Fourteen numbers of dimetbyldialkoxysilanes were prepared by reacting
dimethylchlorosilane and corresponding alcohols in the liquid phase. P
roperties like density, viscosity, molecular weight, refractive index,
thermal expansion coefficient, oxidation stability, flash point and p
our point were determined by standard methods. Dielectric constant, di
electric loss and breakdown voltage of dimethyldialkoxysilanes are det
ermined and the values are compared against molecular weight, viscosit
y, temperature, pour point along with the values of tetraalkoxysilanes
, polydimethylsiloxanes and coolanols of Monsanto Chemicals in order t
o study their dielectric behaviour. Dipole moment of the samples are o
btained from the plot of molar polarization and reciprocal absolute te
mperature. Dielectric constant of dimethyldialkoxysilanes increases wi
th the increase in molecular size due to increase in polarizability an
d decreases with rise in temperature and frequency due to reduction in
the alignment of the permanent dipoles by the electric field as obser
ved for the polar compounds like polydimethylsiloxanes and coolanols.
The values of dielectric constant of dimethyldialkoxysilanes are highe
r than those of tetraalkoxysilanes and polydimenthylsiloxanes of compa
rable molecular weight due to molecular dissymmetry. Comparable dielec
tric behaviour of dimethyldialkoxysilanes coupled with their better ox
idative and thermal characteristics suggest that these compounds could
be used in some of the power transfer and dielectric coolant applicat
ions in the place of conventional materials for better performance.