Erosion of para-aramid fiber caused by ultrasonic treatment

The home made para-aramid fibers and Kevlar49 fibers made by DuPont were subjected to ultrasonic treatment in distilled water and seawater,respectively,varying the treatment durations.The infrared spectrum and viscosity testing were conducted and molecular weight and degree of polymerization of the fibers before and after treatment were calculated.The results showed that both the two kinds of fibers consist of polyphenylene terephthalamide,however,the molecular weight and degree of polymerization of home made para-aramid fibers are lower than those of Kevlar49 fibers.SEM observation and mechanical strength testing found that cracks and fibrillation appeared on the surface of the fibers after ultrasonic treatment,their breaking strength and elongation at break lowered,and the change rate reached the peak values within 24 to 48 hours.Molecular kinetic theory was used to study the loss of fibers′ mechanical strength.