Poly(vinyl alcohol) Composite Aerogel toward Lightweight, Remarkable Flame Retardancy, and Thermal Insulation Properties by Incorporating Carbon Nanohorns and Phytic Acid

In this work, an aerogel with excellent flame retardancy, enhanced compression modulus, and efficient thermal insulation was developed from poly(vinyl alcohol) (PVA), biobased phytic acid (PA), and single-walled carbon nanohorns (SWCNHs). The microstructural evolution of the freeze-dried PVA/PA/SWCNH composite aerogels revealed that varied amounts of phytic acid could influence the three-dimensional architecture. Especially, when the concentration of PA was 1.5%, the PVA/PA/SWCNHs composite aerogel with a tightly arranged "short tubes" structure had a high compressive modulus of 2.02 MPa, corresponding to the specific modulus of 20.2 MPa cm3/g. Compared to the PVA/SWCNHs aerogel, the PVA/PA/SWCNHs composite aerogels showed better fire retardancy, as confirmed by limited oxygen index (LOI) tests and cone calorimetry (CC) tests. Notably, the introduction of phytic acid at 1.5% resulted in LOI values up to 49.8 ± 0.1% and the pHRR and THR of the PVA/PA/SWCNHs composite aerogel were dramatically reduced by 74.3 and 81.0%, respectively. In addition, PVA/PA/SWCNHs composite aerogels with different concentrations of phytic acid exhibited excellent thermal insulation performance with a slightly lower thermal conductivity (32.2–46.9 mW/(m K)) and resisted the ∼1300 °C flame. Meanwhile, the synergistic flame retardancy between SWCNHs and phytic acid was also confirmed by the analysis of the char residues and gas-phase products. These unique characteristics make the aerogel a promising multifunctional candidate for applications in aviation, aerospace, and other fields.