Ultrasonic Absorption and Dielectric Loss in Heterophase Block Copolymers.
CALIFORNIA UNIV BERKELEY DEPT OF CHEMICAL ENGINEERING
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A styrene-butadiene-styrene block copolymer SBS and a plasticized SBS were studied as a function of temperature by an ultrasonic wave propa-gation technique at 9 MHz. Two absorption maxima were found for each of these polymers, one being attributable to the primary glass transition of the polybutadiene blocks and the other to that of the polystyrene blocks. The SBS was cast from two different solvents, benzene and methyl ethyl ketone-tetrahydrofuran. Parallel dielectric loss measure-ments were also made of the SBS in the frequency range of 50 Hz to l0 to the 5th Hz. The dielectric data and the ultrasonic data can be correlated by an Arrhenius-type equation. The polystyrene loss peak in the ultra-sonic data were found to be much weaker than the polystyrene loss peak. However, these two peaks were of comparable magnitude in dielectric data. Ultrasonic data were also compared with low frequency dynamic mechanical data 11 Hz and stress relaxation data through the use of simple time temperature superposition principle. Author, modified-PL