4. Conclusion
We successfully fabricated biomimetic composites with layered “brick-and-mortar” structures using polyimide and MMT through a gravity-induced deposition. This layered structure can effectively block the entry of gases and hinder their diffusion. The WVTR of the composite decreased by 99.18% to 0.0185 g/m2/day and its OTR dropped by three orders of magnitude to 7.98 cm3/m2/day/0.1MPa. Furthermore, this structure can prevent the escape of internal combustible gas, which enables the composite to have excellent flame retardant properties, and the LOI is increased from 47.9% to 67.9%. Benefiting from the low hygroscopicity of polyimide, MMT-PI has better control of water absorption compared to common biomimetic composites. In addition to being used alone as a self-supporting film, it also exhibits excellent flame retardancy when used as a coating. After the PU foam was simply immersed into MMT-PAAS glue and dried from the solvents, the MMT/PAAS-PU had self-extinguishing properties. Its PHRR, THR, and TSP decreased by 53.39%, 40.69%, and 53.03% respectively. This work confirms that the layered structure is effective for the improvement of flame retardancy and expands the polymer family used in the preparation of biomimetic composites. Furthermore, our work provides a simple strategy for the preparation of biomimetic composites with low water absorption, high gas barrier properties, and good flame retardancy, with great application potential in numerous fields.