The purpose of the dissertation research was to investigate the effect of cold ammonia gas plasma irradiation on the dyeability of poly(m-phenylene isophthalamide) fibers (Nomex Type 430) with acid dyes. Unmodified Nomex filament yarns were irradiated by ammonia radio frequency glow discharge plasma with constant input power (100 W) and plasma pressure (1 torr) inside the reactor; exposure times were 60, 120 and 180 seconds. The modification in dyeability of plasma irradiated yarns was studied by dyeing with three anthraquinone based acid dyes (C.I. Acid Green 25, C.I. Acid Blue 45, and C.I. Acid Blue 80) and measuring dyebath exhaustion and color strength (K/S) of dyed yarns. The improvement in dyeability of plasma irradiated Nomex filament yarn was investigated by studying the surface chemical composition, surface amine concentration, surface topology, and wettability. Surface chemical composition was analyzed by x-ray photoelectron spectroscopy (XPS). The surface amine concentration was evaluated by studying the plasma amination kinetics through ion-exchange reactions between the ionic dye Ponceau Red 3R and Nomex filament yarn. Surface topology of plasma irradiated filament yarns was studied with high resolution scanning electron microscopy (HR-SEM). The wettability of the irradiated Nomex filament yarns was analyzed in terms of grams of deionized water absorbed per gram of fiber after immersing the yarn specimens in de-ionized water for three time periods (15 s, 30 s, 60 s). The effect of irradiation on the filament yarns’ tensile properties was evaluated by measuring breaking tenacity, elongation at break, and toughness. Statistical analyses of data on various parameters included analysis of variance (ANOVA), orthogonal polynomial contrasts between means, and post-hoc Newman-Keuls tests between means.

XPS spectra showed a higher concentration of both oxygen and nitrogen atoms at the Nomex filament surface after irradiation. Plasma amination kinetics indicated substantially more primary amino functional groups at the filament yarn surface after the plasma irradiation. SEM photomicrographs of plasma irradiated filament yarn indicated surface etching at low magnification (1,600 X) and surface cavitations at higher magnification (25,000 X). The wettability of irradiated Nomex filament yarns with de-ionized water was significantly higher compared to nonirradiated specimens. The dyeability of ammonia plasma irradiated Nomex filament yarns with acid dyes was improved as indicated by higher dyebath exhaustion and higher color strength. The dyebath exhaustion for the three dyes did not vary noticeably with respect to irradiation times (60 s, 120 s, 180 s). Ammonia plasma treatment adversely affected the tensile properties of Nomex filament yarn to a significant extent only after 180 s. Breaking elongation and toughness were more severely affected after 180 s plasma treatment than was the breaking tenacity.