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Torsional Relaxation and Volume Response During Physical Aging in Epoxy Glasses Subjected to Large Torsional Deformations

Published online by Cambridge University Press:  16 February 2011

Maria M. Santore  and
Gregory B. McKenna
Maria M. Santore
Affiliation:
Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015
Gregory B. McKenna
Affiliation:
Polymer Division, NIST, Gaithersburg, MD 20899
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Abstract

We present torsional dilatometry experiments to simultaneously measure torque relaxation and volume recovery in an epoxy glass quenched from above its glass transition temperature to below it. Two strain histories are employed: one with strains of equal sizes and a second where small strains follow a large one. The baseline for the thermally induced volume recovery is insensitive to intermittent torsional strains whose magnitude can be well into the non-linear regime. The torque relaxations from equal intermittent mechanical stimuli can be superposed by a time-aging time shift in a way that indicates fast changes cease to occur at ∼104 seconds after the quench, a “mechanical equilibration” time. Stimuli of different sizes can confound superposition via nonlinear effects, but do not affect the ultimate volume recovery of the glass or its mechanical equilibration time. Our results show the signature of rejuvenation; however, this may result from the nonlinear response of the material in a nonisochoric strain history. Our data firmly show that mechanical stimuli do not erase aging or rejuvenate this epoxy.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 215: Symposium R2 – Structure, Relaxation and Physical Aging of Glassy Polymers , 1990 , 81
Copyright
Copyright © Materials Research Society 1991

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