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Effect of NO x environments and stress on degradation of mechanical properties of Kevlar 49 and nylon 6
Author(s) -
Perry M. C.,
Vail M. A.,
Devries K. L.
Publication year - 1995
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760350506
Subject(s) - kevlar , materials science , epoxy , composite material , polymer , nylon 66 , stress (linguistics) , degradation (telecommunications) , curing (chemistry) , polyurethane , amine gas treating , organic chemistry , polyamide , chemistry , telecommunications , linguistics , philosophy , computer science
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. NO 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. NO 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 NO x concentrations at various stress levels. Preliminary studies on the single fibers indicate a stress‐NO 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 NO x concentrations in air as low as 0.1%. We view these effects as having practical technological significance since these lower NO x concentrations approach the level of emissions from exhaust from older model automobiles.