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Aerogels for Space Applications
Aerogels are excellent thermal insulators, have unique pore structures, and can be engineered into various net-shapes to suit particular applications. Our research involves the production of net-shape aerogel articles from both polymeric substrates and silica. Silica aerogels are more challenging as they do not offer the desired mechanical integrity. Efforts to crosslink networks of silica aerogels by epoxies and polyurethanes have resulted in some success at NASA and other research laboratories, but the compressive strengths of these materials are still poor. We have developed methods by which networks of aerogels can be crosslinked using silane-modified polyurethanes, organic-inorganic hybrid nanoparticles, and self-crosslinking multifunctional silanes to improve the compressive strength. The research program has led to the development of a low-density shape memory aerogel composite material for potential applications in space suits and space shuttles. Our study investigated structure-property relationships, manufacturing methods, and crosslinking chemistry.
References
Randall, Jason P., Mary Ann B. Meador, and Sadhan C. Jana. "Tailoring mechanical properties of aerogels for aerospace applications." ACS applied materials & interfaces 3.3 (2011): 613-626.
Aerogels for Net-Shape Manufacturing
We have also worked on net-shape manufacturing of aerogel articles from silica and polymers. This project aimed to eliminate the need for batch-type, slow solvent-exchange step by directly subjecting the aerogel sleeves to continuous solvent exchange.
References
Chaotic Mixers as Chemical Reactors
Chemical conversion in diffusion-limited reactive systems is seen to increase dramatically with the application of chaotic mixing. The time scale of chemical conversion is much shorter when ingredients are mixed in a chaotic mixer reactor. The uniformity of chaotic mixing provides narrow block length distribution in A2+B2+C2 type polymerization schemes, such as polyurethanes, and creates fine-scale morphology in polymeric systems with reaction-induced phase separation.
The performance of chaotic mixers is analyzed in terms of the effects of mixer designs and mixer operating conditions on polymer molecular weight and properties. Specifically, the analysis involves the computation of time scales of mixing and chemical reactions and finding their relationship to mixing torque, polymer molecular weight, and mechanical and thermal properties. It is found that the time scale of mixing has a strong dependence on the Liapunov exponent, a parameter used to characterize the degree of chaotic mixing. The results show that the highest polymer molecular weight is obtained when the mixer operates under globally chaotic conditions and when the magnitudes of the time scales of mixing and chemical reactions are made comparable to each other. The study also shows that hard segment phase separation can reduce the value of the reaction rate constant and hence hinder the progress of polymerization.
References
Jana, S.C., Jung, C.D., 2007 Synthesis of thermoplastic polyurethanes of aliphatic diisocyanates under chaotic mixing conditions. Submitted to Chem. Eng. Sci.
Jung, C.D., Gunes, I.S., Jana, S.C., 2007 Time scales of mixing and chemical reactions in synthesis of thermoplastic polyurethanes in chaotic mixers. Ind. Eng. Chem. Res., 46, 2413-2422.
Jung, C.D., Jana, S.C. 2005 Effect of chaotic mixing on catalyzed thermoplastic polyurethane polymerization. SPE ANTEC 63, 1800-1804.
Jung, C.D., Jana, S.C., 2004 Synthesis of thermoplastic polyurethanes by chaotic mixing. SPE ANTEC 62, 2814-2818.
Chaotic Mixing to Disperse Nanofillers
Our study demonstrates that nanofillers such as layered silicate clay, carbon nanofibers, and silicon carbide disperse effectively in polymeric matrices when mixed using chaotic mixers. This method enhances the alignment of layered silicate clay and carbon nanofibers along the flow direction and minimizes damage to high aspect ratio nanofillers. For instance, electrically conductive composites of poly(methyl methacrylate) with carbon nanofibers exhibit a lower percolation threshold (approximately 2 wt.% CNF) compared to those prepared in internal mixers. The chaotic mixing process effectively disperses and orients nanofibers to form conductive networks, as observed with treated carbon nanofibers and polyurethanes.
