Nanocavitation in polymer composites by SAXS/SANS
Upon deformation of nanocomposites consisting of chemically or physically connected network, entropy of the system changes which leads to short- and long-range restoring forces. Any heterogeneity (imperfection) in the matrix leads to localized large viscoelastic deformations and consequently a heterogeneous stress distribution. The localized high level of stress could initiate molecular damage through irreversible breakage of polymer chains, which follows by cavitation and a macroscopic crack propagation in the material. Our aim here is to provide a molecular level understanding of cavity formation upon loading and unloading in cross-linked rubbers by using in-situ SAXS.
There have been several publications on applying the technique to investigate the effect of different parameters on nanocavitations in the bulk and around the crack tip, such as the effect of filler type (carbon black and silica) and concentration, silanization of silica, maximum load and cyclic loading. However, there are still many interesting questions to be answered in this area, such as, what is the influence of phase morphology in polymer blends on cavity formation and how filler dispersion in such systems affects the damage mechanisms? In this proposal, we are aiming to study the effect of polymer blend phase morphology on cavity formation in the bulk and around the crack tip by varying type of polymers in a blend, blend ratio, curing time and curing temperature. The effect of filler micro-dispersion on molecular damage mechanisms will be studied by varying filler type (carbon black and silica) and polymer-filler coupling agent (grafting).