METHOD OF DETERMINATION OF DIELECTRIC-RELAXATION CHARACTERISTICS OF PLASTICIZED POLYSTYRENES ON THE BASIS OF CALORIMETRIC GLASS TEMPERATURE

The dielectric loss measurements of different polystyrenes (fractions and blends) with different molecular weights (M(n) 2000-125000 g/mol) were carried out in the frequency range 10(-2)-10(6) Hz and the temper ature range of the glass process (60-degrees-135-degrees-C, depending on the molecular weight). The measurements of the pure fractions showe d that the half-width of the glass relaxation process of the different polystyrenes can be correlated by a straight line, if they are plotte d versus the relaxation frequency maxima of the glass process, regardl ess of the difference in both their molecular weight and glass transit ion temperature. Moreover, the fine structure of the shape. of the gla ss process of polystyrenes with different molecular weights was found to be the same when the glass process appears at the same relaxation f requency range. The addition of oligostyrenes or low molecular < 10% w t additives to the high molecular weight polystyrene did not influence the shape of the glass process. The calorimetric glass transition tem perature of polystyrene was found to be only dependent on the number a verage molecular weight as well as on the number of end groups, but no t on the molecular weight distribution. The obtained experimental resu lts were correlated to develop a method for the estimation of the diel ectric relaxation characteristics (relaxation frequency as well as the shape parameters) of the glass process of plasticized polystyrenes ba sed on the calorimetric glass transition temperature. A method for the analysis of the dielectric relaxation curves of mixtures of label and polymer is suggested.