Chaotic mixing-induced orientation of layered silicate clay in bisphenol A polycarbonate (unpublished)
Chaotic mixing-induced orientation of carbon nanofibers in polymethylmethacrylate (Composites Part A: Appl. Sci. Manu., 38, 983-993.)
Volume electrical conductivity of PMMA/CNF composites. Results from materials mixed in chaotic mixer and Brabender Plasticorder are identified. (Composites Part A: Appl. Sci. Manu., 38, 983-993.)
References
1. Jimenez, G., Jana, S.C. (2007). Polymer composites of oxidized carbon nanofibers prepared by chaotic mixing. *Carbon*, 45(10), 2079-2091.
2. Jimenez, G., Jana, S.C. (2007). Electrically conductive polymer nanocomposites of polymethylmethacrylate and carbon nanofibers prepared by chaotic mixing. *Composites Part A: Appl. Sci. Manu.*, 38, 983-993.
3. Jimenez, G., Jana, S.C. (2007). Polyurethane-carbon nanofiber composites for shape memory effects. *SPE ANTEC*, 65, 18-22.
4. Jimenez, G., Jana, S.C. (2006). Polymer composites of modified carbon nanofibers prepared by chaotic mixing. *SPE ANTEC*, 64, 352-356.
5. Jimenez, G., Jana, S.C. (2005). Preparation of poly(methylemethacrylate) and carbon nanofiber composites by chaotic mixing. *SPE ANTEC*, 63, 1938-1942.
Novel Polymer Nanocomposites
We have developed new materials for structural, electronic, electrical, and shape memory applications by combining nanoscopic metallic, semi-conducting, and non-metallic inorganic particles with high-performance engineering thermoplastics, thermoplastic elastomers, and thermosetting polymers. The focus of this research was to develop a fundamental understanding of nanofiller dispersion in thermosets (epoxies and PMR polyimides), polyolefins, thermoplastic polyurethane elastomers and foams, shape memory polymers, and polymer blends. Our study revealed that low molecular weight thermosetting resins could be used as dispersing agents of nanoparticulate fillers, such as fumed silica and layered silicates in thermoplastic polymers, such as polyether sulphone, polyphenylene ether, polyphenylene sulfide, etc.
(a) Epoxies | We also found that in epoxy-nanoclay systems, the ratio, G′/η, plays an important role in determining whether exfoliation, partial exfoliation, and intercalation occurs; G′ is the storage modulus of intra-gallery epoxy and |η*| is the complex viscosity of extra-gallery epoxy at an instant of time. Complete exfoliation is obtained for values of G′/| *| greater than ~4 1/s. Similar observations were made in the case of thermoset polyimides.
(b) PMR resins | We developed a novel method of nanoclay exfoliation in synthesis of nanocomposites of PMR-type thermoset resins. The method involves nanoclay intercalation by lower molecular weight PMR monomer prior to dispersion in primary, higher molecular weight PMR resin and resin curing to obtain the final composites. It was found that sonication of clay at the time of intercalation by lower molecular weight PMR resin helps achieve higher degree of exfoliation. In addition, clays obtained from ion exchange with a 50:50 mixture of N [4(4aminobenzyl)phenyl]-5 norborene-2,3-dicarboximide (APND), and dodecylamine (C12) showed better exfoliation than Cloisite® 30B clay and resultant nanocomposites show higher thermal stability and higher tensile modulus.
(c) TPU | Our group has developed a bulk polymerization method for efficient exfoliation of reactive layered silicate nanoparticles in thermoplastic polyurethane nanocomposites. The resultant materials with 3 wt% clay content offer more than 100% increase in tensile modulus and strength and almost no decrease in tensile elongation. Only micro-composites are produced in the case of non-reactive clays. It was also found that a balance between shear and extent of chemical reactions must be maintained to obtain best results – excessive clay-polymer reactions and low shear stress in polymerization results in micro-composites.
