Solution Blow Spinning of Polymeric Nano-Composite Fibers for Personal Protective Equipment
Summary
The primary goal of this study is to describe a protocol to prepare polymeric fiber mats with consistent morphology via solution blow spinning (SBS). We aim to use SBS to develop novel, tunable, flexible polymeric fiber nanocomposites for various applications, including protective materials, by incorporating nanoparticles in a polymer-elastomer matrix.
Abstract
Light-weight, protective armor systems typically consist of high modulus (>109 MPa) and high-strength polymeric fibers held in place with an elastic resin material (binder) to form a non-woven, unidirectional laminate. While significant efforts have focused on improving the mechanical properties of the high-strength fibers, little work has been undertaken to improve the properties of the binder materials. To improve the performance of these elastomeric polymer binders, a relatively new and simple fabrication process, known as solution blow spinning, was used. This technique is capable of producing sheets or webs of fibers with average diameters ranging from the nanoscale to the microscale. To achieve this, a solution blow spinning (SBS) apparatus has been designed and built in the laboratory to fabricate non-woven fiber mats from polymer elastomer solutions.
In this study, a commonly used binder material, a styrene-butadiene-styrene block-co-polymer dissolved in tetrahydrofuran, was used to produce nanocomposite fiber mats by adding metallic nanoparticles (NPs), such as iron oxide NPs, that were encapsulated with silicon oil and thus incorporated in the fibers formed via the SBS process. The protocol described in this work will discuss the effects of the various critical parameters involved in the SBS process, including the polymer molar mass, the selection of the thermodynamically appropriate solvent, the polymer concentration in solution, and the carrier gas pressure to assist others in performing similar experiments, as well as provide guidance to optimize the configuration of the experimental setup. The structural integrity and morphology of the resultant non-woven fiber mats were examined using scanning electron microscopy (SEM) and elemental X-ray analysis via energy-dispersive X-ray spectroscopy (EDS). The goal of this study is to evaluate the effects of the various experimental parameters and material selections to optimize the structure and morphology of the SBS fiber mats.
Introduction
Many light-weight, ballistic, protective armor systems are currently constructed using high-modulus and high-strength polymeric fibers, such as oriented, ultra-high molar mass polyethylene fibers or aramids, which provide outstanding ballistic resistance1,2. These fibers are used in combination with an elastic resin material (binder) that can penetrate to the filament level and secure the fibers in a 0°/90° configuration to form a non-woven, unidirectional laminate. The percentage of the polymer elastomer resin (binder) should not exceed 13% of the total weight of the unidirectional laminate to maintain the structural integrity and antiballistic properties of the laminate structure3,4. The binder is a very important component of the armor as it keeps the high-strength fibers properly oriented and tightly packed within each laminate layer3. Elastomer materials commonly used as binders in body armor applications have very low tensile modulus (e.g., ~17.2 MPa at ~23 °C), low glass transition temperature (preferably below -50 °C), very high elongation at break (as high as 300%) and must demonstrate excellent adhesive properties5.
To improve the performance of these polymer elastomers, SBS was performed to create fibrous elastomer materials that can be used as binders in body armor applications. SBS is a relatively new, versatile technique allowing the use of different polymer/solvent systems and the creation of different end products6,7,8,9,10,11,12,13. This simple process involves the rapid (10x the rate of electrospinning) deposition of conformal fibers onto both planar and nonplanar substrates to fabricate sheets or webs of fibers that encompass nano and micro length scales14,15,16,17,18. SBS materials have numerous applications in medical products, air filters, protective equipment, sensors, optical electronics, and catalysts14,19,20. Developing small diameter fibers can drastically increase the surface area to volume ratio, which is very important for several applications, especially in the personal protective equipment field. The diameter and morphology of the fibers generated by SBS depend on the molar mass of the polymer, polymer concentration in the solution, viscosity of the solution, polymer solution flow rate, gas pressure, working distance, and diameter of the spray nozzle14,15,17.
An important characteristic of the SBS apparatus is the spray nozzle consisting of an inner and a concentric outer nozzle. The polymer dissolved in a volatile solvent is pumped through the inner nozzle while a pressurized gas flows through the outer nozzle. The high-velocity gas exiting the outer nozzle induces shearing of the polymer solution flowing through the inner nozzle. This forces the solution to form a conical shape when exiting the spray nozzle. When the surface tension at the tip of the cone is overcome, a fine stream of polymer solution is ejected, and the solvent rapidly evaporates causing polymer strands to coalesce and deposit as polymer fibers. The formation of a fibrous structure, as solvent evaporates, strongly depends on the polymer molar mass and the solution concentration. Fibers are formed by chain entanglement, when polymer chains in solution begin to overlap at a concentration known as the critical overlap concentration (c*). Therefore, it is necessary to work with polymer solutions above the c* of the polymer/solvent system selected. Also, an easy strategy to attain this is to choose polymers with relatively high molar mass. Polymers with higher molar mass have increased polymer relaxation times, which is directly related to an increase in the formation of fibrous structures, as described in the literature21. As many of the parameters used in SBS are strongly correlated, the goal of this work is to provide guidance to develop tunable, and flexible polymeric fiber nanocomposites to be used as alternatives for typical binder materials found in body armor applications by incorporating nanoparticles in the fibrous polymer-elastomer matrix.
