Evaluation of the Abilities of Ozone Resistance for Polyamide Fibers: Structures, Properties, and Aging Mechanism

The effects of ozone aging on the structure and related properties of poly(hexamethylene adipamide) (PA66), poly(p-phenylene dodecanediamine) (PA12T), poly(m-phenylene isophthalamide) (PMIA), and poly(p-phenylene terephthalamide) (PPTA) continuous filaments were evaluated. It can be demonstrated that the free radical oxidation reaction occurs in polyamide fibers during ozone aging, resulting in molecular chain degradation, accompanied by color changes. Molecular degradation dominates the subsequent aging process, resulting in decrease in viscosity, mechanical strength, crystallinity, and thermal stability and increase in the formation of oxygen-containing group products. PA66, PA12T, PMIA, and PPTA show different descending trends in their ozone aging resistance, due to the different chemical structures of their molecular main chains. The more stable the generated free radicals are, the higher the ozone aging resistance of the corresponding polyamide is. PPTA has the best ozone aging resistance, followed by PA12T and PMIA, with PA66 being the least aging resistant.