(d) Polyolefins | We investigated the nature of interactions between the molecules of polyhedral oligomeric silsesquioxane (POSS) containing silanol functionalities (silanol-POSS) and di(benzylidene)sorbitol (DBS) encountered in the development of nanocomposite fibers from the compounds of POSS, DBS, and isotactic polypropylene (iPP). The synergistic interactions were investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and oscillatory shear rheology. Mass and NMR spectrometry revealed that the molecules of silanol-POSS and DBS formed several amorphous non-covalent molecular complexes promoted by hydrogen bonding. More abundant complex formation was observed with silanol-POSS molecules carrying four silanol groups and phenyl substitutions. Such complex formation deterred fibrillation of DBS when the compounds of iPP, DBS, and silanol-POSS were cooled from the homogeneous melt states. It was also revealed that POSS-DBS complexes were of much lower viscosity than iPP, which resulted in significant reduction of viscosity of compounds of iPP, DBS, and silanol-POSS.
References
Roy, S., Lee, B.J., Kakish, Z.M., Jana, S.C. (2012). Exploiting sorbitol-POSS interactions: Issues of reinforcement of isotactic polypropylene spun fibers. Macromolecules, 45(5), 2420-2433.
Roy, S., Feng, J., Scionti, V., Jana, S.C., Wesdemiotis, C. (2012). Self-assembled structure formation from interactions between polyhedral oligomeric silsesquioxane and sorbitol in preparation of polymer compounds. Polymer, 53, 1711-1724.
Roy, S., Scionti, V., Jana, S.C.*, Wesdemiotis, C., Pischera, A.M., Espe, M.P. (2011). Sorbitol–POSS interactions on development of isotactic polypropylene composites. Macromolecules, 44, 8064–8079.
Gunes, I.S., Pérez-Bolívar, C., Jimenez, G.A., Celikbicak, O., Li, F., Anzenbacher, P., Wesdemiotis, C., Jana, S.C.* (2011). Analysis of energy transfer and ternary non-covalent filler/matrix/UV stabilizer interactions in carbon nanofiber and oxidized carbon nanofiber filled poly(methyl methacrylate) composites. Polymer, 52, 5355-5361.
Perilla, J.E., Lee, B.J., Jana, S.C*. (2010). Rheological investigation of interactions between sorbitol and polyhedral oligomeric silsesquioxane in development of nanocomposites of isotactic polypropylene. J. Rheol., 54(4), 761-779.
Gunes, I.S., Perez-Bolivar, C.A., Cao, F., Jimenez, G.A., Anzenbacher, P., Jana, S.C.* (2010). Analysis of non-covalent interactions between the nanoparticulate fillers and the matrix polymer as applied to shape memory performance. J. Mater. Chem., 20, 3467-3474.
Jimenez, G., Jana, S.C. (2009). Composites of carbon nanofibers and thermoplastic polyurethanes with shape memory properties prepared by chaotic mixing. Polym. Eng. Sci., 49(10), 2020-2030.
Ertekin, A., Jana, S.C., Thomas, R. (2009). An investigation on the capillary wetting of glass fiber tow and fabric structures with nanoclay-enriched reactive epoxy and silicone oil mixtures. ACS Appl. Mater. Interfaces, 1(8), 1662-1671.
Gunes, I.S., Jimenez, G., Jana, S.C. (2009). Carbonaceous fillers for shape memory actuation of polyurethane composites by resistive heating. Carbon, 47, 981-997.
Gunes, I.S., Cao, F., Jimenez, G., Jana, S.C. (2008). Evaluation of nanoparticulate fillers for development of shape memory polymer nanocomposites. Polymer, 49, 2223-2234.
Gunes, S., Jana, S.C. (2008). Shape memory polymers and their nanocomposites: A review of science and technology of new multifunctional materials. J. Nanosci. Nanotech., 8, 1616-1637.
