This study presents a novel approach to improve the structure of polymeric nanofibrous aerogels by incorporating silica aerogel particles. Para-aramid nanofibers/polyvinyl alcohol (ANFs/PVA) constitute the skeleton of nanofibrous aerogels, and silica aerogel particles derived from methyltrimethoxysilane (MTMS) serve as structural fulcrums embedded in the skeleton of the aerogels. In order to gain an in-depth understanding of the ANFs/PVA/MTMS composite aerogels, we carefully compared them with MTMS aerogels, ANFs aerogels, and ANFs/PVA aerogels. The preparation process and appearance of above four aerogels were clearly demonstrated. Their macroscopic morphology, chemical composition, and porosity were characterized by field emission scanning electron microscope (FE-SEM), attenuated total reflectance-fourier transform infrared spectra (ATR-FTIR), and nitrogen physical adsorption, respectively. The results show that the silica aerogel particles are firmly embedded in the nanofibrous skeleton of aerogels, effectively resisting volume collapse during gelation and supercritical drying, preserving a finer appearance, and forming a stable ternary nanofibrous structure.

To reinforce the feather resin with Kevlar 29 fibers, the fibers were pretreated with the water-soluble protein derivatives prepared from the waterfowl feathers to cover the outer surface of the fibers. For this purpose, we used aluminum chloride hexahydrate for the pretreatment. When aluminum chloride hexahydrate is hydrolyzed in water, hydrochloric acid and aluminum hydroxide oligomer are generated. The former will work as an etching agent to form small pits or grooves on the fiber surface, and the latter will settle the protein derivatives on the fiber surface through chelate bonding. As a result, we succeeded in generating the insoluble stable coating on the Kevlar 29 fiber surface. This protein coating effectively reduced the photosensitivity of Kevlar 29 to the irradiation with ultraviolet (UV) rays, and fairly prevented the reduction in the tensile strength of the fibers. The photodegradation of Kevlar 29 fibers was found to proceed remarkably in the early stage of the irradiation with UV rays. It also changed the hue of the fibers. The feather resin reinforced with the protein-coated Kevlar 29 fibers exhibited an excellent sonic propagation speed, and a stress transfer coefficient resulted in 0.8 when the law of mixture was applied to the elastic modulus of the composite.