Protocol
Representative Results
Discussion
The method described herein provides a protocol for producing polymer elastomer nanocomposite fiber mats via a relatively new technique known as solution blow spinning. This technique allows the fabrication of fibers in the nanoscale and has several advantages over other well-established techniques, such as the electrospinning process, as it can be carried out under atmospheric pressure and room temperature27. Furthermore, SBS is not highly susceptible to local environmental changes (temperature o…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors would like to acknowledge Mr. Dwight D. Barry for his important contributions for fabrication of the solution blow spinning apparatus. Zois Tsinas and Ran Tao would like to acknowledge funding from the National Institute of Standards and Technology under Awards # 70NANB20H007 and # 70NANB15H112, respectively.
Materials
| 45 MM Toolmaker Vise | Tormach Inc. | 32547 | To secure substrate onto the collector |
| ARES-G2 Rheometer | TA Instruments | 401000.501 | Rheometer |
| Branson Ultrasonics M Series – Ultrasonic Cleaning Bath | Fisher Scientific | 15-336-100 | To disperse nanoparticles |
| Cadence Science Micro-Mate Interchangeable Syringe | Fisher Scientific | 14-825-2A | Glass Syringe 5mL in 1/5mL, Luer Lock Tip |
| Chemical hood | Any company | ||
| Corning – Disposable Pasteur Glass Pipette | Sigma Aldrich | CLS7095D5X-200EA | Non-Sterile |
| DWK Life Sciences Wheaton – Glass Scintillation Vial | Fisher Scientific | 03-341-25G | 20 mL with cap |
| FEI Quanta 200 Scanning Electron Microscope (SEM) | FEI | For imaging samples | |
| Iron Oxide Nanopowder/Nanoparticles | US Research Nanomaterials, inc. | US3320 | Fe3O4, 98%, 20-3- nm, Silicon oil Coated |
| KD Scientific Legato 100 Single-Syringe Pump | Sigma Aldrich | Z401358-1EA | Single syringe infusion pump |
| Master Airbrush – Model S68 | TCP Global | MAS S68 | Nozzle/needle diameter: 0.35 mm |
| Mettler Toledo AB265-S/FACT Scale | Cole-Parmer Scientific | EW-11333-14 | For weighing polymer and Nanoparticles |
| N2 Gas Regulator | Any company | ||
| Nanoenclosure | Any company | ||
| Optical Microscopy Glass Slides | Fisher Scientific | 12-550-A3 | Used as a substrate for fiber mat deposition |
| OSP Slotted Bob, 33 mm | TA Instruments | 402796.902 | Bob, upper geometry |
| OSP Slotted Double Gap Cup, 34 mm | TA Instruments | 402782.901 | Double wall cup, lower geometry |
| Oxford BenchMate Digital Vortex Mixer | Pipette | VM-D | Rated up to 4,200 rpm, for mixing solutions |
| Oxford Benchmate Tube Roller | Pipette | OTR-24DR | Sample mixer/rotator |
| Polystyrene-block-polybutadiene-block-polystyrene | Sigma Aldrich | 432490-1KG | styrene 30 wt. %, Mw ~ 185,000 g/mol |
| SEM Pin Stub Specimen Mount | Ted Pella Inc. | 16119 | 18 mm diameter x 8 mm height |
| Spatula | VWR | 82027-532 | To load test materials |
| Tetrahydrofuran (THF) | Fisher Scientific | T425-1 | solvent, HPLC grade |
| TRIOS | TA Instruments | v4.3.1.39215 | Rheometer software |
References
- Lee, B. L., et al. Penetration failure mechanisms of armor-grade fiber composites under impact. Journal of Composite Materials. 35 (18), 1605-1633 (2001).
- Prevorsek, D. C., Kwon, Y. D., Chin, H. B. Analysis of the temperature rise in the projectile and extended chain polyethylene fiber composite armor during ballistic impact and penetration. Polymer Engineering and Science. 34 (2), 141-152 (1994).
- Park, A. D., Park, D., No Park, A. J. . U.S. Patent. , (2006).
- No Park, A. D. . U.S. Patent. , (1995).
- Harpell, G. A., Prevorsek, D. C., Li, H. L. Flexible multi-layered armor. Patent No. WO/1989. , (1989).
- Cena, C., et al. BSCCO superconductor micro/nanofibers produced by solution blow-spinning technique. Ceramics International. 43 (10), 7663-7667 (2017).
