Cell formation in the foaming process of Low-density Polyethylene (LDPE)/p, p-oxybis (benzenesulfonylhydrazide) (OBSH) system was investigated by using a device that could visualize at a constant temperature, and the critical nucleation radius was estimated. The critical nucleation radius was of the order of 10 nm. The cell formation of LDPE foams follows the Boltzmann function, and the high correlation coefficient is as high as 0.9988. Subsequently, the first and second derivatives of cell number vs. time were developed to build a cell formation relationship in the foaming process, which reflects the efficiency and driving force of cell formation and describes these three stages (less-foamed, better-foamed, and over-foamed stage). Hence, the proposed method and estimation of critical nucleation radius can provide a further understanding of the cell formation mechanism in the foaming process.
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