The Influence of Viscosity Ratio on Polypropylene/Polyamide 6 Blend Fibers Irradiated by Ultraviolet Light

Abstract

A study was conducted on the effects of ultraviolet (UV) irradiation by a xenon lamp on the structure and mechanical properties of PP⁄PA6 blend fibers. B-2 blend fibers, which have a viscosity ratio (ηPP⁄ηPA6) lower than 1, show a small dropoff in tensile strength up to 300 hr of irradiation time. However the tensile strength decreases rapidly at 600 hr. In the E-1 blend fiber, which has a viscosity ratio (ηPP⁄ηPA6) higher than 1 and the same PA6 content as in the B-2 blend fiber, tensile strength decreases slightly with UV irradiation.Next, the molecular weight of PP component in blend fiber was measured using GPC. The results indicate that the B-2 blend fiber, having a viscosity ratio (ηPP⁄ηPA6) lower than 1, shows a smaller decrease of molecular weight by UV irradiation than the E-1 blend fiber. These results suggest that in the B-2 blend fiber, the degradation of PP component is controlled, because the two components of B-2 blend fiber are dispersed to disturb the penetration of UV light. Although the tensile strength of B-2 blend fiber decreases more largely with UV irradiation than that of E-1 blend fiber, the molecular weight of PP component in E-1 blend fiber degreases more largely than that in B-2 blend fiber. Since the PA6 component of the E-1 blend fiber is formed as the continuous phase, the decreases in tensile strength and strain of E-1 blend fiber with UV irradiation might be smaller than those of B-2 blend fiber. Moreover, the thermal behaviors of fibers irradiated with UV light were investigated using DSC. Though two endothermic peaks are observed near the melting point of PA6 component in B-2 blend fiber, the endothermic peak at the higher temperature side is lowered by UV irradiation. And the two melting endothermic peaks of the PA6 component change to a single peak. In both blend fibers, the endothermic peak temperature of the PP component is lowered by UV irradiation.