Kevlar® and Nomex® modification via 2,4-dihydroxybenzophenone anchoring improves water repellency and induces antibacterial and UV protection properties

Abstract

Aramid materials, such as Kevlar® and Nomex®, are aromatic polyamides exhibiting excellent chemical and mechanical properties. Because of their demanding applications, it is essential to enhance their water repellency, their endurance to UV radiation, as well as their antibacterial properties, while simultaneously preserving or even strengthening their durability. The present work describes the successful modification of aramid materials, in a way that improves the final product, by inducing the desired properties without significantly affecting the existing ones. The synthesis of a model compound simulating aramid materials is carried out followed by thorough studies, thus leading to a better understanding of the behavior of aramid materials at the molecular level, as well as to their optimal modification conditions. Subsequently, the attachment of 2,4-dihydroxybenzophenone to Kevlar® and Nomex® fabrics, using epichlorohydrin as the anchoring moiety, along with detailed characterization, via IR and Raman spectroscopies, thermogravimetric analysis, and SEM imaging, are implemented. The wettability of the modified materials is determined by the water contact angle test, to probe their hydrophilicity or hydrophobicity. The antibacterial protection of the modified aramid materials is determined qualitatively against the Gram-negative bacterium E. coli DH5α and quantitatively according to an in situ method, using cyanobacterium Synechococcus sp. PCC7942. Moreover, the UV protection properties of the modified fabrics are studied by using the UV protection factor (UPF) and average UV-A and UV-B transmittance, while their ultimate strength is found well-preserved.