Effect of Salt Water Immersion on the Ultimate Tensile Strength of Small Diameter Aramid Braids

Abstract

Small diameter, 1/1 eight-end braids were fabricated using 167 tex Kevlar® 29 yams. Braids, selected at random, were immersed in either distilled or salt water for a period of 30 days and then removed for testing. Half of the samples were tested immediately upon removal, and the other half were allowed to dry at standard con ditions (21°C, 65% relative humidity) for 24 hours and then tested. In addition, another set of braids was left untreated as a control. There were no statistical differences in the strength of braids taken from either the distilled or salt water and tested wet, when compared with each other or the control. The strength of braids immersed in distilled water and tested dry showed a slight but statistically significant increase in strength, but the strength of the braids immersed in salt water and tested dry was approximately 10% lower than that of control. Individual single filaments extracted from dry, untested braids from the treatment groups and the control were subjected to tensile testing. No statistically significant differences in strength were observed between the groups, in dicating that braid strength differences were not due to filament degradation. SEM photomicrographs of dried braids that had been immersed in salt water revealed the presence of interstitial NaCl crystals and clearly showed the deformation of fibers around them. When dried, salt-bearing braids were reimmersed in water and tested wet, there was no strength reduction versus control braids. © 1989, Sage Publications. All rights reserved.