Chemical Protective Materials Research Articles

Preparation of Polymer Composite Selective Permeable Membrane with Graphene Oxide and Application for Chemical Protective Clothing

Chemical warfare agents (CWA) can poison people through the skin and cause injury, and the use of chemical protective clothing (CPC) is an important way to protect personnel from injury. CPC performance strongly depends on chemical protective materials, and satisfactory protective materials must meet various requirements, including protective performance, physiological comfort, mechanical performance, and cost effectiveness. Here, low-cost materials were used to prepare PVDF sodium sulfonate composite membranes with different contents of modified graphene oxide (GO-SSS). Their tensile properties, contact angle, permeability, and selectivity were tested and analyzed. The results show that when the addition ratio of GO-SSS to the bare membrane is 0.5%, the composite membrane has desirable permeation selectivity of water vapor/CWA simulant vapor and desirable mechanical properties. Hence, our sodium sulfonate composite membrane of PVDF with GO-SSS is an ideal material for potential applications in CPC.

Nanoflake-Engineered Zirconic Fibrous Aerogels with Parallel-Arrayed Conduits for Fast Nerve Agent Degradation.

Chemical warfare agents (CWAs) pose huge threats to ecological environments, agriculture, and human health due to the turbulent international situation in contemporary society. Zirconium hydroxide (Zr(OH)4) has captured the prime focus as an effective candidate for CWA decomposition but is often hindered by the isolated powder form. Here, we demonstrate a scalable three-dimensional space-confined synthetic strategy to fabricate nanoflake-engineered zirconic fibrous aerogels (NZFAs). Our strategy enables the stereoscopic Zr(OH)4 nanoflakes vertically and evenly in situ grown on the interconnected fibrous framework, remarkably enlarging the surface area and providing rich active sites for CWA catalysis. The as-synthesized NZFAs exhibit intriguing properties of ultralow density (>0.37 mg cm-3), shape-memory behavior under 90% strain, and robust fatigue resistance over 106 compression cycles at 40% strain. Meanwhile, the high air permeability, prominent adsorptivity, and reusability make them state-of-the-art chemical protective materials. This work may provide an avenue for developing next-generation aerogel-based catalysts and beyond.

Molecular Cage-Mediated Radial Gradient Porous Sponge Nanofiber for Selective Adsorption of a Mustard Gas Simulant.

Poisons and poisonous weapons in armed conflict, especially chemical warfare agents (CWAs), pose serious threats to global security. Porous materials have recently been regarded as promising candidates to defend personnel in a CWA-contaminated environment, but challenges remain for integrating these materials into protective garments without sacrificing the intrinsic flexibility of fibers. Here, we report a rigid-flexible coupling hypercross-linking methodology to create flexible sponge-like nanofibers featuring hierarchical radial gradient porous nanoarchitectures, in which the inner structure is a mesoporous multichambered network, and the outer structure is a dense domain with a microporous network structure. Experimental and computational evidence supports the contention that sponge nanofibers with distinctive pore topology and robust bendability can be designed by manipulating the flexibility of building blocks. The resulting heterogeneous nanofibers exhibit integrated properties of spatially selective superstructures, abundant micropores, interconnected mesopores, a high surface area (579 m2 g-1), remarkable flexibility, and exceptional CWA affinity, which are extraordinarily effective for adsorptive performance (498 mg g-1). The successful synthesis of these materials might inspire the development of chemical protective materials in an efficient, self-standing, and structurally adaptive form.

Preparation and Chemical Protective Clothing Application of PVDF Based Sodium Sulfonate Membrane.

Chemical protective clothing (CPC) is major equipment to protect human skin from hazardous chemical warfare agents (CWAs), especially nerve agents and blister agents. CPC performance is mainly dominated by the chemical protective material, which needs to meet various requirements, such as mechanical robustness, protective properties, physiological comfort, cost-effectiveness, and dimensional stability. In this study, polyvinylidene fluoride (PVDF) based sodium sulfonate membranes with different ion exchange capacities (IECs) are prepared simply from low-cost materials. Their mechanical properties, contact angles, permeations, and selectivities have been tested and compared with each other. Results show that membranes with IEC in the range of 1.5–2 mmol g−1 have high selectivities of water vapor permeation over CWA simulant vapor permeation and good mechanical properties. Therefore, PVDF-based sodium sulfonate membranes are potential materials for CPC applications.

Reactivity and reusability of immobilized zinc oxide nanoparticles in fibers on methyl parathion decontamination

Zinc oxide (ZnO) nanoparticles were used as the photocatalyst to develop self-decontaminating fibers for potential use as chemical protective materials. Since ZnO is an effective photocatalyst for degradation of organophosphate, it was incorporated in electrospun polyacrylonitrile (PAN) fibers. Photocatalytic degradation of methyl parathion, an organophosphate, upon exposure to ZnO-PAN fibers was evaluated and found to be effective for reuse for up to five exposure cycles. High performance liquid chromatography, UV-vis spectroscopy, calculations of octanol–water partition coefficients, and 31P NMR spectroscopy were used to determine that hydrolysis is the probably mechanism for photocatalytic degradation.

