Surface properties of structural modified PA 6 fibers

Fine structure, surface properties (electrokinetic properties) and the accessibility of free adsorption groups determine the sorption behavior of fiber-forming polymers. The fine structure of such polymers can be explained using a two-phase model, composed of alternating crystalline and amorphous regions. Different treatments (heat, solutions,...) used in fiber production of finishing processes change the fine structure and surface morphology, causing differences in the accessibility of adsorption places. Distinctions in the sorption capacity of modified polymers occur in this manner. In this paper we have carried out an analysis (using PA 6 fibers as an example) of the interdependence between fiber crystalline structure (density determination and X-ray analysis), surface morphology (using AFM), their electrokinetic character (streaming potential measurements) and their absorption properties (iodine sorption value determination). The structure and adsorption abilities of the PA 6 fibers were modified by annealing in vacuum and treatment in phenol solution. The results show that the modifications for the fibers' fine structure cause changes in both their surface morphology and electrokinetic properties. All these changes are reflected in the different fiber absorption properties. A well-oriented fibril structure toward the fiber axis could be observed on the surface of the raw sample. Following annealing in a vacuum or treatment in phenol solution the surface fibrils joined together and built up wider fibril bounds with hollow places between them. These surface morphology changes are reflected in the different ZP values in plateau. They can be increased by simultaneous decreasing of the adsorption potential values (Phi(Cl-), Phi(K+)) and the iodine sorption values.