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Physical aging time scales and rates for poly(vinyl acetate) stimulated mechanically in the T g ‐region
Author(s) -
Delin M.,
Rychwalski R. W.,
Kubát J.,
Klason C.,
Hutchinson J. M.
Publication year - 1996
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10697
Subject(s) - materials science , dynamic mechanical analysis , composite material , glass transition , vinyl acetate , accelerated aging , polymer , copolymer
The physical aging behavior of poly(vinyl acetate), PVAc, in the T g ‐region has been investigated using dynamic mechanical analysis (DMA). Tests in shear and flexure modes were performed for samples quenched from a stabilization temperature of 40°C to aging temperatures 35.0°C and 32.5°C (down‐jumps), and from equilibrium at a stabilization temperature of 32.5°C to aging temperature 36.2°C (up‐jump). Volume recovery was investigated for the same thermal histories using mercury‐in‐glass dilatometry. The time scales for the evolution of the storage and loss moduli during physical aging have been compared with the volumetric time scales. Aging rates, µ, have been calculated in the frequency and time domains. The evolution of dynamic mechanical properties during aging is found to be different from the volumetric behavior. In the case of the temperature down‐jump, the evolution of the volume ceases earlier than that for the storage and loss moduli. In the up‐jump experiment, the opposite is found. Aging rates for the storage and loss moduli are analyzed. A suggestion is offered that the evolution of dynamic mechanical properties during physical aging is retarded by the cyclic mechanical stimulus, and that this effect (rejuvenation) is more noticeable the higher is the damping; consequently rejuvenation in the T g ‐region can be caused by small strains in dynamic mechanical analysis.