Construction and characterization of versatile flexible composite nanofibrous aerogels based on thermoplastic polymeric nanofibers

Abstract

Poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers (flexible and effective bonding together) were combined with stiff and flame-resistant sepiolite nanorods (SEP) to fabricate composite nanofibrous aerogels (NFAs) through a versatile and gelation-free freeze-drying method. The PVA-co-PE nanofibers prepared based on a high-yield Melt-Extrusion-Phase-Separation process could form a continuous fibrous structure, and the fibrous networks and surface wettability of composite NFAs could be tuned by the amount of SEP used. The introduction of an appropriate amount of SEP improved mechanical properties of composite aerogels, while excessive SEP would lead to a decrease in compression strength of them. The mechanical properties of composite NFAs are shown to be governed by a combination of stiffness of SEP and effective bonding of PVA-co-PE nanofibers. More importantly, the presence of SEP can substantially improve flame resistance of aerogels. After a simple thermal chemical vapor deposition treatment with methyltrichlorosilane, the surface of composite NFAs become rougher and siloxane nanoparticles became visible. With this deposition, hydrophilic NFAs became hydrophobic as a significant surface property modification. Furthermore, the maximum stress at 60% strain went up from 15.57 to 19.17 kPa and the resilience of composite aerogels improved. Thermal properties results confirmed silane coating can improve the thermal stability and insulation characteristics of polymeric aerogel. The manufactured NFAs are demonstrated as good thermal insulators (0.0274 W m−1 K−1), excellent refractories, efficient water/oil separators (45–108 g/g, 78.58–91.76%) and reusable absorbers. Consequently, the multifunctional silane-coated PVA-co-PE/SEP composite NFAs could be envisaged for several demanding applications.