Self-Healing Polymer Composites with Enhanced Strength for Use in Protective Textiles

Self-healing materials have the potential to increase the lifetime of products exponentially through both non-reversible healing and reversible healing processes. For instance, non-reversible healing has been demonstrated with the use of micro-spheres filled with healing-compounds used to mitigate micro-crack propagation within materials like concrete or asphalt. Upon use however, micro-sphere rupture is irreversible. Reversible self-healing traditionally is manifested in polymeric or rubber materials designed to exhibit both covalent and ionic bonds within the same material. Reversible self-healing materials not only repair other products but can have extended lifetimes themselves. However, reversible self-healing materials are often mechanically weak when compared to non-reversible self-healing materials, thereby limiting applications. In this work, we aim to improve the strength of reversible self-healing materials for sustainability and to increase the extent of applicable uses of these materials. We hypothesize that through the addition of aramid nanofibers, the mechanical stability of reversable self-healing polymers can be improved.<br/><br/>To produce aramid-reinforced polymer composites, aramid fabric will first be dissolved in dimethyl acetamide and lithium chloride to form nanofibers. The aramid fibers will then be dispersed within a self-healing polymer matrix (previously described by Wang et al. in <i>J. Am. Chem. Soc.</i> 2019) by sonication to randomly align the fibers for enhanced shear and bulk moduli. To determine a preferable fill concentration, aramid will be distributed in a polymer matrix over a range of concentrations. Aramid-reinforced polymers will then be examined for shear strength using an ASTM D 732 punch tool, and the dynamic stress-strain of the materials will be characterized on a split-Hopkinson pressure bar and Charpy impact tester. The reinforced polymer will also be formed into dog bones using a 3D printed mold for determination of the elastic modulus through quasistatic tensile testing. In addition to these tests, ability and time required for the polymer to repair will be monitored over the range of aramid concentrations used.<br/><br/>The primary objective of this work is to provide self-healing textiles with enhanced strength for soldiers in the field to maintain protection following damage of protective gear or uniforms. Following determination of a preferable aramid concentration in a reinforced polymer matrix, the polymer will be electrospun into fibrous textiles for further testing including self-repair following impact, splitting or ripping due to an encounter with a sharp object. Future work hopes to follow self-healing of these reinforced textiles using lab-on-a-chip technologies and determination of how re-use impacts mechanical properties.