Performance-based design of permeation test cells for reliable evaluation of chemical protective materials

The test cell constitutes the core functionality of a permeation testing system. Accuracy of an experimental methodology depends on the ability of the test cell to efficiently deliver the challenge agents to the test material, collect all the transported permeate compounds from the test material and transfer those analytes to the online detector. Common test cell designs used in the US and internationally form the basis of their respective testing procedures. However, widespread usage does not necessarily equate to defensible assurance of analytical reliability. Consequently, chemical protective materials characterized with these cells may provide inadequate protection to users whose health and safety depend on barrier garments such as gloves and suits. Permeation test data, including those acquired in our laboratory, have emphasized the significance of test cell design on the accuracy of permeation measurements. This paper describes the key considerations necessary to ensure analytical reliability for a test cell, illustrates quantitative improvements demonstrated by existing prototypes and, finally, proposes a design which further advances the technology of permeation testing.

Design and Performance of an Integrated Analytical Swatch Testing System

An integrated swatch testing system for precisely quantifying the resistance of chemical protective materials to permeation and penetration by a chemical weapons agent (CWA) simulant is described. The analytical variability of methodologies currently used by Department of Defense testing laboratories was dramatically reduced by modifying the test cell and experimental procedures while maintaining compatibility with military testing specifications. Utilizing an on-line calibration system, cryogen-free preconcentrator, and flame ionization detector, the integrated system has demonstrated excellent repeatability, reproducibility, and high sampling frequency for a variety of non-porous and air-penetrable swatch samples challenged with methyl salicylate.

Activated Carbon Nonwoven as Chemical Protective Materials

The process of manufacturing an activated carbon nonwoven made by cotton fiber was investigated. The study was focused on cotton nonwoven formation, carbonization, activation, and characterization of the activated carbon nonwoven. Pyrolysis of the cotton carbonization was analyzed using TGA. There was a considerable decrease in weight loss in the region between 250°C to 400°C and the proper carbonized temperature was 400°C. The SEM examination indicated that the surface area of cotton fiber was increased significantly because the inside hollow of cotton fiber was widely opened and some small agglomerated particles were gasified after activation. Absorbability of the activated carbon nonwoven was evaluated using an instrument of inverse gas chromatography. Dispersive surface energy, specific free energy, and total surface energy all indicated this trend: Carbonized Cotton > Activated Cotton > Raw Cotton. The activated carbon nonwoven exhibited the potential for use as high adsorbent and absorbent materials. They are light weight and bulky, advantageous in protective clothing applications and other consumer and industrial applications.

Barrier properties of chlorobutyl nanoclay composites

AbstractElastomeric materials are used as barriers to protect workers against exposure to chemicals. The effectiveness of a polymer as a chemical protective material depends on the rate of permeation of chemicals through it. The permeation rate is dependent on the type and amount of fillers added into the polymer matrix. In this study, Chlorobutyl nanoclay composites were prepared by addition of organically modified and unmodified nanoclays at different filler loadings. The nanocomposites were swollen in three solvents of varying cohesive energy density until equilibrium and desorption experiments were carried out. The data obtained from desorption experiments was used to determine the diffusion coefficients. The concentration‐dependent diffusion coeffecient (D) was calculated at high and low concentration regions and it was found that D is one‐order less in lower concentration region than in the higher concentration range. The aspect ratio of the nanoclay fillers in the composite was calculated by assuming square and disc shapes and it was found to vary with the type of solvent and the used and filler loading. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3630–3637, 2006

Estimation of permeation rate of chemicals through elastometric materials

Elastometric materials are used as barriers to protect workers against exposure to chemicals. The effectiveness of a polymer as a chemical protective material therefore depends on the rate of the permeation of chemicals through it. The permeation rate depends on the solubility and the diffusion coefficient of chemicals in the materials. The diffusion coefficient itself is a strong function of concentration of the chemicals in the polymeric material. Permeation rates can be measured directly using a permeation cell or they can be calculated from the solubility and the diffusion coefficient data. Sorption/desorption experiments can be used to determine solubility and an expression for the diffusion coefficient in terms of concentration. Experiments were conducted for the sorption and desorption of ethyl acetate in three glove (one butyl and two neoprene materials) and two garment (neoprene and chlorinated polyethylene) materials. The data collected were used to estimate the steady-state permeation rates of ethyl acetate through the materials. The results of the experiments show that the solubility of ethyl acetate in butyl rubber is 0.795 g/cm3, and the steady-state permeation rate is 0.32 μg cm−2 s−1. The solubility of the chemical through the three neoprene materials is in the range of 2.25–5.31 g/cm3, and the steady-state permeation rates vary from 27 to 43 μg cm−2 s−1. The solubility of ethyl acetate in the chlorinated polyethylene is 7.14 g/cm3, and the steady-state permeation rate is 62.43 μg cm−2 s−1. The experimental method is very simple to use and it requires a small sample of the material (less than 1 cm2) and only a few milliliters of the chemical. Sorption/desorption experiments can also provide information on the amount of additives extracted from an elastomeric material during contact with a chemical. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1265–1272, 2001

Using immersion test data to screen chemical protective clothing.

A test to screen chemical protective materials in order to select potential candidates for further testing has been examined. The method involved determining the weight and volume changes in materials caused by immersion in the challenge chemical. Simple regression analysis showed that relatively short breakthrough times based on weight change and final thickness could be predicted with 90% confidence. Better results were obtained when discriminant analysis was used to classify breakthrough times greater than either 4 or 8 hr as a function of the weight change and final thickness. In 6% or less of the cases, actual breakthrough times were less than 4 or 8 hr when the predicted times were greater than these values. Discriminant analysis also was used to classify permeation rates as less than either 90 or 400 mg/m2-min based on weight change and initial thickness. In this case, actual permeation rates less than these were predicted to be greater in 4% and 7% of the cases, respectively.