日光老化及海水老化对PPTA纤维结构及性能的影响

Effect of sunlight aging and seawater aging on structure and properties of PPTA fiber

通过日光老化、海水老化及日光/海水复合老化实验,研究了不同老化方式及老化时间对聚对苯二甲酰对苯二胺(PPTA)纤维表面形貌、化学结构、结晶结构及力学性能的影响。结果表明:随日光老化时间延长,PPTA纤维表面逐渐劣化,分子链中酰胺键发生断裂,结晶度和晶粒尺寸下降,结晶结构被破坏,力学性能呈现先慢后快的下降趋势,日光老化35 d后PPTA纤维的断裂强度和断裂伸长率保留率分别为73.7%和69.2%;海水老化35 d后PPTA纤维表面产生深度较浅的纵向沟壑,大部分集中在纤维皮层;复合老化35 d后PPTA纤维表面纵向沟壑较日光老化35 d时更深,逐渐向PPTA纤维芯层深入;海水老化35 d后纤维的断裂强度和断裂伸长率保留率分别为63.0%和72.4%,日光/海水复合老化35 d后纤维断裂强度和断裂伸长率保留率分别为58.7%和65.9%。

The effects of different aging modes and time on the surface morphology,chemical structure,crystal structure and mechanical properties of poly-p-phenylene terephthamide(PPTA)fibers were studied through sunlight aging,seawater aging and sunlight/seawater composite aging experiments.The results showed that the PPTA fiber surface gradually deteriorated,the amide bonds in the molecular chains broke,the crystallinity and grain size decreased,the crystal structure was destroyed,and the mechanical properties showed a slow to fast decline trend with the prolongation of sunlight aging time;the retention rates of breaking strength and elongation at break of PPTA fiber were 73.7% and 69.2%,respectively,after 35 days of sunlight aging;shallow longitudinal grooves were formed on the surface of PPTA fiber,which mostly concentrated on the fiber skin,after 35 days of seawater aging;the longitudinal grooves on the surface of PPTA fibers after 35 days of composite aging were more profound than those after 35 days of sunlight aging,gradually penetrating into the core layer of PPTA fibers;and the retention rates of breaking strength and elongation at break of the fibers were 63.0% and 72.4%,respectively,after 35 days of seawater aging and were 58.7% and 65.9%,respectively,after 35 days of sunlight/seawater composite aging.