Viscoelastic behaviour of polysiloxane - Based compositions over a wide frequency and temperature range

Dynamic, torsion mechanical studies of two polysiloxane based compositions, Polastosil ABM45 and R-P, in wide frequency (0.2 - 100 Hz) and temperature (-140 - 0 degrees C) ranges and for linear range of strain amplitude (gamma = 0.2 %) are presented. The observed G'-minima, near -90 degrees C, magnitudes of which are a decreasing function of frequency proved to be the manifestation of some reversible kinetic transition to a more ordered, crystalline structure.The enthalpy of activation for that transition was estimated to be of the order of 19 kJ/mole. On the basis of DSC measurements the average number of links between polymer chains formed during the crystalization was found to be within the range of 120 - 600, depending on the preliminary cooling rate.