RT&L FOCUS AREA(S): Warfighting Requirements (GWR) TECHNOLOGY AREA(S): Chemical/Bio Defense, Materials/Processes OBJECTIVE: Design and develop a non-PFAS elastomeric barrier that provides permeation resistance to CBRN agents. DESCRIPTION: The primary requirements for Chemical, Biological, Radioactive, and Nuclear (CBRN) protective items such as garments, gloves, boots, and masks are that they (i) ensure barrier function against various chemical challenges, (ii) provide flexibility and stretch for ease of movement and comfort for the wearer, (iii) possess adequate mechanical strength as required for the application, and (iv) do not compromise the barrier and mechanical properties when subjected to environmental and operational stressors. Desired properties for protective items are described in the National Fire Protection Association (NFPA) 1994 Class 1 standard [1]. Typical CBRN elastomer materials are either thermally cross-linked compounds or melt-processed thermoplastic polymers. Cross-linked materials are generally less susceptible to chemical permeation due a more restricted swelling in these systems. Often, a reinforcing filler (i.e., carbon black) is incorporated for mechanical property enhancement. While the increased filler content will reduce permeation, it also causes increased system stiffness and hardness. No commercially available elastomer can provide the range of resistance required to protect from the entire range of potential chemical challenges including chemical warfare agents (CWAs), toxic industrial chemicals (TICs), fuels, lubricants, solvents, vapors, and acids and bases, while retaining sufficient stretch. Fluoropolymers or copolymers or coatings involving them have been added to elastomeric materials in order to impart or enhance barrier properties. The unique combination of properties of fluorine-containing polymers such as excellent chemical resistance, permittivity, flame resistance, hydro- and oleophobicity, weak adhesion and low cohesion have led to their applicability as membrane constituents or as coatings or fillers in chemical barrier materials. However, environmental concerns are beginning to require the reduced use and eventual elimination of fluorine containing systems [2, 3] and have stimulated the search for alternatives [4]. This topic calls for the design of novel, non-PFAS* elastomeric barrier systems that can provide improved permeation resistance. Approaches include but are not limited to: tailoring polymers using known approaches such as multilayers, interpenetrating polymers, coatings, or fillers; and rational design of novel polymer molecular structures [5]. The barrier materials should offer protection against vapor and liquid TICs and chemical agent challenges. The threshold level of permeation resistance should be cumulative permeation mass of less than 6 micrograms/cm2 for industrial chemicals, 1.25 micrograms/cm2 for Soman and 4.0 micrograms/cm2 for distilled mustard when challenged with 20 grams per meter squared (g/m2) of liquid chemical agent or 1% agent in gas phase. The permeation is to be tested after subjecting the material to 100 cycles of flexing per ASTM F392 and 10 cycles of abrasion with 600 grit paper as per ASTM D4157. The objective level of permeation is the same cumulative permeation mass limits assessed after 6 hours. Testing permeation resistance can be performed with appropriate simulants using standard test protocols specified in the reference document [1]. The detailed conditions for testing must be approved by the Government Technical POC. *For the purposes of this SBIR topic, non-PFAS items are defined as those not containing fluorine. Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. PHASE I: Demonstrate a fluorine-free elastomeric barrier material that demonstrates the required barrier properties for one industrial chemical (e.g. tetrachloroethylene) and one chemical weapons agent (CWA) simulant (e.g dimethyl methylphosphonate) while retaining the desired physical properties: flame resistance as defined by ASTM F1358 (after flame time less than or equal to ( ) 2 sec); system should meet the threshold goal of 12% linear strain that is reversible. It is expected that at least one novel barrier candidate is produced in a 3 x 3 swatch for repellency studies. Outline a potential scale-up method and cost assessment for the material. PHASE II: Optimize, scale and formulate minimally one candidate material for chemical repellency testing against a chemical agent** (e.g. Soman) and additional industrial chemicals (dimethyl sulfate and toluene). Provide a 6 x 6 swatch for independent agent evaluation by the end of Phase II/Month 10. In addition to assessing the physical properties noted in Phase I (flame resistance, reversible linear strain), determine puncture resistance as defined by ASTM 1342/F1342M Method A (puncture force 36 N). Methods must be developed to bond/integrate the elastomeric barrier material with other functional materials such as Nomex FR fabric, as identified by the Government Technical POC. At the conclusion of Phase II, elastomeric barrier fabric sample, at least 12 inches wide and 5 yards in length, obtained from continuous pilot scale production should be made available for independent evaluation. ** Use of any chemical agent will require the small business to work with an approved chemical surety laboratory PHASE III: The elastomeric barrier material successfully demonstrated in Phase II will be integrated into CBRN protective ensemble. Materials should be made in full width (40") production, and issues in garment manufacture that may arise, such as seams, will be addressed. PHASE III DUAL USE APPLICATIONS: An improved elastomeric, chemical barrier material would have a broad range of dual use applications with first responders, anti-terrorism personnel, agrochemical (pesticide) applications personnel and industrial, medical, and laboratory personnel. REFERENCES: 1. a) NFPA 1990 Standard on Protective Ensembles for Chemical/Biological Terrorism Incidents 2022 Edition, National Fire Protection Association (NFPA), Quincy, MA 02269, USA. https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=1990 . Note that the 2022 Edition of NFPA 1990 is a combination of Standards NFPA 1991, NFPA 1992, and 1994. b) NFPA 1994 Standard on Protective Ensembles for Chemical/Biological Terrorism Incidents 2001 Edition, National Fire Protection Association (NFPA), Quincy, MA 02269, USA. http://www.disaster-info.net/lideres/english/jamaica/bibliography/ChemicalAccidents/NFPA_1994_StandardonProtectiveEnsemblesforChemicalBiologicalTerrorismIncidents.pdf 2. National Defense Authorization Act for Fiscal Year 2022 https://www.congress.gov/bill/117th-congress/senate-bill/1605/text 3. R. Lohmann, I. T. Cousins, J. C. DeWitt, J. Gl ge, G. Goldenman, D. Herzke, A. B. Lindstrom, M. F. Miller, C. A. Ng, S. Patton, M. Scheringer, X. Trier, and Z. Wang, Are Fluoropolymers Really of Low Concern for Human and Environmental Health and Separate from Other PFAS? Environ. Sci. Technol. 54 (2020) 12820 12828. 4. G. Glenn, R. Shogren, X. Jin, W. Orts, W. Hart-Cooper, and L. Olson, Per- and polyfluoroalkyl substances and their alternatives in paper food packaging, Compr. Rev. Food Sci. Food Saf. 20 (2021) 2596 2625. 5. M A R. Bhuiyan, L. Wang, A. Shaid, R. A Shanks and J. Ding, Advances and applications of chemical protective clothing system, J. Industrial Textiles 49 (2019) 97-138. KEYWORDS: chem-bio protection, PFAS, fluorine-free, permeation resistance, elastomer
