NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Free volume in contact lens polymersWe have measured the free volume and gas permeability in several contact lens specimens as part of a Space Commercialization Program. Free volume was measured using positron lifetime spectroscopy, while permeability for O2, N2, and CO2 gases was measured using mass spectrometry and polarography. It has been noted that permeability for all gases increases with the mean free volume cell size in the test samples. As might be expected, the specimens with the highest free volume fraction also exhibit the lowest Rockwell Hardness Number. An interesting corollary of this study is the finding that the presence of fluorine atoms in the lens chemical structure inhibits filling up of their free volume cells. This is expected to allow the lenses to breathe freely while in actual use.
Document ID
19930068758
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Singh, Jag J.
(NASA Langley Research Center Hampton, VA, United States)
Eftekhari, Abe
(NASA Langley Research Center Hampton, VA, United States)
Upchurch, Billy T.
(NASA Langley Research Center Hampton, VA, United States)
Burns, Karen S.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 16, 2013
Publication Date
July 1, 1990
Subject Category
Nonmetallic Materials
Meeting Information
Meeting: International Workshop on Positron and Positronium Chemistry, 3rd, Marquette Univ.
Location: Milwaukee, WI
Country: United States
Start Date: July 16, 1990
End Date: July 18, 1990
Accession Number
93A52755
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available