Signatures of Overaging in an Aqueous Dispersion of Carbopol

Abstract

In this work, we study the effect of the deformation field on the physical aging behavior of an aqueous Carbopol dispersion. It is composed of soft swollen particles of gel that get deformed and acquire a polygonal shape, with flat interfaces rendering the dispersion a soft solid-like consistency as filled volume fraction approaches unity. It has been proposed that owing to release of stored elastic energy in the deformed particles, Carbopol dispersion undergoes microstructural evolution that is reminiscent of physical aging in soft glassy materials. We observe that application of moderate magnitude of oscillatory strain to Carbopol dispersion slows down its relaxation dynamics, thereby showing characteristics of overaging. On the other hand, the sufficiently high magnitude of strain makes the relaxation dynamics faster, causing rejuvenation. We also solve the soft glassy rheology model, which, when subjected to the same flow field, corroborates with experimental observations on the Carbopol dispersion. This behavior, therefore, suggests that in a system of jammed soft particles of Carbopol, the particles occupying shallow energy wells upon application of moderate strain field adjust themselves in such a manner that they predominantly occupy the deeper energy wells leading to observe the overaging dynamics.

Effect of thermal and mechanical rejuvenation on the rheological behavior of chocolate

“…However, for polymeric glasses, it has been observed that mechanical rejuvenation may not have the same effect as thermal rejuvenation as both take the system to different sections of the energy landscape 47,49 . The actual effect of mechanical rejuvenation could be so complex that for intermediate strengths of the deformation field, it could increase the relaxation time than decrease 50,51 .…”