The effect of the nano-structured aerogel powder on the structural parameters, water repellency, and water vapor/air permeability of a fibrous polyester material

Abstract

A water-glass-based silica aerogel was synthesized through an ambient pressure drying method and its structural parameters, hydrophobic property, and blending with a nanofibrous polyester material were investigated. The hybrid aerogel-fibrous materials were prepared using an electrospinning method and their hydrophobic and water vapor/air permeation characteristics were analyzed using the SPSS software by one-way ANOVA, Duncan, and 1-sample K-S tests. The BET and BJH analyses showed that the nanosilica aerogel has a pore size of 24 nm and a total pore volume of 3.5 m3/g resulted in 88.6% porosity and 0.2 g/m3 density. The silica aerogel granules showed a high water sliding angle, whereas, the aerogel powder-coated water droplets (marbles) showed a sliding angle of as low as 5°. The SEM and AFM analyses indicated the successful embedding of the aerogel powder into the nanofibrous material with an irregular beads–like structure. The most aerogel content of 4 wt% in the hybrid fibrous material showed a lower mean diameter (176.2 nm) as well as a lower mean size of spaces formed between the super-fine fibers (3598.5 nm) in comparison with the fibrous material with no aerogel content. The beaded fibrous structures of the hybrid fibrous materials led to a suitable two-scale surface roughness with an improved water contact angle up to 130.1° in comparison with 103.4° for the one with no aerogel content. The samples surface energy was remained unchanged with 3 M water repellency of 1. Also, there was no significant difference between the water vapor permeability (WVP) of the samples according to the ANOVA tests with P-values of more than 0.05. The super-fine fibers containing 2 and 4% aerogel have a higher permeability to air in comparison to the pure super-fine fibers and the super-fine fibers containing 0.5 and 1% aerogel, which may be due to the recognized effect on the reduction of the fibers diameter as well as smaller empty spaces formed between the super-fine fibers.