Fluorescence assisted visualization and destruction of particles embedded thin cell walls in polymeric foams via supercritical foaming

Supercritical CO2 foaming is widely used to prepare microcellular foams and particles are frequently added to regulate cellular structure. Nevertheless, microcellular foams present a complicated structure (three-dimension cells and two-dimension cell walls embedded with particles), which is a huge challenge to enlighten scCO2 foaming behavior and corresponding properties. Therefore, a strategy was proposed to take fluorescence’s advantage of real-time and field visualization in scCO2 foaming: (1) cell wall rupture process was studied via in-situ visualization; (2) dual fluorescence design was used to construct particle dispersive state in a cell; (3) polystyrene particles were chemical fluorescence modified to resist strong extraction of scCO2 fluid. This work reveals that effect of particles on bubble nucleation is two folds: interface promoted bubble nucleation, but elastic strain energy inhibited bubble nucleation. By in-situ visualization, irregular particle dominates in initiating cracks in cell walls due to the much larger stress concentration compared with spherical particles.