Preparation and properties of micro- and nanocomposites composed of a water-soluble nylon and aramid fibers

Abstract

A commercial 20 wt% solid paste of microfibrillated aramid fibers (MFAs) containing water was treated with potassium hydroxide in dimethyl sulfoxide to produce aramid nanofibers (ANFs). Nanocomposites composed of a water-soluble nylon (A-90, amine-modified poly(ɛ-caprolactam)) and ANFs with fiber contents of 0–5 phr (i.e., parts per hundred resin) were prepared by a casting method of the resin/fiber dispersion in water. A-90/MFA microcomposites were also prepared by the same method for comparison. The FE-SEM analysis revealed that ANFs are much finer than MFAs, and both the fibers are homogeneously dispersed in all the composites. The glass transition and maximum thermal decomposition temperatures of A-90/ANF and A-90/MFA composites were higher than those of A-90. The tensile strength, tensile modulus and elongation at break for A-90/ANF and A-90/MFA composites increased with increasing fiber content. When tensile properties of A-90/ANF and A-90/MFA composites with the same fiber content were compared, A-90/ANF nanocomposites exhibited much better tensile properties than A-90/MFA composites did. Especially, the tensile toughness of A-90/ANF 5 phr was about three times higher than that of A-90.