Ultra-light, super-insulating, and strong polystyrene/carbon nanofiber nanocomposite foams fabricated by microcellular foaming

Energy management plays a critical role in energy saving and environment protection by reducing energy waste. High-performance thermally-insulating materials, as an effective strategy of thermal management, have received widespread attention in industrial and academic field. Owing to the ever-increasing requirements for thermal insulation and mechanical performance, conventional insulation materials are currently encountering bottlenecks. Herein, ultralight, super-insulating, and strong polystyrene (PS)/carbon nanofiber (CNF) nanocomposite foams were fabricated by using flexible and environmentally-friendly microcellular foaming with CO2 as blowing agents. Thanks to CNFs' strong infrared absorption and CNF-induced unique cellular morphology, the achieved ultralight PS/CNF foam exhibited outstanding thermally-insulating performance with a thermal conductivity as low as 26.7 mW/m·K, which, to our best knowledge, is the lowest value for PS foams without using any insulation gas. Furthermore, the PS/CNF nanocomposite foam also showed excellent mechanical properties with a compressive strength of 0.96 MPa, 174% higher than the pure PS foams, mainly attributed to the stiff nature of CNFs. Thereby, this cost-efficient, scalable, and green process to manufacture ultralight and strong PS foams with unexpected insulation properties could greatly broaden potential applications of commonly used polymers as advanced thermally insulating materials.