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Moisture dependence of positron annihilation rates in molecular substancesPositron annihilation rates have been studied in polymers and graphite-polymer composites as a function of their moisture content. The annihilation rates have been found to increase linearly with increasing moisture content in epoxies and polyamides, whereas no definite trends have been observed in polyimides. These experimental results have been used as the basis for the calculation of moisture content of several polymeric test specimens. For example, the directly measured moisture content of a Kevlar specimen was 45.5 + or - 5.0% of saturation value, whereas the moisture content on the basis of the decrease in positron lifetime was calculated to be 46.5 + or - 3.5%. Similarly, the directly measured moisture content of a graphite-epoxy composite (55 v/o fiber) was 19.2 + or - 0.6% of saturation value as opposed to a calculated value of 16.0 + or - 5.0%.
Document ID
19820041680
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Singh, J. J.
(NASA Langley Research Center Hampton, VA, United States)
Holt, W. H.
(NASA Langley Research Center Hampton, VA, United States)
Mock, W., Jr.
(U.S. Navy, Naval Surface Weapons Center Dahlgren, VA, United States)
Date Acquired
August 10, 2013
Publication Date
March 1, 1982
Subject Category
Nuclear And High-Energy Physics
Meeting Information
Meeting: Meeting
Location: Dallas, TX
Start Date: March 8, 1982
End Date: March 12, 1982
Sponsors: American Physical Society
Accession Number
82A25215
Distribution Limits
Public
Copyright
Other

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