Growing Nano-SiO2 on the Surface of Aramid Fibers Assisted by Supercritical CO2 to Enhance the Thermal Stability, Interfacial Shear Strength, and UV Resistance

Abstract

Aramid fibers (AFs) with their high Young's modulus and tenacity are easy to degrade seriously with ultraviolet (UV) radiation that leads to reduction in their performance, causing premature failure and limiting their outdoor end use. Herein, we report a method to synthesize nano-SiO₂ on AFs surfaces in supercritical carbon dioxide (Sc-CO₂) to simultaneously improve their UV resistance, thermal stability, and interfacial shear strength (IFSS). The effects of different pressures (10, 12, 14, 16 MPa) on the growth of nanoparticles were investigated. The untreated and modified fibers were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It was found that the nano-SiO₂-decorated fibers exhibited improvement of thermal stability and mechanical properties, and the IFSS of the nano-SiO₂ modified fibers increases by up to 64% compared with the untreated fibers. After exposure to 216 h of UV radiation, the AFs-UV shows a less decrease in tensile strength, elongation to break and tensile modulus, retaining only 73%, 91%, and 85% of the pristine AFs, respectively, while those of AFs-SiO₂-14MPa-UV retain 91.5%, 98%, and 95.5%. In short, this study presents a green method for growing nano-SiO₂ on the surface of AFs by Sc-CO₂ to enhance the thermal stability, IFSS, and UV resistance.

Keywords: UV resistance; aramid fiber; interfacial shear strength; nano-SiO2; supercritical CO2; thermal stability.

Figure 1

Set of reaction equipment (a) and schematic diagram of growing nano-SiO₂ on the fiber surface (b).

Figure 2

Simulation diagram of depositing microdroplet on the fiber (a). Images of AF–microdroplet (b) and the debonding device (c).

Figure 3

Infrared spectrum of the untreated and nano-SiO₂-modified fibers.

Figure 4

XRD patterns of the untreated and nano-SiO₂ modified fibers (a). Particle size distributions of nano-SiO₂-14MPa (b).

Figure 5

XPS wide scan of the untreated and SiO₂-modified AFs (a); Si_2p core-level spectra of SiO₂-modified AFs (b).

Figure 6

SEM images: AFs (a); AFs-SiO₂-10MPa (b); AFs-SiO₂-12MPa (c, d); AFs-SiO₂-14MPa (e–g), and AFs-SiO₂-16MPa (h,i).

Figure 7

TGA curves of untreated fibers and modified fibers.

Figure 8

UV–Vis spectra of untreated and SiO₂-treated AFs (a) and their absorbances at 396 nm (b).

Figure 9

Mechanical properties of AFs and nano-SiO₂-modified AFs before (a) and after (b) 216 h of UV radiation.

Figure 10

C1s core-level spectra of AFs and irradiated AFs.

Figure 11

SEM images of the untreated and irradiated AF.

Figure 12

IFSS variation with different embedded lengths of the untreated and nano-SiO₂ modified AF (a) and their values (b).