Effect of NOx environments and stress on degradation of mechanical properties of Kevlar 49 and Nylon 6.: An article from: Polymer Engineering and Science

This digital document is an article from Polymer Engineering and Science, published by Society of Plastics Engineers, Inc. on March 15, 1995. The length of the article is 4039 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

From the author: Mechanical and chemical mechanisms may act synergistically to degrade the mechanical properties of polymers. This synergism should be considered during design of components for sustained loads in hostile environments. If these polymers are to be used as load-bearing structural elements in automobile and industrial environments, they are likely to be simultaneously exposed to such environments and stress. These studies explore the deleterious effects of gaseous pollutants (e.g. N[O.sub.x] in air) and mechanical stress on polymers. This research included studies on nylon-6 and composites of nylon-6 yarns embedded in a bis-A-phenolic resin with an amine curing agent, as well as single fibers and yarns of poly(p-phenylene terephthalamide) (DuPont Kevlar 49) as bare fibers and also embedded in an epoxy matrix. The protective effect of embedding fibers in the epoxy matrix was demonstrated. N[O.sub.x] concentrations were varied between 0 and 1.5%. The sustained loads during exposure were in the range of 50 to 80 percent of the ultimate stress short term load carrying capability of the fibers, Exposure times varied from several minutes to months. Electron spin resonance spectroscopy (ESR) is used in these studies to explore the kinetics of bond rupture and how they relate to the environmental and stress loading histories in nylon. Kevlar 49 degradation studies were conducted by measuring times required for sample failure in N[O.sub.x] concentrations at various stress levels. Preliminary studies on the single fibers indicate a stress-N[O.sub.x] synergism over the range of stresses (48 and 77% of ultimate) and 0.1 and 1.5% gas concentrations. Yarn samples exhibited this synergism over a wide range of stresses (40 to 80% of ultimate). Bare yarn degradation was accelerated by N[O.sub.x] concentrations in air as low as 0.1%. We view these effects as having practical technological significance since these lower N[O.sub.x] concentrations approach the level of emissions from exhaust from older model automobiles.

Citation Details
Title: Effect of NOx environments and stress on degradation of mechanical properties of Kevlar 49 and Nylon 6.
Author: M.C. Perry
Publication:Polymer Engineering and Science (Refereed)
Date: March 15, 1995
Publisher: Society of Plastics Engineers, Inc.
Volume: v35 Issue: n5 Page: p411(8)

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