  In this work, we investigate signatures of physical aging in an aqueous
dispersion of Carbopol that shows yield stress and weak enhancement in elastic
modulus as a function of time. We observe that the creep curves, as well as
strain recovery, show a significant dependence on waiting time elapsed since
shear melting. The corrected strain, which is the strain in excess of the
recovered strain, has been observed to show time waiting time superposition in
the effective time domain, wherein time is normalized by time-dependent
relaxation time that shows a power-law dependence. The corresponding power law
exponent, which is close to unity in a limit of small stresses, decreases with
stress and tends to zero as stress approaches the yield stress. For a range of
stresses, the material shows time stress superposition suggesting the shape of
the evolving relaxation time spectrum to be independent of the time as well as
the stress. This work, therefore, suggests the presence of physical aging in an
aqueous dispersion of Carbopol even though the elastic modulus shows only a
weak enhancement. We also discuss Andrade type of creep behavior in aqueous
Carbopol dispersion.

Soft Condensed Matter