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Effect of polymeric structure on the permeation rate in standard reference material sulfur dioxide permeation tubes
Author(s) -
Reneker D. H.,
Martin G. M.,
Rubin R. J.,
Colson J. P.
Publication year - 1975
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.760150103
Subject(s) - permeation , materials science , polymer , lamellar structure , tube (container) , chemical engineering , composite material , analytical chemistry (journal) , membrane , chromatography , chemistry , biochemistry , engineering
Liquid SO 2 sealed into tubes made of a fluorocarbon copolymer permeates the walls of the tube at a temperature‐dependent but accurately reproducible rate. Sulfur dioxide dispensers made in this way are called permeation tubes and are useful for calibrating instruments that measure SO 2 concentrations in air. The National Bureau of Standards calibrates SO 2 permeation tubes and makes them available as Standard Reference Materials. The permeation rate in a batch of nominally identical tubes varies enough that each Standard Reference Material tube must be individually calibrated. Changes in the length or radial dimensions of the tubes are much too small to explain most of this variation. An excellent (negative) correlation is found between the measured permeation rate and the density of the polymer (or weight per unit length). Since both the measured density and the permeation rate for this semi‐crystalline polymer depend upon morphological factors, but in different ways, x‐ray diffraction measurements of the thickness and orientation of the lamellar crystals were made and a mathematical model was set up to identify the morphological factors which can cause variations in the permeation rate.