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Durable Stretch Barrier Materials

Description:

TECHNOLOGY AREA(S): Chem Bio_defense, Materials 

OBJECTIVE: Commercially available Chemical, Biological, Radioactive, and Nuclear (CBRN) protective ensembles are bulky and with a high thermal burden due to the lack of stretch of the materials used. The bulk of the garment prevents agile movements of arms and legs needed while performing critical tasks. Materials with stretch enable a more conformable garment to be designed, enabling ease of movement and better comfort for the wearer. This topic addresses the technical challenges and innovative solutions needed to create durable, stretch materials with barrier capabilities that can be integrated into novel CBRN protective ensembles. 

DESCRIPTION: Chemical, Biological, Radioactive, and Nuclear (CBRN) protective ensembles provide the first line of defense for personnel exposed to victims and/or materials during assessment, extrication, rescue, triage, decontamination, treatment, site security, crowd management, and force protection operations at incidents involving CBRN terrorism agents. Current protective ensembles are designed to meet National Fire Protection Association (NFPA) 1994 Class 1 protection standards [1]. Commercially available CBRN protective ensembles are bulky and not sufficiently conformal or tactile to the wearer. It is well known that a simple body movement may extend the body skin by 50% or more and the fabric must be able to accompany the stretch and recover on relaxation. Elastic fabrics are an important route to achieve comfort, tactility and freedom of movement of the body with a conformal fit [2]. Elastic garments used in athletics and sports are assumed to improve athlete’s performance in cycling, swimming, and so on. This type of fabric enables freedom of body movement by reducing the fabric resistance to body stretch. Elastic fibers and fabrics under trade names such as Lycra and Spandex are widely used in many areas where elasticity is needed such as tights, sportswear, swimwear, wet suits, SCUBA dive skins, etc. Stretch fabric materials are also of interest in wearable electronics [3] and tactile sensing applications [4]. It would be highly beneficial if performance can be extended by the CBRN protective material by adding stretch to provide agility and comfort to the wearer with a more conformable garment design. The challenge is the development of novel stretch materials that could also deliver the stringent protection function and durability. It is also recognized that repetitive biaxial stretching could affect the functional properties of the stretch materials and any material design should account for this challenge as well [5]. This topic solicits the following innovative technology requirements: a) The stretch barrier material should satisfy the threshold barrier properties against vapor and liquid challenges with appropriate simulants selected for the study, with standard test protocols specified above. b) The basic mechanical properties to be evaluated include the stress-strain behavior under biaxial stretching and the extent of reversibility of stretching. Materials that can be stretched isotropically with 12% or more along each linear dimension are preferred, recognizing that 12% is the threshold and 20% is the preferred objective. Stretch properties should be tested per ASTM D2594 in both linear dimensions as well as on the bias. c) The material should possess durability in barrier function after being subjected to flexing, abrasion and cycles of biaxial stretching and relaxation. This should be demonstrated by testing for the barrier properties after subjecting the stretch material to the different stressors defined above. d) Since the stretch material forms a part of the protective ensemble and is not expected to provide all needed functionalities such as fire or flame resistance (FR), it will be combined with other materials eventually to create final product of interest. Keeping that in view, the stretch materials should be designed so that it would be possible to bond/integrate the material with FR fabrics like Nomex, for example. Similarly, the potential for the material to manufacture garments should be demonstrated by overcoming problem areas such as seams. The barrier materials should offer protection against vapor and liquid chemical agent challenges tested using American Society for Testing and Materials (ASTM) F739. 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 as above but when challenged with 100 g/m2 of liquid chemical agent or 100% agent in gas phase. Also, the permeation is to be tested after subjecting the material to 100 cycles of flexing per ASTM F392 and 25 cycles of abrasion with 80 grit paper per ASTM D4157. 

PHASE I: Conduct research on novel concepts for stretch barrier materials to achieve both stretch and barrier functions. Upon completion of Phase I, samples of the stretch material should be made available for independent evaluation of stretch and barrier properties. The system should meet the threshold goal of 12% linear strain that is reversible and barrier properties at the threshold level against selected chemical simulants based on liquid and vapor challenges. The barrier testing for Phase I can be limited to the ‘as-produced’ stretchable material. Tests for durability in barrier properties after subjecting the stretch barrier material to stresses like flexing, abrasion or repetitive biaxial stretching are not required for Phase I. The detailed conditions for testing must be approved by the Government Technical POC. 

PHASE II: Further improvements in stretch should be made to reach as high a value as possible near the objective of 20% reversible strain level. The barrier properties should meet the threshold level for both liquid and vapor challenges for selected chemical agent simulants, and improvements in barrier performance towards the objective should be demonstrated. The testing should be conducted after subjecting the stretch barrier material to flexing, abrasion and repetitive biaxial stretching. The detailed conditions for testing must be approved by the Government Technical POC. Methods must be developed to bond/integrate the stretch barrier material with other functional materials such as Nomex FR fabric, identified by the Government Technical POC. At the conclusion of Phase II, swatches of stretch barrier fabric samples obtained from continuous pilot scale production should be made available for independent evaluation. PHASE III: The stretch barrier material successfully demonstrated in Phase II will be integrated into CBRN protective ensemble. Materials should be made in full width production and issues in garment manufacture that may arise, such as seams, will be addressed. 

PHASE III: PHASE III: The stretch barrier material successfully demonstrated in Phase II will be integrated into CBRN protective ensemble. Materials should be made in full width production and issues in garment manufacture that may arise, such as seams, will be addressed. PHASE III DUAL USE APPLICATIONS: First responder and anti-terrorism personnel would also benefit from the use of improved protective garments that are more conformal and stretchable, allowing for improved agility and comfort. The stretch fabric can be used not only in protective clothing, but also in other applications such as respirator face seals, face masks in hospitals, schools, and other buildings when high levels of protection are desired. 

REFERENCES: 

1: 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:  M. Senthilkumar, N. Anbumani and J. Hayavadana, Elastane fabrics – A tool for stretch applications in sports, Indian J. Fiber and Textiles Research 36 (2011) 300-307.

3:  C. Wang, M. Zhang, K. Xia, X. Gong, H. Wang, Z. Yin, B. Guan and Y. Zhang, Intrinsically Stretchable and Conductive Textile by a Scalable Process for Elastic Wearable Electronics, ACS Appl. Mater. Interfaces 9 (2017) 13331−13338.

4:  G. H. Büscher, R. Kõiva, C. Schürmann, R. Haschke, and H. J. Ritter, Flexible and stretchable fabric-based tactile sensor, Robotics and Autonomous Systems 63 (2015) 244–252.

5:  H. S. Kim and C. H. Park, Effect of biaxial tensile extension on superhydrophobicity of rayon knitted fabrics, RSC Adv. 6 (2016) 48155.

KEYWORDS: Stretch Fabrics, Barrier Materials, Chem-bio Protection, Biaxial Stress-strain, Durability, Permeation Resistance, Elastic Stretching; Elastic Relaxation 

CONTACT(S): 

Ramanathan Nagarajan 

(508) 233-6445 

ramanathan.nagarajan.civ@mail.mil 

Molly Richards 

(508) 233-4310 

Natalie Pomerantz 

(508) 233-4047 

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