2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
IMPROVING THE PHYSIOLOGICAL FUNCTION OF A BALLISTIC
PROTECTIVE VEST BY SUPERABSORBENT POLYMERS
Volkmar T. Bartels
Hohenstein Institutes, Boennigheim, Germany
Contact person: v.bartels@hohenstein.de
INTRODUCTION
Ballistic protective vests, as they are used in police or military applications, are water vapour
impermeable. Hence, they only offer a limited wear comfort, especially when it comes to
sweating of the wearer, e. g. due to an elevated metabolic rate or a warm environment. On the
other hand, so called superabsorbent polymers (SAPs) are known from hygienic and health
care products (diapers, adult incontinence, sanitary towels etc.). SAPs are polyacrylates,
which are able to absorb a considerable amount of water (many times of their own weight) by
forming gels. In this project, the influence of adding superabsorbent polymers was studied on
the physiological function and especially the moisture management of a ballistic protective
vest, by means of the Hohenstein Skin Model and wearer trials with human subjects. This
work is part of a recent research project on the use of superabsorbent polymers in protective
clothing. A technical report (in German) is available from the author (Bartels 2007).
METHODS
A high-quality ballistic protective vest, as it is used by German policemen, served as the
reference E/5+CO. It contains 40 layers of aramide protective textiles, a cotton jersey as a
sweat absorbing layer and a polyester lining facing the skin. This vest was modified by
substituting the cotton layer by two materials with superabsorbent polymers. Both absorbers
are based on a polyester non-woven with a weight of 60 g/m 2 , which was coated with the
polyacrylates and calendered. E/5+200Kb contains 200 g/m 2 and E/5+400Kb 400 g/m 2 of
superabsorbent polymers. All materials were obtained from German manufacturers.
Materials were investigated by the Skin Model according the following variables: (1) water
vapour absorbency Fi after 1 hour; (2) buffering capacity against vaporous sweat impulses:
here, the relative humidity (rh) below the sample after a simulated vaporous sweat impulse at
time t = 0 was studied; (3) buffering capacity against liquid sweat impulses Kf: the amount of
liquid sweat removed from the skin after 15 min (Kf = 0 no sweat removal, Kf = 1 all sweat
removed).
In addition, wearer trials with human test subjects were performed. Test persons walked at a
speed of 5 km/h for 105 min, and subsequently sat on a chair for another 15 min. Subject
wore a normal clothing ensemble (jeans and shirt). Ambient temperature and humidity were
Ta = 24 °C and rha = 50 %. Relative humidity in the microclimate (rhM) below the ballistic
vest was recorded at 4 different positions. 8 single trials per sample were performed.
RESULTS
In Figure 1 the water vapour absorbency Fi as determined by the Skin Model is shown. It can
be seen that Fi is clearly increased by the use of both superabsorbent compounds E/5+200Kb
and E/5+400Kb in comparison to the reference sample E/5+CO with cotton as absorbing
layer. Whereas E/5+CO is able to take up already a considerable amount of 54 g/m 2 of water
vapour, E/5+200Kb and E/5+400Kb are absorbing 182 and 263 g/m 2 , respectively.
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