MOLECULAR-TRANSPORT CHARACTERISTICS OF SANTOPRENE THERMOPLASTIC RUBBER IN THE PRESENCE OF ALIPHATIC ALKANES OVER THE TEMPERATURE INTERVAL OF 25-DEGREES-C TO 70-DEGREES-C

Solvent transport into Santoprene thermoplastic rubber samples exposed to n-alkanes (C-5 to C-16), 2,2,4-trimethylpentane, cyclohexane and 1,2,3,4-tetrahydronaphthalene in the temperature interval 25-70 degrees C has been studied, For all liquids, equilibrium penetrant uptake and degree of penetrant overshoot have been influenced by factors such as penetrant size, shape, polymer morphology and temperature. Sorption-desorption-resorption-redesorption experiments have been performed for some typical solvents at 25 degrees C to determine the true sorption equilibrium and transport parameters. The values of the polymer-solvent interaction parameters have been used to calculate the molar mass between crosslinks of the network polymer. Kinetic rate constants and the activation parameters for the process of diffusion, permeation and sorption:desorption have been calculated. The transport coefficients and the activation parameters showed a dependence on the size of the penetrant molecules. The transport phenomenon was found to follow the Fickian-type mechanism.