Robust and highly resilient waterborne polyurethane-based composite aerogels prepared by blending with aramid nanofibers

Robust waterborne polyurethane (WPU)-based composite aerogels have a promising prospect of application. However, their preparation is still challenging. Herein, polymerization-induced aramid nanofibers (PANFs) were used to reinforce WPU aerogel by taking the advantage of their intrinsic rigidity and the hydrogen bonding interaction between WPU and PANFs. The WPU/PANF composite aerogels containing 0–10% PANFs were prepared by a simple mixing and freeze-drying technique. The composite aerogels exhibit super-flexibility and excellent processability. The specific compressive strength of the composite aerogels shows an increasing tendency with PANF content. By incorporating 10% PANFs, the compressive strength of the aerogel (WF-10%) reaches 335.1 kPa at 70% strain, which is 742% larger than that of neat WPU aerogel with similar porosity. Cyclic compression tests show that the aerogels have excellent durability with a strain recovery of about 95%. After long-term compressive stress, the WPU/PANF composite aerogels have much better resilience than neat WPU aerogel with similar porosity. In simple burning tests, a continuous char layer was formed on the combustion surface of WF-10%, preventing further combustion.