Investigation of sulfonated aromatic compound (SAC) modification to nylon film. 2. Study of SAC sorption isotherm and atomic force microscopic characterization of nylon surfaces

Nylon 6 and nylon 66 films have been treated with aqueous sulfonated aromatic compound (SAC) solutions at concentrations ranging from 0.005 to 1.0 wt%. SAC uptakes at different treatment concentrations were measured and found to follow a BET isotherm. The surface morphologies of nylon film samples, including the original and SAC-treated films, have been characterized by atomic force microscopy (AFM). For untreated nylon 6 and nylon 66 films, AFM images show a randomly distributed fibrillar surface structure. Characteristic widths of fibrils in the nylon 66 and 6 films were 150-225 and 75-150 nm, respectively. For SAC-treated nylon films, the AFM images revealed that the surfaces of the films became covered with nodule-like features having a diameter range of 25-60 nm. AFM analysis provides evidence that SAC treatment deposited a surface coating on nylon films. AFM images of SAC-treated nylon films suggest a mechanism for stain resistance in which the SAC first forms a thin coating on the nylon via bondings between attractive groups in the SAC and nylon polymers. After treatment at increased SAC concentration, the surface is covered with nodule-like deposits which likely serve as a physical barrier to dye permeation. 20 refs., 8 figs.