Effect of cyclic straining with various rates on stress softening/hysteresis and structural evolution of filled rubber: A time-resolved SANS study

Abstract

The effect of cyclic straining on stress softening/hysteresis and structural evolution silica filled deuterated silicone rubber (SFdSR) during cyclic deformation has been investigated. In situ rheo-small-angle neutron scattering (Rheo-SANS) measurements were conducted with engineering strain rates (έ) spanning from 0.001 to 0.1 s−1. Moreover, superimposed time-resolved SANS technique is utilized. The non-linear behaviors all exhibit strong έ and cycle-number (No.C) dependency. Rheo-SANS suggests that the orientation of bound rubber responses sensitively to the strain, έ, and No.C, which presents an accumulative characteristic, associated with cyclic stress relaxation of the engineering stress-nominal strain curves. All the results consistently suggest that some substantial permanent changes occur within bound rubber, filler network, and rubber matrix after deforming the samples of virgin state. Evolutions would drastically develop during the initial couple of cycles, then accumulate and reach to a newly established equilibrium under constant έ, as long as the maximum strain is not exceeded.