ISSN:
1435-1536
Keywords:
Splitting region
;
physical aging
;
glass transition
;
shear modulus
;
poly(ethyl methacrylate)
;
poly(n-propyl methacrylate)
;
poly(n-butyl methacrylate)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract A systematic study of the dynamic shear modulusG *=G′+G″ in three poly(alkyl methacrylates) (PEMA, PnPMA, PnBMA) at frequencies between 0.001 and 500 rad/s is presented. As the αβ splitting frequencies ωs are low, aging effects can be observed in the splitting region. There is a systematic shift of the splitting frequency ωs to lower values with increasing length of the alkyl side group. In PnBMA a separate shear α appearance is observed about two frequency decades below the local mode β. This is discussed in terms of the concept of minimal cooperativity. Aging effects are: Shift of the maximum loss frequency ωα to lower values, peak sharpening of the α relaxation, and intensity changes of α and β. These effects are discussed in terms of the sequential aging concept. Aging leads to a pronounced bending of the α traces upwards from the equilibrium line in the Arrhenius diagram. These non-equilibrium phenomena are promoted by the small slope mα=d(log ωα)/dT of the α trace in the splitting region.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00654174
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