Gintert, M., Jana, S.C., Miller, S. (2007). On optimum organic treatment of nanoclay for PMR-15 nanocomposites. Polymer, 48, 7573-7581.
Gintert, M., Jana, S.C., Miller, S. (2007). A novel strategy for nanoclay exfoliation in thermoset polyimide nanocomposite systems. Polymer, 48, 4166-4173.
Jimenez, G., Jana, S.C. (2007). Polymer composites of oxidized carbon nanofibers prepared by chaotic mixing. Carbon, 45(10), 2079-2091.
Jimenez, G., Jana, S.C. (2007). Electrically conductive polymer nanocomposites of polymethylmethacrylate and carbon nanofibers prepared by chaotic mixing. Composites Part A: Appl. Sci. Manu., 38, 983-993.
Cao, F., Jana, S.C. (2007). Nanoclay-tethered shape memory polyurethane nanocomposites. Polymer, 48(13), 3790-3800.
Dharaiya, D., Jana, S.C. (2005). Thermal decomposition of alkyl ammonium ions and its effects on surface polarity of organically treated nanoclay. Polymer, 46(23), 10139-10147.
Dharaiya, D., Jana, S.C. (2005). Nanoclay-induced morphology development in chaotic mixing of immiscible polymers. J. Polym. Sci., Part B: Physics, 43(24), 3638-3651.
Pattanayak, A., Jana, S.C. (2005). Thermoplastic polyurethane nanocomposites of reactive silicate clays: Effects of soft segments on properties. Polymer, 46(14), 5183-5193.
Pattanayak, A., Jana, S.C. (2005). High strength and low stiffness composites of nanoclay-filled thermoplastic polyurethanes. Polym. Eng. Sci., 45(11), 1532-1539.
Pattanayak, A., Jana, S.C. (2005). Properties of bulk-polymerized thermoplastic polyurethane nanocomposites. Polymer, 46(10), 3394-3406.
Pattanayak, A., Jana, S.C. (2005). Synthesis of thermoplastic polyurethane nanocomposites of reactive clay by bulk polymerization methods. Polymer, 46(10), 3275-3288.
Park, J.H., Jana, S.C. (2004). Adverse effects of thermal dissociation of quaternary ammonium ions on nanoclay exfoliation in epoxy-clay systems. Polymer, 45(22), 7673-7679.
Park, J.H., Jana, S.C. (2003). A case study on the effects of plasticization of epoxy networks by organic treatment on exfoliation of nanoclay. Macromolecules, 36, 8391-8397.
Park, J.H., Jana, S.C. (2003). Mechanism of exfoliation of nanoclay particles in epoxy-clay nanocomposites. Macromolecules, 36(8), 2758-2768.
Park, J.H., Jana, S.C. (2003). The relationship between nano- and micro-structures and mechanical properties in PMMA-epoxy-nanoclay composites. Polymer, 44(7), 2091-2100.
Jana, S.C., Jain, S. (2001). Dispersion of nanofillers in high performance polymers using reactive solvents as processing aids. Polymer, 42(16), 6897-6905.
Tire Tread with Low-Rolling Resistance via Improved Mixed Filler Dispersion
Formulators often encounter two conflicting scenarios when developing tire tread compounds. Initially, fillers must be dispersed to the scale of a few hundred nanometers to maximize the window of mechanical reinforcement. However, product developers sometimes accept a coarser dispersion scale, e.g., a mean particle size of around a micrometer. At this scale, the particles serve as defects. Additionally, the tread experiences periodic agglomeration and breakup of particle networks due to large strains, although the overall compound performance remains satisfactory. This process leads to what is known as hysteresis, which is the main cause behind high-rolling resistance. One may then argue that minimizing particle networking would reduce the hysteresis loss. Yet, a certain level of particle networking is necessary for the mechanical stiffness of the compound. Our work explores these scenarios with carbon back and silica-filled rubber compounds.
