Enhancing mechanical strength and toughness of aramid nanofibers by synergetic interactions of covalent and hydrogen bonding

Aramid nanofibers (ANFs) are outstanding mechanical enhancers of polymers because of the high strength and thermal stability, which also can be processed into macro films through vacuum filtration. However, it is difficult for other additives to improve the mechanical performances of ANFs films except carbon nanotubes (CNT). In this article, polyvinyl alcohol (PVA) and sodium borate (SB) were served as additives to synergistically improve the mechanical performances of ANFs films. It is found that the formed ANFs-PVA-SB ternary composite has a tensile strength of 279.5 MPa and a toughness of 35.7 MJ.m(-3), which are 1.4 and 2.2 times higher than those of neat ANFs films. The high strength is mainly resulted from the fortified hydrogen bonding and physical intertwining between PVA and ANFs, and the formed covalent bonds between PVA and SB, while the high toughness is mainly caused by the soft PVA.