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.