Achieving fine-scale dispersion of silica and carbon black (CB) particles in tire tread compounds enhances mechanical toughness and wet-track resistance. The polar nature of silica surfaces requires treatment with silane-type coupling agents, while carbon black particles can be well-dispersed without specific coupling agents. A higher rolling resistance is attributed to hysteresis loss, which in turn is governed by particle network breakdown and agglomeration during high-strain deformation. Our approach includes subduing particle network breakdown by encasing the particles with sustainable materials such as lignin or using novel polymeric coupling agents. For the former, results show significant promise for reduction of loss tangent at 60 °C by 10-20% while maintaining the loss tangent at 0 °C. Furthermore, we introduced novel polymeric coupling agents to promote the dispersion of carbon black and silica via two entirely different routes – the former via arene-perfluoroarene interactions and the latter via the formation of Si-O-Si linkages. The tensile and viscoelastic properties are analyzed as a function of dispersion quality and the molecular architecture of the novel coupling agents.
References
Pugh, C., Jana, S. C., Swanson, N., Prasad, R., & Albehaijan, H. (2019). Polybutadiene graft copolymers as coupling agents for carbon black and silica dispersion in rubber compounds. U.S. Patent No. 10,472,449. Washington, DC: U.S. Patent and Trademark Office.
Kulkarni, A., Pugh, C., Jana, S. C., Wims, D. T., & Gawad, A. A. (2019). Crosslinking of SBR compounds for tire tread using benzocyclobutene chemistry. Rubber Chemistry and Technology, 92(1), 25-42.
Raut, P., Swanson, N., Kulkarni, A., Pugh, C., & Jana, S. C. (2018). Exploiting arene-perfluoroarene interactions for dispersion of carbon black in rubber compounds. Polymer, 148, 247-258.
Bahl, K., Swanson, N., Pugh, C., & Jana, S. C. (2014). Polybutadiene-g-polypentafluorostyrene as a coupling agent for lignin-filled rubber compounds. Polymer, 55(26), 6754-6763.
Bahl, K., Miyoshi, T., & Jana, S. C. (2014). Hybrid fillers of lignin and carbon black for lowering of viscoelastic loss in rubber compounds. Polymer, 55(16), 3825-3835.
Bahl, K., & Jana, S. C. (2014). Surface modification of lignosulfonates for reinforcement of styrene–butadiene rubber compounds. Journal of Applied Polymer Science, 131(7).
Processing of Self-Assembled Bottom-Up Polymer Nanocomposite Materials
2008-2012
Our collaborator was David A. Schiraldi at Case Western Reserve University.
NSF Award Number: CMMI 0727231
This award supports collaborative work by research teams from Case Western Reserve University (CWRU) and the University of Akron (UA) on fundamentals of nanocomposite formation by a "bottom-up" self-assembly approach from dispersions of polyhedral oligomeric silsesquioxane (POSS) molecules in several thermoplastic polymers. These nanocomposite materials will have the processing ease of unfilled polymers and will be suitable for manufacturing articles with micro- and nano-scale features by high-speed injection molding, fiber spinning, and thermoforming. The fundamentals developed in this work will offer superior alternatives to most "top-down" polymer nanocomposites, where orders of magnitude increase in viscosity over that of the host polymers is a norm and achieving nanoscale dispersion is a challenge. The degree of nanofiller/polymer and nanofiller/nanofiller interactions will be governed by the choice of polymer systems and POSS grades. A continuous single screw chaotic mixing device with peak shear rate in the range 50-100 /s will render POSS nanoparticles oriented in the form of spheres of ~50 nm dia, long fibrils with ~5 nm dia, and/or lamellas of ~5 nm thickness. The hierarchical structures and the nanoparticle morphology and orientation will be correlated with mechanical and thermal properties.
References
Roy, S., Lee, B. J., Kakish, Z. M., & Jana, S. C. (2012). Exploiting POSS–sorbitol interactions: issues of reinforcement of isotactic polypropylene spun fibers. Macromolecules, 45(5), 2420-2433.
