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Effect of tensile strain, time, and temperature on gas transport in biaxially oriented polystyrene
Author(s) -
Levita Giovanni,
Smith Thor L.
Publication year - 1981
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.760211411
Subject(s) - materials science , xenon , volume (thermodynamics) , polystyrene , argon , strain (injury) , diffusion , ultimate tensile strength , composite material , krypton , strain rate , gaseous diffusion , carbon dioxide , tension (geology) , polymer , thermodynamics , chemistry , organic chemistry , medicine , physics , electrode
The permeability and diffusion coefficients ( P and D ) for gases in a biaxially oriented polystyrene film have been found to increase when a specimen is stretched in simple tension and to decrease with time when the strain is held constant. These effects are attributed, respectively, to an increase in free volume with strain and to the continuous volume recovery (densification) at constant strain. The strain dependence, at small strains, of P and D for Ar, Kr, N 2 , CO 2 , and Xe at 1 atm pressure and 50°C indicates that the size distribution of free‐volume elements is not distorted when a specimen is stretched. At a constant strain of 1.8 percent at 50°C, P and D for xenon decrease about 13.8 and 11.8 percent, respectively, per decade of time—two to threefold faster than for carbon dioxide. These results and those obtained with argon, whose molecular diameter is significantly smaller than that for xenon, suggest that the larger free‐volume elements decrease in size faster than the smaller ones as volume recovery progresses.