This paper deals with results from a feasibility study initiated by the U.S. Coast Guard under Contract DTCG39-85-R-80272 on Radioactive Tracers in Permeation Studies.
Permeation tests using 14C-labeled permeant chemicals have been performed according to ASTM Test Method for Resistance of Protective Clothing Materials to Permeation by Hazardous Liquid Chemicals (F 739-81). The method has included water as the collecting medium, discrete sampling with replenishment, and counting of the samples with liquid scintillation counting. Tests with Viton/chlorobutyl laminate on polyester support and acetone as permeant plus neoprene and nitrobenzene are reported. Due to a high sensitivity, breakthrough is seen in both cases in the first samples, that is, after 2 min for Viton/chlorobutyl laminate/acetone and after 2 s for neoprene/nitrobenzene. Steady-state permeation rate is achieved after 3.5 h at 0.49 mg/m2/s1, and 1 and 0.3 h at 5.93 mg/m2/s1 for the Viton/chlorobutyl laminate/acetone system and the neoprene/nitrobenzene system, respectively.
For the Viton/chlorobutyl laminate/acetone system, the propagation versus time of the permeant front inside the membrane has been visualized by autoradiography using a freezing technique and a cryomicrotome.
An autoradiographic calibration technique has been developed and applied giving the absolute concentration (mg/g) versus depth in microns from the exposed side of the membranes.
The tracer technique in combination with dry combustion has been applied to well-known decontamination procedures with the neoprene/nitrobenzene system. After thermal treatment, a residual amount of 0.08% nitrobenzene was found, implying a decontamination efficiency of 99.9%.