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Title: Aging studies of Kevlar 49 fibers

The aging mechanisms in service environment of Kevlar 49 fibers, E.I. duPont, (poly(p-phenylene)terephthalamide) are reviewed. The principal aging mechanisms considered are (i) u.v.-, (ii) hydrolytic- and (iii) stress-induced macromolecular chain scission and microvoid growth. U.V.-induced strength degradation can be significant as a result of photo-oxidative and photodegradative radical formation but in Kevlar 49-epoxy composites only the exterior yarn layer is deteriorated. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration is considered in terms of R.H., time, temperature and stress level. The rates of hydrolytic degradation at 100% R.H. in the 100 to 200/sup 0/C range are reported. The estimated rates of fiber degradation in various service environment conditions are also reported and shown not to be serious. The stress-induced aging of Kevlar 49 fibers is considered in terms of the growth and coalescence of inherent microvoids along the fiber axis together with the generation of new microvoids. (These growth processes involve no detectable macromolecular chain scission or deterioration in fiber strength.) At a critical microvoid volume fraction catastrophic failure occurs by interconnection of such voids.
Authors:
; ;
Publication Date:
OSTI Identifier:
5277276
Report Number(s):
UCRL-89971; CONF-840415-6
ON: DE84003001
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 187. national meeting of the American Chemical Society, St. Louis, MO, USA, 8 Apr 1984
Research Org:
Lawrence Livermore National Lab., CA (USA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARAMIDS; AGING; FIBERS; HYDROLYSIS; STRESSES; ULTRAVIOLET RADIATION; CHEMICAL REACTIONS; DECOMPOSITION; ELECTROMAGNETIC RADIATION; LYSIS; MATERIALS; PETROCHEMICALS; PETROLEUM PRODUCTS; PLASTICS; RADIATIONS; SOLVOLYSIS; SYNTHETIC MATERIALS 360405* -- Materials-- Polymers & Plastics-- Degradation & Erosion-- (-1987)