Development of nanocomposite nanofiber materials production for ballistic applications

In this study, poly (p-phenylene terephthalamide) (PPTA) polymer, which is frequently used in body armor applications due to its high performance in terms of tensile strength, thermal stability and weight saving, was synthesized. N-butyl PPTA polymer was obtained with the modification of the synthesized PPTA by the N-alkylation reaction in order to eliminate the processing difficulties such as insolubility in common organic solvents and incapability of processing by common thermoplastic processing methods due to the high transition temperature. The chemical structures of the synthesized polymers were confirmed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance spectroscopy (13C-NMR) and X-ray diffraction method (XRD), and it was determined that the butyl groups were grafted onto the PPTA chains with the substitution degrees (DS) of 93-96%. N-Butyl PPTA was found to be soluble in some common solvents at room temperature as a result of the solubility tests, added into polyacrylonitrile (PAN) matrix in solution and nanocomposite nanofiber films with different N-butyl PPTA contents were fabricated by the electrospinning method. FTIR analysis showed that hydrogen bonding interactions occurred between the polymer components in the nanocomposite structure. Scanning electron microscopy micrographs demonstrated that the nanocomposite nanofiber films consist of more homogeneous nanofibers without any beady structures and have a narrower diameter distribution compared to the neat PAN nanofiber films. Mechanical tests showed that the tensile strength increased by 119% and the elongation at break increased by 266% with 3% N-butyl PPTA content by mass compared to the neat PAN nanofiber films. The fabricated nanocomposite nanofiber films were combined with aramid fabrics to produce laminated hybrid composite armors in different configurations and the ballistic tests were performed according to the NATO Stanag 2920 standard. The ballistic tests showed that concentration of the kinetic energy of the bullet in a narrow area was prevented due to the high surface area/mass ratio (average fiber diameter: 598 nm) of the nanocomposite nanofiber films and the ballistic limit velocity (V50) was enhanced with a very small mass increase.