THERMODYNAMIC CHARACTERIZATION OF CARBON BLACK-FILLED RUBBERS

Unfilled and carbon black-filled samples of synthetic isoprene- and bu tadiene-methylstyrene based rubbers were characterized by precise heat capacity measurements in the temperature interval 4.2-300 K. Both unf illed samples proved to behave in an essentially fracton-like way in t he temperature interval 6-30 K. The excess thermodynamic quantities de rived from the smoothed data suggested that the thermodynamic state of the elastomeric phase in the filled rubbers was intrinsically unstabl e.