EFFECT OF HEAT TREATMENT ON DYEABILITY, GLASS TRANSITION TEMPERATURE, AND TENSILE PROPERTIES OF POLYACRYLONITRILE FIBERS (ORLON 42) (SHRINKAGE, INFRARED, MORPHOLOGY)

Acrylic filament fibers (DuPont Orlon 42 Tow) were subjected to a series of heat treatments consisting of dry heat at 110(DEGREES)C and 150(DEGREES)C and to saturated steam at 110(DEGREES)C for periods of 5 minutes; samples were exposed both under tension of 0.025 grams/denier and slack (no tension). Following the heat treatments, physical and chemical properties of fibers were determined.; Deniers of treated and untreated fibers were determined and the results were used in calculations of tenacity and initial modulus. Tensile properties were measured on a constant-rate-of-extension machine. Shrinkage of treated and untreated fibers were measured after they were boiled in water for 15 min. The glass transition temperatures (Tg) were obtained by differential scanning calorimetry. The ratio of the intensities of the CN/CH stretching bands were found by infrared spectroscopy, using the KBr method.; Dye uptake was measured spectrophotometrically, using filtered solutions of fiber which had been dyed with C. I. Basic Red 18 from an infinite dyebath for 15 minutes at the boil.; Physical properties (tenacity, elongation, initial modulus and shrinkage) were found to be affected primarily by the presence or absence of tension during heat treatment. That is, the temperature of dry heat and the presence or absence of moisture at 110(DEGREES)C had less effect. Chemical properties (Tg and dye uptake) responded to treatment in a less clearcut fashion. Heat treatment with moisture at 110(DEGREES)C, both slack and under tension, produced the highest values of Tg. Moist heat at 110(DEGREES)C, slack, gave the highest dye uptake while treatment at 150(DEGREES)C, dry under tension, produced the lowest dye uptake. Nitrile group association was found to be statistically unaffected by treatment, but the values found correlated well with Tg and dye uptake results. These results were interpreted as supporting the theory that both free volume and pore mechanisms are operative in the dyeing of acrylic fibers.