One-step and green synthesis of lightweight, mechanically flexible and flame-retardant polydimethylsiloxane foam nanocomposites via surface-assembling ultralow content of graphene derivative

Lightweight polydimethylsiloxane (PDMS) foam materials with outstanding mechanical flexibility and high-temperature stability as well as excellent flame resistance are attractive for various potential applications. However, incorporation of conventional flame retardants needs high filling content and usually induces compromise of other important performance, limiting their practical application significantly. In addition, the problems of complicated procedure and environmental pollution of the traditional processing are imperative but challenging. Here, we report a facile and green in-situ surface-assembly approach to construct two types of graphene oxide (GO) derivative (i.e. sheet and nanoribbon) coatings bonded onto the PDMS foam surface and investigate their discrepancies in thermal and mechanical and flame-retardant properties of the two nanocomposite systems. Interestingly, surface-assembling ultralow loading (<= 0.10 wt%) of two GO derivatives can produce significant improvements in thermal stability and flame retardancy of the PDMS foam without affecting its density and elasticity. Typically, similar to 31% and similar to 40% reduction in peak heat release rate and similar to 80% and similar to 95% improvement in total smoke release were achieved for 0.10 wt% GONR and GO sheet, respectively. Based on the burnt surface zone observation and analysis, the synergistic flame-retardant mechanisms and their differences between the PDMS molecules and two GO derivatives were discussed and clarified. This work provides a new understanding for design and development of green and large-scale fabrication of flame retardant PDMS foam nanocomposite materials.