A comprehensive review of cell structure variation and general rules for polymer microcellular foams

The cell structure variation in polymer microcellular foams and the general rules for cell structure control are systematically reviewed. First, the three parameters that characterize the cell structure are considered to be the cell size, cell density and expansion ratio. Second, based on increase or decrease of these three parameters, the cell structure variation is classified into six types. Each type is thoroughly discussed as a function of the influencing factors. Third, the relationships between cell structure and properties, including mechanical properties and thermal insulation, are discussed. Fourth, the general rules for cell structure control are proposed. Fifth, the issues worthy of in-depth study are comprehensively discussed.