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

Supercritical CO 2 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 scCO 2 foaming behavior and corresponding properties. Therefore, a strategy was proposed to take fluorescence’s advantage of real-time and field visualization in scCO 2 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 scCO 2 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.