Roy, S., Scionti, V., Jana, S. C., Wesdemiotis, C., Pischera, A. M., & Espe, M. P. (2011). Sorbitol–POSS interactions on development of isotactic polypropylene composites. Macromolecules, 44(20), 8064-8079.
Roy, S., & Jana, S. C. (2011, August). POSS-sorbitol interactions: Towards development of new class of polyolefin composite materials. In ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY (Vol. 242). 1155 16TH ST, NW, WASHINGTON, DC 20036 USA: AMER CHEMICAL SOC.
Sayantan, R., Lee Byoung, J., & Jana Sadhan, C. (2010). Nucleating agent assisted dispersion of POSS in PP: Properties of nanocomposite fibers and films.
Lee, B. J., Roy, S., & Jana, S. (2009, March). PP/POSS Nanocomposites: Characterization and Properties of Melt Spun Fibers. In APS March Meeting Abstracts (pp. S1-063).
B.J. Lee, S. Roy, Jana, S.C. 2009 POSS/PP nanocomposites: Characterization and properties. SPE ANTEC 67, 126-130.
Lee, B. J., & Jana, S. C. (2008). Strengthening of polyolefins by bottom-up self-assembly of POSS nanoparticles. In Annu. Pac. Tech. Conf.,[Tech. Pap.](Soc. Plast. Eng.) (Vol. 66, pp. 177-181).
Lee, B.J., Jana, S.C., Reinforcement of polyolefins by bottom-up self-assembly of POSS nanoparticles. Presented at Americas Regional Meeting, Polymer Processing Society, Charleston, SC, October 26-29, 2008.
B.J. Lee, Jana, S.C. 2008 Strengthening of polyolefins by bottom-up selfassembly of POSS nanoparticles. SPE ANTEC 66, 177-180.
Processing of self-assembled Bottom-up polymer nanocomposite materials. Presented at CMMI Grantees Conference, University of Tennessee, Knoxville, January 7-10, 2008.
Nanofibers by Gas Jet Method
2012-2020
Our group has been developing a process to produce polymeric nanofibers at 20 times higher rate per nozzle for the same diameter than electro-spinning technology. The process can produce single-component fibers, bi-component fibers with sheath-core morphologies, and bi-component fibers with side-by-side morphologies. The method exploits hydrodynamic forces and unique rheological properties of polymer solutions and polymer melts in conjunction with thermodynamics of phase separation and thermo-reversible gelation. The method provides important new options for the economical formation of multicomponent fibers with a wide range of morphologies, including single fibers, coaxial fibers of more than two polymers, side-by-side fibers, mixtures of single, side-by-side, and coaxial fibers, and multiple parallel (islands in the sea) fibers.
SEM images showing nano-knots produced in-situ
SEM image showing side-by-side morphology
Optical images showing water droplets sitting on a nanofiber mat produced from a 50:50 w/w mixture of a hydrophobic and hydrophilic polymer
References
Niknezhad, S., & Jana, S. C. (2020). Bicomponent nanofibers from core–shell nozzle in gas jet spinning process. Journal of Applied Polymer Science, 137(27), 48901.
Ghosh, M., & Jana, S. C. Fabrication of Hollow and Porous Tin-Doped Indium Oxide Nanofibers and Microtubes via a Gas Jet Fiber Spinning Process, Materials (Basel) 13 (2020) 1539.
Rajgarhia, S. S., & Jana, S. C. (2017). Effect of Solvent Volatility on Diameter Selection of Bicomponent Nanofibers Produced by Gas Jet Fiber Process Test. International Polymer Processing, 32(5), 582-589.
Rajgarhia, S., & Jana, S. C. (2017). Influence of secondary stretching on diameter and morphology of bicomponent polymer nanofibers produced by gas jet fiber process. Polymer, 123, 219-231.
