylsiloxane and polymethylphenylsiloxane varnishes are widely used in the electrotechnical industry. Some of them (e.g. varnishes based on methyl- and phenyltrichlorosilanes) can be used in certain conditions as binding agents for pressure materials however, these varnishes enter the nonmeltable and nonsoluble state only after prolonged heating and are impractical for the production of plastic laminates. 

The most important properties of some insulating polydimethylphenylsiloxane and polymethylphenylsiloxane varnishes are given in Table 26. 

Preparation of polymethylphenylsiloxanes with active hydrogen atoms and vinyl groups at the silicon atom... 

Polymethylphenylsiloxanes with active hydrogen atoms and vinyl groups at the silicon atom are industrially manufactured without solvents and are of great practical interest, since they do not release volatile substances when processed into goods. The process occurs in the presence of a catalyst (H2PtCl6 or dimethylformamide) according to the mechanism of hydride attachment. 

That is why articles made from these polymethylphenylsiloxanes do not shrink. 

The preparation of polymethylphenylsiloxanes with active hydrogen atoms and vinyl groups at the silicon atom (Fig, 73) begins with the preparation of the reactive mixtures in enameled mixer 8 with an agitator and a water vapour jacket. Different polymers require different organochlorosilanes in different mole ratios. 

Figure 16. Dielectric loss curves of polymethylphenylsiloxane (PMPS) measured at a constant temperature (T — 273 K) and different pressures. The data have been shifted to superimpose onto the data for P — 42.4 MPa.

The most-used silicone lubricants in the fibre finishing applications are polydimethylsiloxane, polymethylphenylsiloxane, oleophilic silicone/organic copolymer (Fig. 5.7a), and poly(glycol silicone copolymer) (Fig. 5.7b). The analysis of silicones can be conducted by FTIR. A strong and often broad absorption in the 1000-1100 cm region can be attributed to the Si-O vibration. A peak at 1100 cm shows the Si-O-Si vibration. A sharp peak at 1260 cm" indicates the Si-( II. stretching absorption.- ... 

Methylchlorosilane mixtures have also been separated397 on a column consisting of Rysorb impregnated with a polymethylphenylsiloxane oil. 

Eight components of polymethylphenylsiloxanes were identified430 by the use of columns of Aerosilogel A-380 or Silochrom C-80 supporting 3,3 -oxydipropionitrile and detected by ultraviolet spectroscopy. 

Figure 17-3. Structure and viscosity of silicones. 1 Polydimethyl-siloxane. 2 Polyoctylmethylsiloxane. 3, 3 Polymethylphenylsiloxane. From data by Jakobsen, Sanborn and Winer [8].

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