▎ 摘　　要

Previous preparation of nanocellular thermoplastic polyurethane (TPU)-based foams was at low foaming temperature and so long saturation time is needed. In this work, nanocellular structure with high cell density (up to 2.52 x 10(12) cells/cm(3)) is developed by foaming TPU nanocomposites with 0.5 and 0.75 vol% reduced graphene oxide (rGO) at higher foaming temperatures. The formation of such nanocellular structure is ascribed to appropriately higher elasticity and obviously higher melt strength of the TPU nanocomposites, which result from a percolation structure of well exfoliated and dispersed rGO layers and the higher temperature. The nanocellular TPU nanocomposite foams with high cell density exhibit obviously higher dielectric permittivity value in low frequency range, which is ascribed to enhanced interfacial polarizations because of higher rGO content and possible dielectric breakdown of gas in large numbers of the nano-sized cells.