Dynamic Response and Damping Behavior of Heterogeneous Polymers. Part 2.
Abstract
The mechanical properties of a polystyrene - polybutadiene - polystyrene block copolymer of molecular weight 9500/37500/9500 were determined at temperatures between -60 and 130 C in sinusoidal shear over a frequency range from 25 to 1250 Hz, in tensile stress relaxation from -70 to 70 C over a time scale ranging from 1 to 1000 sec. and in tensile creep from -40 to 75 C over a time scale from 10 to 10,000 sec. The dynamic mechanical properties of a l,2-polybutadiene - polystyrene block copolymer of molecular weight 160,000/40,000 were measured at ten temperatures, between -10 and 80 C over a frequency range from 250 to 2500 Hz. The dynamic measurements were made on compression molded specimens. The relaxation and creep data were obtained from solution cast samples. These materials are not thermorheologically simple because the polystyrene - polybutadiene moieties of the molecules form separate microdomains, similar to, but smaller than the domains in polyblends. Empirically, the response curves obtained at different temperatures could be shifted into superposition and plots of the logarithmic shift factors against temperature showed qualitatively similar curves for each mode of measurement. In the triblock copolymer the temperature dependence is dominated at low temperatures by the l,4-polybutadiene moiety and at high temperatures by the polystyrene moiety. Because of the rather large difference in the respective glass transition temperatures (about 200 C) the two regions Df dominance were quite well separated. At the lower temperatures, where the polystyrene domains essentially act as inert filler only, the temperature dependence could be well described by equations of the WLF form which were, however, different for the data derived from the dynamic and from the step function .
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1969
- Accession Number
- ADA307846
Entities
People
- D. Froelich
- Maurice Morton
- N. W. Tschoegl
Organizations
- University of Akron