Preparation of Polymeric Nanofiber Composites Using Simultaneous Electrospinning/Electrospraying and Their Application to Protective Materials

Abstract

Nanomaterials demonstrate interesting physical and chemical properties compared with conventional materials. Various types of new materials, such as nanoparticle, nanorod, nanosphere and nanofiber, have been investigated. The creation of new functional nanomaterials contributes significantly to the innovation of nanoscience and nanotechnologies. Among them, electrospun nanofibers have been attracting the attention of highly functional materials due to their enhanced properties, such as high surface to volume ratio, very high porosity compared to other conventional fibers. So, nanofibers have been studied for various applications in fields of filtration, tissue engineering, sensor, protective material, electronic and photonic material and drug delivery. In this study, the polymeric nanofiber composites were developed using simultaneous electrospinning/electrospraying, then applied to protective materials. In chapter 2, two types of electrospun polyamide nanofiber composites in which Ag-TiO2 was located either in the interior or on the surface of the nanofiber using electrospinning and simultaneous electrospinning/electrospray (SEE) process, respectively. The performance of the obtained Ag-TiO2-embedded nanofiber composite (interior located Ag-TiO2: AT-in-NF) and Ag-TiO2-decorated nanofiber composite (surface located Ag-TiO2: AT-sur-NF) was compared by evaluating the decolorization of methylene blue (MB) stain and their antimicrobial ability. It was concluded that the positioning of nanomaterial additives is a crucial factor in the enhanced performance of such nanofiber composites, and provide a guide for designing and optimizing nanofiber composites with superior catalytic activities. In chapter 3, a potential application of nanofibrous composite materials impregnated the MgO and POM adsorbents was exhibited as an inner layer for the permeable protective clothing against CWA. The nanofiber composites, which were consisted of both polyamide nanofiber and adsorbents (MgO and POM), were prepared using the SEE process. The nanofiber composites were compared to neat polyamide nanofiber mat by evaluating the permeability of air, moisture and protectability against gas chemical warfare simulants. It was suggested that the high possibility of the application of the nanofiber composites to the inner layer of permeable protective clothing. In chapter 4, it was reported that electrospun meta-aramid nanofibers with enhanced chemical stability and mechanical property using sequential post-treatment for removal of salt in the nanofiber and regeneration of crystalline structure. The aligned meta-aramid nanofibers with LiCl salt was prepared using electrospinning apparatus with drum-collector. The washing and heating sequential post-treated nanofiber mats showed improved chemicals stability. Furthermore, in order to estimate the possibility of their application to an outer layer for permeable protective clothing having the repellency against liquid chemical warfare simulants, the surface of meta-aramid nanofibers was modified via treatment using water and oil repellent. In chapter 5, lightweight nanofibrous assemblies with high protection ability against chemical warfare agents (CWAs) were developed using laminated outer and inner layers based on aromatic and aliphatic polyamide nanofiber composites with CWA adsorbents magnesium oxide and polyoxometalate. Thickness, weight density (weight per area), cool/warm feeling and air/moisture permeability of the assembly were compared with the permeable protective clothing of Korea Army as a reference. The thickness and weight density were variated according to the number of stacking, and finally, the lightweight assemblies with high protectability against CWA can be developed. The assembly surpassed the reference in the cool feeling property, and provided good resistance to the penetration of chemical warfare agents in gas form, while still allowing significant water vapor transmission to promote evaporate cooling of the body. The development of the assembly suggests new approach to improving performance of a permeable protective materials, and provides a guide for designing and optimizing the permeable protective clothing.