Polypyrrole-coated conductive fabrics

The stabilities of polypyrrole-coated conductive fabrics were highly dependent on the doping counterion as well as the polymerization conditions. The rate of degradation showed a diffusion controlled kinetics at high temperatures. The room temperature half-life for the most stable conductive fabric was estimated to be about five years [129]. 

Kim et al. [133] investigated the EMI shielding performance in 50 MHz to 13.5 GHz frequency range of polypyrrole-coated nylon fabrics. In this study, polypyrrole was electrochemically deposited onto the polypyrrole-coated nylon fabric prepared using the in situ chemical polymerization approach to increase the thermal stabflity and conductivity of the polypyrrole-coated fabric. It was found that the multilayer polypyrrole-coated fabric was better than chemically deposited polypyrrole-coated fabric for EMI shielding. The values for SE were in the range of 5-40 dB depending on the conductivity of the polypyrrole-coated fabric. 

Kincal, D., A. Kumar, A.D. Child, and J.R. Reynolds. 1998. Conductivity switching in polypyrrole-coated textile fabrics as gas sensors. Synth Met 92 53. 

Kaynak, A., and E. Hakansson. 2005. Generating heat fi om conducting polypyrrole-coated PET fabrics. Adv Polymer Tech 24 194. 

The use of resins in conjunction with polypyrrole- or polyaniline-coated fabrics yields composite structures that protect the conductive polymer from oxygen and therefore imparts additional stability to these conductive fabrics. Polypyrrole-coated quartz fabrics embedded in epoxy resins have shown sufficient stability in accelerated aging tests, equivalent to 10 years exposure in the field, to be used in the wings of military aircraft [44]. 

While these studies have shown that polyaniline- and polypyrrole-coated fabrics can behave as chemi-resistive sensors, it is also expected that similar chemi-resistive behavior will be achieved using ICP monofilaments and yams, which are woven or stitched into an existing fabric. Ultimately, vapor detection fabric will need to comprise of an array of sensors with the patterned response fed into a microprocessor in order to identify and determine the concentration of the vapor. The relatively low cost of production and subsequent processing of these electrically conductive fabrics provide the opportunity for designing a textile-based electronic nose, which possess built-in massive redundancy for the sensor array so that device will still function even if there is a localized break (rip, tear hole, etc.) in the fabric network. Specifically, in case some area of the sensor system fads, there is a massive redundancy in the garment such that other areas may stdl be able to acquire the information. This will greatly increase the rehabdity of the system. 

Jakubiec, B., Y. Marois, Z. Zhang, R. Roy, M.-F. Sigot-Luizard, F.J. Dugre, M.W. King, L. Dao, G. Laroche, and R. Guidoin. 1998. In vitro cellular response to polypyrrole-coated woven polyester fabrics Potential benefits of electrical conductivity. J Biomed Mater 41 519. 

Egami, Y, Suzuki. K Tanaka, T Yasuhara, T Higuchi, E and Inoue, H. (2011) Preparation and characterization of conductive fabrics coated imiformly with polypyrrole nanoparticles. Synth. Met., 161, 219-224. 

Highly stable polypyrrole/carbon black Eeonomers can also be synthesized by depositing conductive polypyrrole in situ on carbon black. There is no loss in the conductivity of polypyrrole arbon black Eeonomer after five hours at 300 °C in air (Figure 1). An initial increase in conductivity is observed in the first hour, and the conductivity drops to its original value in the next hour. Similar behavior has been observed for polypyrrole coated fabric at 125 °C (2). 

Many applications of conducting textiles involve the formation of laminates or composites with various thermoset resins such as epoxy, imide, and rubber. The adhesion between the various layers of the composite is a critical factor in the utility of these structures. Only a few papers have addressed the adhesion of polypyrrole-coated fabrics with epoxy resins [44,451. The adhesion at the polypyrrole/textile interface is reasonably strong because of the intermolecular forces between the adsorbed polymer layer and the substrate. The adhesion at the polypyrrole/epoxy interface benefits from the po-... 

Somewhat similar results were reported by Jousse et al. [68], who found that composites made with polyani-line-coated fabrics show only a small increase in the real part of the dielectric constant above that of the base composite made with untreated fabric. They also report that the imaginary part of the permittivity is frequency-dependent as described above. The conductivity of the polyaniline coating appears to be slightly frequency-de-pendent whereas the conductivity of the polypyrrole coating is not frequency-dependent in the range of 10-300 GHz. The broad range of permittivity obtained via the conductivity control enables a variety of absorbing structures to be made. 

Fig. 35.7 Dielectric constant e versus conductivity for polypyrrole coatings on (a) polyester fabric and (b) S-2 glass fabric at 35.27 GHz. (Data from Ref. 71, reprinted by permission of the Society for the Advancement of Material and Process Engineering.)...

Commercially available polypyrrole-coated products from Achilles are predominantly available as coated films, but a number of products based on nonwoven textiles and used as static dissipating bars, brushes, and rollers for photocopying and fax machines are also being offered (see Fig. 35.10). A similar nonwoven material is used in filtration equipment. They also are offering conductive gloves for applications in clean rooms based on a nonwoven fabric constructed of coated polyurethane fibers. 

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