Siloxane, dimethyl methylphenyl

Silicone PSAs are blends or reaction products of the combination of a poly-organosiloxane, such as poly(dimethyl siloxane) or its copolymers with diphenyl-siloxane or methylphenyl siloxane, with a polysiloxane resin, which is largely inorganic. Pendant vinyl groups may also be incorporated into silicone PSAs,... 

Poly(dimethyl/methylphenyl siloxane)s and poly(dimethyl/diphenyl siloxane)s have been prepared with a range of phenyl contents and their thermal degradations studied. The products of degradation are shown to be benzene and a complex mixture of cyclic oligomers, the latter being analysed by GLC, mass spectrometry, and n.m.r. spectrometry. The mechanism of degradation is discussed in relation to the degradation reactions previously described for (PDMS) and poly(methylphenyl siloxane)s. A study of soluble and insoluble heat stability additives for (PDMS) has been reported and a mechanism of stabilization proposed. ... 

The NMR data presented above reveal a dynamic heterogeneity of filled PDMS in the frequency range from about 10 kHz to 100 MHz. To determine whether the heterogeneity remains at lower fi equencies, dynamic mechanical measurements are performed. The results for cured, unfilled silicon rubber are compared with those for filled samples containing different fraction of hydrophilic Aerosil (380 m g ). For a more straightforward analysis of the mechanical experiments, a random poly(dimethyl/methyl-phenyl) siloxane copolymer containing approximately 90 mol% dimethyl- and 10 mol% methylphenyl-siloxane units has been used for sample preparation. This copolymer is fully amorphous over the whole temperature range. The results of torsion experiments at a frequency of 1.6 Hz are shown as a function of temperature in Fig. 7. 

A random siloxane copolymer containing 90 mol% dimethyl-, 10 mol% methylphenyl-, and 0.3 mol% methylvinyl-chain units is used for the sample preparation. The copolymer is filled with hydrophilic Aerosil (300 m g ) (A300) and hydrophobic Aerosil (60 m g ) (AM60). The weight ratio filler/elastomer is 30 100. 

Retention data have been listed for374 44 alkyl-chloro and chlorophenylsilanes, 34 linear and branched dimethyl and methyl-vinylsiloxanes, 14 cyclic dimethyl and meth-ylvinylsiloxanes and 6 linear methylphenyl- and ethoxyvinyl-siloxanes. 

Wurst and Chur cek have listed retention data for 44 alkyl-chloro and chlorophenylsilanes, 34 linear and branched dimethyl and methyl-vinylsiloxanes, 14 cyclic dimethyl and methylvinylsiloxanes and 6 linear methylphenyl and ethoxyvinyl-siloxanes. They propose a modification of the retention index which is calculated from the retention times of the organosilicon compounds and the retention times of the most closely related dimethylsiloxanes. Furthermore,they claim to validity the new retention index by analysis of mixtures of low molecular weight organosilicon compounds. 

Figure 19 Normalized photoemission currents from silicone oils. AK — poly-dimethyl-silox-ane AS, AP poly-methylphenyl-siloxane. (Redrawn from the data of Koizumi, H., Lacmann, K., and Schmidt, W.R, /. Phys, D AppL Phys, 25, 857,1992.)...

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