T29-025
DIFFUSION PROCESS OF CHEMICAL AGENTS IN BARRIER POLYMERS AS A KEY FACTOR OF
DECONTAMINATION EFFICIENCY
Jiri Slabotinsky, Stanislav Bradka, Pavel Castulik*
National Institute for Nuclear, Biological and Chemical Protection v.v.i., Kamenna 79, 262 31 Milin, Czech Republic, www.sujchbo.cz
*CBRN Consultant, Mikulaskovo sq. 17, 625 00 Brno, Czech Republic E-mail: pcastulik@yahoo.co.uk
ABSTRACT
Chemical Warfare Agents (CWA) and/or Toxic Industrial Chemicals (TIC) can
contaminate protective barrier materials made of polymer basis. Chemical molecules
permeate and penetrate into the depth of majority barrier material through diffusion
process. Despite the removal of liquid portion of a chemical from external surface of
barrier material, diffusion process of a chemical continues also in reverse direction,
back towards original surface. This reversible secondary contamination of the surface
creates further delayed safe contact and representing off-gassing hazards. The
objective of the research was to describe the mechanism and conditions of selected
chemicals permeation through and out of polymer material after its surface
decontamination. Outcomes of the research can be utilized also in advanced studies
for CWA dermal permeation and skin effective decontamination.
MATERIAL AND METHODS
Polymer membranes of polyethylene (PE) and butyl rubber (IIR) used for
manufacturing of PPE had been exposed with S-Mustard agent (HD 90% of purity),
dichlorhexan (DCH), and the mixture of HD 90% and DCH 10% in permeation cell,
under define temperature and time exposure. The access of chemical agents after
define exposure of a membrane had been removed from its exposed surface by
decontamination with ethanol or sodium hypochlorite (5% solution for 5 min. of
exposure, drying with swab, washed with distilled water and drying with swab) or with
powdered active charcoal and/or bentonite (thickness of layer 1 mm). Thorough
decontamination of swatches was done in boiling solution of 2% bicarbonate for 2
hours.
Permeation and desorption of the chemicals with membranes was monitored through
colorimetric contact detection and gas chromatography, in order to identify surface
decontamination efficiency and desorption process afterwards.
RESULTS AND DISCUSSION
Study demonstrates reversible diffusion of chemical substances from exposed barrier protection
materials even after thorough surface decontamination. The level of internal contamination of
barrier material depends on their resistance characteristics (resistance/breakthrough time) and
such as thickness of barrier material, diffusion coefficient, solid/polymer solubility, temperature,
time of exposure and physical/chemical properties of challenging chemicals.
Permeation and diffusion process of liquid agent in polymer matrix is controlled according
Fick Law, where:
F is velocity of sorption and desorption [g.cm-2.s-1]
D is diffusion coefficient [cm2.s-1]
C1 is concentration of agent on surface of a barrier [g.cm-3]
C2 is concentration inside of a barrier [g.cm-3]
h is thickness of a barrier in [cm]
Diffusion process is also controlled through ambient temperature according Arrhenius formula,
where:
D0 is frequency factor
ED is diffusion activation energy
R is gas constant
T is absolute temperature
Water based decontamination mixtures and dry sorbents are enabling to remove liquid
contamination only from the surface of polymer matrixes. Hydrophobic and non-porous polymer
surface prevents interaction of chemically active water based solution with the chemical
contaminant already permeated into the mass of polymer material. In both cases of polymer
material decontamination there is continuing reversible diffusion process, resulting in release of
absorbed contaminant back onto decontaminated surface. Diluted HD with 10% of DCH causes
faster desorption of HD from the IIR polymer matrix. Physical decontamination with EtOH
remains threshold of the agent on the surface of polymer matrix and which is accompanied with
sub sequential desorption of the agent. In the case of decontamination with chemically active
mixture, such as solution of NaClO the efficiency of decontamination is significantly higher and
reducing also following desorption of the agent. However, reaction products might slowdown
and prolong desorption of the agent in comparison with only physical dilution and removal the
agent with EtOH. Satisfactory decontamination of HD at the IIR type matrix can be achieved in
hot chemically active decontamination solution, when temperature speed up the process of
reverse diffusion and support also chemical reaction with a contaminant.
h
CC
DF 21 

RT
ED
eDD

 0
CONCLUSIONS
Diffusion of chemical liquid contaminants into barrier protection material represents potential hazards of secondary contamination after surface
decontamination was performed. Serious concern has to be given to potential cases, when additional solvent(s) with CWA and/or TIC can be used to
accelerate permeation, due to the process of reverse diffusion through barrier protective materials and thus challenging protective properties of
personal protective ensemble. Currently used different barrier material for PPE should be evaluated against mixtures of CWAs with selected solvents as
“vehiculum” of penetration to polymer matrixes and accelerating also desorption of agents. Mathematical apparatus describing diffusion and
permeation processes through polymer membranes can be used for prediction purposes and comparative studies for modeling of dermal exposure and
skin decontamination. Actual decontamination efficiency can be determined based on further experimental and modeling research results.
0
10
20
30
40
50
60
70
0 5 10 15 20 25 30 35 40 45
BreakthroughTime[min]
Droplet Exposure Time [min]
Breakthrough Time of HD through PE Membrane
HD droplet 1ml @ 20ºC, hPE = 0,010 cm; droplets decontaminated after
exposure time with active charcoal and bentonite
Active
Charcoal
Bentonite
0
100
200
300
400
500
600
0 10 20 30 40 50
Qmax[μg/cm2]
Exposure Time of Droplets [min]
Quantity of HD Permeation Through PE Membrane
Droplets Drained and Adsorbed(covered) with Bentonite
1 μl HD droplet @ 20°C hPE =0,01 cm
droplet
drained
droplet
adsorbed
0
20
40
60
80
100
120
140
160
0 20 40 60 80 100 120 140 160 180
ConcentrationHD[ppm]
Desorption Time [min]
Desorption of HD from IIR Membrane
HD droplets 3x0,5μl @ 24,5°C; exposure 2 hours;
hIIR = 0,048cm
decontamination with EtOH decontamination with NaOCl
0,00
500,00
1000,00
1500,00
2000,00
2500,00
3000,00
0 50 100 150 200 250 300
Concentration[μg.m-3]
Desorption time [min]
Desorption of neat HD, DCH and mixture of 10%DCH/90% from
IIR membrane
Droplets 1μl@ 25°C;hIIR = 0,048cm, exposure 10 min
dichlorhexan neat HD neat dichlorhexan from mixture 10%DCH/90%HD HD from mixture 10% DCH/90% HD
-50
0
50
100
150
200
0 10 20 30 40 50 60 70 80 90
Qmax[mg/cm2]
Time of Permeation [min]
HD Permeation Through PE Membrane
HD Droplets Removed after Different Exposure Time
Droplet 5 μl@30°C; hPE =0,01 cm
Exp 5 min
Exp 10 min
Exp 15 min
Exp 20 min
Exp 30 min
AFTER
BOILING DECONTAMINATION
AFTER
ETHANOL DECONTAMINATION