Understanding bubble nucleation is as necessary to polymer foaming as it is complex. So much is still to be determined that the problem seems daunting at times. However, by combining quality experimental results with incisive theoretical approaches, a greater understanding may be on the horizon. The problem is twofold: experimental nucleation rate data is limited and approximations must be made to classical nucleation theory due to the experimental inaccessibility of parameters. As such, the theory differs from experimental values by multiple orders of magnitude and predictions vary greatly based on approximations, making comparisons difficult. We use a scaling approach to help bridge the gap. Using an optical viewing cell and high-speed camera, we have been able to determine nucleation rate data for a polystyrene/CO_2 system. The work to form a critical nucleus can then be extracted from this data and data from the literature. By comparing this work to that of CNT, it is possible to correlate a scaling equation that evaluates the inaccessible parameters by connecting nucleation theory to phase diagrams. We are extending this work further by developing a density functional theory approach that should provide a molecular-level understanding of the phase behavior of a polymer/CO_2 system.
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