Rajgarhia, S. S., & Jana, S. C. (2016, November). Comparison of Electrospinning and Gas Jet Fiber Processes for Fabrication of Bi‐Component Polymer Nanofibers from Single Solutions. In Macromolecular Symposia (Vol. 369, No. 1, pp. 8-13).
Rajgarhia, S. S., Benavides, R. E., & Jana, S. C. (2016). Morphology control of bi-component polymer nanofibers produced by gas jet process. Polymer, 93, 142-151.
Ghosh, M., & Jana, S. C. (2016). Fabrication, Morphological Evaluation, and Characterization of Semiconducting Oxide Nanofibers from Gas Jet Fiber Spinning Process. In Proceedings of the ANTEC.
Ghosh, M., & Jana, S. C. (2015). Bi-component inorganic oxide nanofibers from gas jet fiber spinning process. RSC advances, 5(127), 105313-105318.
Shang, J. H., Benavides, R. E., & Jana, S. C. (2014). Effects of polymer viscosity and nanofillers on morphology of nanofibers obtained by a gas jet method. International Polymer Processing, 29(1), 103-111.
Jana, S. C., Rajgarhia, S., Benavides, R., & Reneker, D. H. (2014). Fiber Diameter Selection in Production of Nanofibers by Gas Jet Method.
Ghosh, M., Jana, S. C., & Reneker, D. (2014). Fabrication and Morphological Evaluation of Ceramic Nanofibers from Novel Gas-Jet Fiber Spinning.
Benavides, R. E., Jana, S. C., & Reneker, D. H. (2013). Role of liquid jet stretching and bending instability in nanofiber formation by gas jet method. Macromolecules, 46(15), 6081-6090.
Benavides, R. E., Jana, S. C., & Reneker, D. H. (2012). Nanofibers from scalable gas jet process. ACS Macro Letters, 1(8), 1032-1036.
Polymeric Composite Bipolar Plates for Proton Exchange Membrane Fuel Cells
2006-2008
The bipolar plate is a multifunctional component within the PEM fuel cell stack that connects and separates individual cells, distributes fuel gas and oxygen, conducts electrical current, manages water, supports membranes and electrodes, and withstands clamping forces. Polymer composite materials can address concerns related to weight, volume, and cost of fuel cell stacks. Conventional graphite bipolar plates (Figure 1) are heavy and costly, while metals like stainless steel face corrosion issues. Polymer composite bipolar plates offer a lighter, cost-effective alternative for next-generation PEM fuel cells.
Figure 1. Graphite bipolar plate
In this work, we investigate carbon-filled thermosetting epoxy composites as an alternative material for bipolar plates to meet the US Department of Energy (DOE) targets for both in-plane and through-plane conductivity and to ensure mechanical integrity at temperatures exceeding 150ºC. These high conductivities are achieved through the synergistic effects of highly conductive expanded graphite (EG) and carbon black (CB) particles without compromising the mechanical properties of the composites. This combination provides a promising solution for next-generation PEM fuel cell applications.
Figure 2. SEM of epoxy-expanded graphite-carbon black composite
Figure 3. Electrical conductivity of epoxy-expanded graphite-carbon black composites as a function of total filler loading
References
1. Du, L., Jana, S.C. (2008). Hygrothermal Effects on Properties of Highly Conductive Epoxy/Graphite Composites for applications as bipolar plates. *J. Power Sources*, in review.
2. Du, L., Jana, S.C. (2007). Highly conductive epoxy/graphite composites for bipolar plates in proton exchange membrane fuel cells. *Journal of Power Sources*, 172, 734-741.
3. Du, L., Jana, S.C. (2007). Highly conductive epoxy composites for application as bipolar plates in proton exchange membrane fuel cells (PEMFCs). *SPE ANTEC*, 65, 235-239.
4. Du, L., Jana, S.C. (2006). Carbon-filled polymer composites bipolar plates for proton exchange membrane fuel cells (PEMFC). *SPE ANTEC*, 64, 456-460.
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