ISSN:
1436-2449
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract We have performed mechanical and dielectric dynamic measurements above the glass-transition temperature range of two glassy-polymers: Poly(Hydroxyether of Bisphenol-A) and Poly(Carbonate of Bisphenol-A). From these measurements the temperature dependence of mechanical and dielectric mean relaxation times has been calculated. Results obtained have been compared with the viscosity temperature behaviour of the same polymers, which has been reported elsewhere. Both, relaxation times and viscosity temperature behaviour can well be described by Doolittle functional forms, exp{1/[αf(T-To)]}, with the same values of To but different values of the apparent free-volume expansion coefficient, αf. This difference in the experimental behaviour has been addresed in the framework of the free-volume model ideas. In this context, the different values of αf obtained from viscosity and relaxation times temperature behaviour can be understood assuming different values of critical volume controlling the molecular motions associated to viscosity and relaxation processes. Similar conclusions have also been obtained by means of a fine revision of the viscosity and relaxation times data of another two glassy-polymers: Poly(Arylate) and Poly(Sulfone of Bisphenol-A), reported previously.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00255820
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