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Title: Hydrolytic degradation of Kevlar 49 fibers

Abstract

The hydrolytic degradation of Kevlar 49 fibers and the principal parameters that control this degradation are presented. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration are considered in terms of RH, time, temperature and stress level. The rates of hydrolytic degradation at 100% RH 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 impurities present in Kevlar 49 fibers and their effect on hydrolytic degradation are also discussed. In addition, the aging of Kevlar 49 fibers as a result of exposure to uv and stress are reviewed.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (USA)
OSTI Identifier:
5277278
Report Number(s):
UCRL-89625; CONF-840459-2
ON: DE84004158
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 29. national SAMPE symposium, Reno, NV, USA, 3 Apr 1984
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARAMIDS; FAILURES; HYDROLYSIS; FIBERS; HUMIDITY; 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)

Citation Formats

Morgan, R.J., Pruneda, C.O., Butler, N., Kong, F.M., Caley, L., and Moore, R.L. Hydrolytic degradation of Kevlar 49 fibers. United States: N. p., 1983. Web.
Morgan, R.J., Pruneda, C.O., Butler, N., Kong, F.M., Caley, L., & Moore, R.L. Hydrolytic degradation of Kevlar 49 fibers. United States.
Morgan, R.J., Pruneda, C.O., Butler, N., Kong, F.M., Caley, L., and Moore, R.L. Mon . "Hydrolytic degradation of Kevlar 49 fibers". United States. doi:.
@article{osti_5277278,
title = {Hydrolytic degradation of Kevlar 49 fibers},
author = {Morgan, R.J. and Pruneda, C.O. and Butler, N. and Kong, F.M. and Caley, L. and Moore, R.L.},
abstractNote = {The hydrolytic degradation of Kevlar 49 fibers and the principal parameters that control this degradation are presented. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration are considered in terms of RH, time, temperature and stress level. The rates of hydrolytic degradation at 100% RH 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 impurities present in Kevlar 49 fibers and their effect on hydrolytic degradation are also discussed. In addition, the aging of Kevlar 49 fibers as a result of exposure to uv and stress are reviewed.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Dec 05 00:00:00 EST 1983},
month = {Mon Dec 05 00:00:00 EST 1983}
}

Conference:
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  • 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 aremore » 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.« less
  • Fracture-topography and stress-optical-microscopy are utilized to study the deformation and failure modes of Kevlar 49 fibers and their epoxy composites. Fracture topographies of bare yarns, composite strands, and pressure vessels reveal Kevlar 49 fibers fail in tension by axially splitting 20 to 50 times their diameter D (20 to 50D) along their lengths. This type of fiber failure involves shear-induced microvoid growth throughout the fiber which occurs principally along the fiber axis, followed by macroscopic crack propagation through such microscopic crack propagation through such microvoids. Fiber splitting in the fracture of single filaments is < 5D because of the absencemore » of external shear stresses. The topographies observed in fractured single filaments are described in terms of longitudinal and transverse fiber crack propagation paths in the fiber skin and core. Hydrolytically-degraded Kevlar 49 fibers exhibit lower fiber split lengths in composites. There is a correlation between the percentage of fibers that exhibit transverse failure without splitting and the composite strength. Stress-optical-microscopy studies of the deformation and failure processes of simple composite laminates are reported as a function of laminate geometry, temperature, and fiber surface treatment.« less
  • The impurities in Kevlar 49 fibers (poly(p-phenylene terephthalamide)PPTA) are reported and discussed in terms of the fiber fabrication processes. These impurities were monitored by inductively coupled plasma emission and optical emission spectroscopy. The principal impurities Na/sub 2/SO/sub 4/ and total S were analyzed chemically. From these chemical analyses together with C, N, H elemental analyses we show that there are 1.5 wt % impurities present in Kevlar 49 fibers of which approx. 50% are in the form of Na/sub 2/SO/sub 4/ and the remainder probably in the form of benzene sulfonic -SO/sub 3/H PPTA side groups. There are 3 ofmore » these acid groups per each PPTA macromolecule. Organic impurities, such as terephthalic acid are discussed in the light of degradation studies of PPTA-H/sub 2/SO/sub 4/ spinning dopes. Electron microprobe x-ray spectroscopy and laser-induced damage studies were utilized to investigate the distribution of impurities through the fiber cross-section. The distribution of impurities throughout the fiber are determined by the fiber fabrication processes and are discussed at the microscopic and molecular level. The defects caused by these impurities and their effect on the deformation and failure modes are also considered. 22 references, 3 tables.« less
  • From elemental analyses, thermogravimetric-mass spectroscopy studies and re-evaluation of previous water diffusion studies in Kevlar 49 fibers it is concluded that these fibers can contain two types of sorbed moisture. The fibers can absorb up to approx. 6 wt % loosely bound water with an activation energy for outgassing by desorption of 6 kcal/mole. This loosely bound water is a direct result of the presence of Na/sub 2/SO/sub 4/ impurities and the perturbations they induce on the packing of the rod-like poly (p-phenylene terephthalamide) macromolecules. Kevlar 49 fibers also inherently contain up to 30 wt % additional water which ismore » tightly bound within the crystal lattice. This water exhibits an activation energy for outgassing by diffusion of approx. 40 kcal/mole and is only evolved from the fiber in significant quantities at t > 350/sup 0/C over a period of hours.« less
  • The relation between the physical structure and deformation and failure processes of Kevlar fibers is presented. The fiber fabrication processes that affect the critical structural parameters controlling deformation and failure are considered. The deformation and failure processes are discussed in the light of fracture topography studies of epoxy composite strands and non-etched and HCl-etched bare yarns together with deformation studies of bare yarns deformed directly in the optical microscope. A physical model is suggested for Kelvar 49 in which there is an amorphous skin and crystalline core. The core consists of periodic transverse defect planes spaced about 200 nm alongmore » the fiber. Chain ends are assumed to cluster within the vicinity of these planes. The non-crystalline skin in which the chain ends are arranged essentially randomly relative to one another does not contain such transverse weak planes.« less