- Miller, C. L., Stafford, G., Sigmon, N., Gilmore, J. A. Conductive nonwoven carbon nanotube-PLA composite nanofibers towards wound sensors via solution blow spinning. IEEE Transactions on Nanobioscience. 18 (2), 244-247 (2019).
- Iorio, M., et al. Conformational changes on PMMA induced by the presence of TiO 2 nanoparticles and the processing by Solution Blow Spinning. Colloid and Polymer Science. 296 (3), 461-469 (2018).
- Martínez-Sanz, M., et al. Antimicrobial poly (lactic acid)-based nanofibres developed by solution blow spinning. Journal of Nanoscience and Nanotechnology. 15 (1), 616-627 (2015).
- Wang, H., et al. Highly flexible indium tin oxide nanofiber transparent electrodes by blow spinning. ACS Applied Materials and Interfaces. 8 (48), 32661-32666 (2016).
- Greenhalgh, R. D., et al. Hybrid sol-gel inorganic/gelatin porous fibres via solution blow spinning. Journal of Materials Science. 52 (15), 9066-9081 (2017).
- Gonzalez-Abrego, M., et al. Mesoporous titania nanofibers by solution blow spinning. Journal of Sol-Gel Science and Technology. 81 (2), 468-474 (2017).
- Oliveira, J. E., Zucolotto, V., Mattoso, L. H., Medeiros, E. S. Multi-walled carbon nanotubes and poly (lactic acid) nanocomposite fibrous membranes prepared by solution blow spinning. Journal of Nanoscience and Nanotechnology. 12 (3), 2733-2741 (2012).
- Medeiros, E. S., Glenn, G. M., Klamczynski, A. P., Orts, W. J., Mattoso, L. H. Solution blow spinning: A new method to produce micro-and nanofibers from polymer solutions. Journal of Applied Polymer Science. 113 (4), 2322-2330 (2009).
- Vasireddi, R., et al. Solution blow spinning of polymer/nanocomposite micro-/nanofibers with tunable diameters and morphologies using a gas dynamic virtual nozzle. Scientific Reports. 9 (1), 1-10 (2019).
- Tutak, W., et al. The support of bone marrow stromal cell differentiation by airbrushed nanofiber scaffolds. Biomaterials. 34 (10), 2389-2398 (2013).
- Daristotle, J. L., Behrens, A. M., Sandler, A. D., Kofinas, P. A review of the fundamental principles and applications of solution blow spinning. ACS Applied Materials and Interfaces. 8 (51), 34951-34963 (2016).
- Hofmann, E., et al. Microfluidic nozzle device for ultrafine fiber solution blow spinning with precise diameter control. Lab on a Chip. 18 (15), 2225-2234 (2018).
- Behrens, A. M., et al. In situ deposition of PLGA nanofibers via solution blow spinning. ACS Macro Letters. 3 (3), 249-254 (2014).
- Vural, M., Behrens, A. M., Ayyub, O. B., Ayoub, J. J., Kofinas, P. Sprayable elastic conductors based on block copolymer silver nanoparticle composites. ACS Nano. 9 (1), 336-344 (2015).
- Srinivasan, S., Chhatre, S. S., Mabry, J. M., Cohen, R. E., McKinley, G. H. Solution spraying of poly (methyl methacrylate) blends to fabricate microtextured, superoleophobic surfaces. Polymer. 52 (14), 3209-3218 (2011).
- Flory, P. J. . Principles of polymer chemistry. , (1953).
- Palangetic, L., et al. Dispersity and spinnability: Why highly polydisperse polymer solutions are desirable for electrospinning. Polymer. 55 (19), 4920-4931 (2014).
- Ying, Q., Chu, B. Overlap concentration of macromolecules in solution. Macromolecules. 20 (2), 362-366 (1987).
- Haro-Pérez, C., Andablo-Reyes, E., Díaz-Leyva, P., Arauz-Lara, J. L. Microrheology of viscoelastic fluids containing light-scattering inclusions. Physical Review E. 75 (4), 041505 (2007).
- Thiele, J., et al. Early development drug formulation on a chip: Fabrication of nanoparticles using a microfluidic spray dryer. Lab on a Chip. 11 (14), 2362-2368 (2011).
- Zhao, J., Xiong, W., Yu, N., Yang, X. Continuous jetting of alginate microfiber in atmosphere based on a microfluidic chip. Micromachines. 8 (1), 8 (2017).
- Jun, Y., Kang, E., Chae, S., Lee, S. H. Microfluidic spinning of micro-and nano-scale fibers for tissue engineering. Lab on a Chip. 14 (13), 2145-2160 (2014).
- Weng, B., Xu, F., Salinas, A., Lozano, K. Mass production of carbon nanotube reinforced poly (methyl methacrylate) nonwoven nanofiber mats. Carbon. 75, 217-226 (2014).
- Barton, A. F. Solubility parameters. Chemical Reviews. 75 (6), 731-753 (1975).
