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Shelby Mallin1 Curtis Baker2 Ronda Coguill2 Hugh Craig3 Jack Skinner4 Dario Prieto1

1, Montana Tech, Butte, Montana, United States
2, Montana Tech, Butte, Montana, United States
3, Sp2Nano, Butte, Montana, United States
4, Montana Tech, Butte, Montana, United States

Woven fabrics of para-aramid fibers, such as Kevlar and Twaron, are widely used in body-armor applications, but they are limited to shrapnel and small-caliber ratings. These fibers typically fail due to breakage of hydrogen bonds between polymer chains. Cross-linking solves this issue, but results in fabrics less pliable, less breathable, and less suitable for wearable applications. Herein, we present a simple method to enhance the mechanic and ballistic properties of woven para-aramid fibers without compromising their desirable qualities. First, multiwall, carboxyl-functionalized carbon nanotubes (CNTs) dispersed in toluene are functionalized with toluene diisocyanate (TDI). Then, carboxyl or amine functionalized para-aramid fabrics are treated with the TDI-CNT dispersion, which results in CNT loadings up to 6 wt%. The addition of CNTs produces modest tensile strength increases (~5 %) and significant increases in single yarn pull-out strength (190 %). This behavior is indicative of increased entanglement—greater difficulty in fibers sliding past one another, but not in moving together. The modified fabrics are also subjected to two types of ballistic tests using projectiles of 2.6 g and 215 m/s. Single layers of fabric dissipate up to 80 % more kinetic energy following the addition of CNTs. Similarly, five layers of fabric result in up to 50 % lower back-face deformation of ballistic clay following the addition of CNTs. These significant enhancements not only enable lighter and stronger body armor, but they also expand the potential applicatons of para-aramids.

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