Maintaining comfort levels and protection from arctic cold weather has been an ongoing need in military clothing. Current garment systems are problematic due to overdressing, moisture from sweat, discomfort following strenuous activity, and loss of manual dexterity. These challenges must be balanced in an effort to improve dexterity and mobility while reducing hypothermia and frostbite. Our effort is focused on developing two textile coatings containing silver nanowires (AgNWs) and thermo-responsive hydrogels, which in tandem aim to maintain thermal comfort. AgNWs coatings provide thermal insulation through increased infrared (IR) heat retention as well as active heating due conductive properties of the nanowires. The hydrogel coating provides comfort by increasing the textile’s wicking capability and reversibly storing moisture. AgNWs were prepared by reducing silver nitrate with ethylene glycol (EG) in the presence of silver seeds and polyvinyl pyrrolidone. AgNW nucleation was assessed through optical microscopy. Fabric of different materials were dip-coated with the nanowire ink and the thermal properties were examined. Scanning electron microscopy and Fourier Transform Infrared Spectroscopy revealed a conductive network of silver nanowires (~105 nm diam.) that were highly thermally insulating with a reflectance of &gt;24% observed for 100% cotton indicating that AgNW-cloth is an effective IR reflector suitable for personal thermal management. Joule heating experiments revealed that the temperature of the AgNW-coated textile could be increased by ~109 °C after applying 3 Volts across the fabric. Thermal images were also investigated and thermal radiation of fabric coated with AgNW ink was decreased by ~3°C resulting in textiles appearing colder. Finally, spacing between AgNWs was determined at ~500 nm suggesting that breathability of the textile was not compromised. Concurrently, efforts are also focused on hydrogel coatings and their behavior after exposure to low temperatures. Three polymer systems –poly (N-isopropylacrylamide), polyethyleneglycol, and poly acrylic acid—were studied for changes in morphology and absorptivity after exposure to – 80 ° C. The gels were able to absorb a significant percentage of water after cold treatment. Further studies aim to optimize coating adherence to textiles and durability. Our developed textile coatings could efficiently provide protection from extreme climatic operating environments.

Improvement of personal thermal management by electrically conductive silver nanowire-hydrogel textile coatings

256th National Meeting (2018)

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