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DOE OSTI2021

Flue Gas Desulfurization (FGD) Wastewater Treatment Using Polybenzimidazole (PBI) Hollow Fiber (HF) Membranes

Polybenzimidazole (PBI) hollow fiber membranes were used to treat flue gas desulfurization (FGD) wastewater (WW) from a coal fired power plant. Membranes were tested using both single salt solutions and real FGD WW. The PBI membranes showed >99% rejection for single salt solutions of NaCl, MgCl2, CaSO4, and CaCl2 at approximately 2000 PPM (parts per million). The membranes also showed >97% rejection for FGD WW concentrations ranging from 6900 to 14,400 PPM total dissolved solids (TDS). The pH of the FGD WW was adjusted between 3.97–8.20, and there was an optimal pH between 5.31 and 7.80 where %rejection reached a maximum of >99%. The membranes were able to operate stably up to 50 °C, nearly doubling the water flux as compared to room temperature, and while maintaining >98% salt rejection.

activation energy↗

NASA NTRS1979

Ultrafine polybenzimidazole (PBI) fibers

Mats were made from ultrafine polybenzimidazole (PBI) fibers to provide an alternate to the use of asbestos as separators in fuel cells and alkaline batteries. To minimize distortion during mat drying, a process to provide a dry fibrid was developed. Two fibrid types were developed: one coarse, making mats for battery separators; the other fine, making low permeability matrices for fuel cells. Eventually, it was demonstrated that suitable mat fabrication techniques yielded fuel cell separators from the coarser alkaline battery fibrids. The stability of PBI mats to 45% KOH at 123 C can be increased by heat treatment at high temperatures. Weight loss data to 1000 hours exposure show the alkali resistance of the mats to be superior to that of asbestos.

Chenevey, E. C.↗

NASA NTRS1977

Ultralow denier polybenzimidazole (PBI) yarns

A study to determine the feasibility of preparing ultralow denier polybenzimidazole (PBI) yarns was undertaken. Conditions that presently yield multifilament yarns with bundle deniers ranging from 75 to 15,000 were used as a baseline. From this starting point, process parameters were identified that give five filament yarns with yarn densiers as low as 0.80. Physical properties from such ultralow denier yarns were at levels that would permit subsequent fabrication into fabrics.

Tan, M.↗

NASA NTRS1992

Characterization of polybenzimidazole (PBI) film at high temperatures

Polybenzimidazole, a linear thermoplastic polymer with excellent thermal stability and strength retention over a wide range of temperatures, was evaluated for its potential use as the main dielectric in high temperature capacitors. The film was characterized in terms of its dielectric properties in a frequency range of 50 Hz to 100 kilo-Hz. These properties, which include the dielectric constant and dielectric loss, were also obtained in a temperature range from 20 C to 300 C with an electrical stress of 60 Hz, 50 V/mil present. The alternating and direct current breakdown voltages of silicone oil impregnated films as a function of temperature were also determined. The results obtained indicate that while the film remained relatively stable up to 200 C, it exhibited an increase in its dielectric properties as the temperature was raised to 300 C. It was also found that conditioning of the film by heat treatment at 60 C for six hours tended to improve its dielectric and breakdown properties. The results are discussed and conclusions made concerning the suitability of the film as a high temperature capacitor dielectric.

Hammoud, Ahmad N.↗

DOE OSTI2025

Fabrication and Scale-Up of Porous Polybenzimidazole (PBI) Supports for Gas Separation Composite Membranes

Industrial gas separation often uses thin film composite (TFC) membranes comprising a porous support overlaid with a single-/multi-layer gas-selective thin film. An optimal porous support should possess high surface porosity to minimize gas transport resistance and nano-sized pores to ease pore penetration occurring during the thin film coating process. Good chemical and thermal stabilities are essential to withstand the aggressive solvents and heat required for the thin film coating and curing. However, few porous membranes satisfy all these requirements. This study presents a scalable membrane formation method of making highly porous polybenzimidazole (PBI) supports via non-solvent induced phase separation. This presentation also details the scale-up fabrication of PBI supports using a custom roll-to-roll membrane casting machine.

gas separation↗

DOE OSTI2020

Prediction of Performance Variation Caused by Manufacturing Tolerances and Defects in Gas Diffusion Electrodes of Phosphoric Acid (PA)–Doped Polybenzimidazole (PBI)-Based High-Temperature Proton Exchange Membrane Fuel Cells

The automated process of coating catalyst layers on gas diffusion electrodes (GDEs) for high-temperature proton exchange membrane fuel cells results inherently into a number of defects. These defects consist of agglomerates in which the platinum sites cannot be accessed by phosphoric acid and which are the consequence of an inconsistent coating, uncoated regions, scratches, knots, blemishes, folds, or attached fine particles—all ranging from μm to mm size. These electrochemically inactive spots cause a reduction of the effective catalyst area per unit volume (cm2/cm3) and determine a drop in fuel cell performance. A computational fluid dynamics (CFD) model is presented that predicts performance variation caused by manufacturing tolerances and defects of the GDE and which enables the creation of a six-sigma product specification for Advent phosphoric acid (PA)-doped polybenzimidazole (PBI)-based membrane electrode assemblies (MEAs). The model was used to predict the total volume of defects that would cause a 10% drop in performance. It was found that a 10% performance drop at the nominal operating regime would be caused by uniformly distributed defects totaling 39% of the catalyst layer volume (~0.5 defects/μm2). The study provides an upper bound for the estimation of the impact of the defect location on performance drop. It was found that the impact on the local current density is higher when the defect is located closer to the interface with the membrane. The local current density decays less than 2% in the presence of an isolated defect, regardless of its location along the active area of the catalyst layer.

Gurau, Vladimir (ORCID:0000000327429061)↗

DOE OSTI2022

Polybenzimidazole (PBI) membranes for redox flow batteries

Disclosed are redox flow battery membranes, redox flow batteries incorporating the membranes, and methods of forming the membranes. The membranes include a polybenzimidazole gel membrane that is capable of incorporating a high liquid content without loss of structure that is formed according to a process that includes in situ hydrolysis of a polyphosphoric acid solvent. The membranes are imbibed with a redox flow battery supporting electrolyte such as sulfuric acid and can operate at very high ionic conductivities of about 100 mS/cm or greater. Redox flow batteries incorporating the PBI-based membranes can operate at high current densities of about 100 mA/cm2 or greater.

Benicewicz, Brian C.↗

DOE OSTI2023

Polybenzimidazole (PBI) membranes for redox flow batteries

Benicewicz, Brian C.↗

DOE OSTI2022

Low permeability polybenzimidazole (PBI) gel membranes for redox flow batteries

Disclosed are redox flow battery membranes, redox flow batteries incorporating the membranes, and methods of forming the membranes. The membranes include a densified polybenzimidazole gel membrane that is capable of incorporating a high liquid content without loss of structure that is formed according to a process that includes in situ hydrolysis of a polyphosphoric acid solvent followed by densification of the gel membrane. The densified membranes are then imbibed with a redox flow battery supporting electrolyte such as sulfuric acid and can operate at very high ionic conductivities of about 50 mS/cm or greater and with low permeability of redox couple ions, e.g. vanadium ions, of about 10−7 cm2/s or less. Redox flow batteries incorporating the membranes can operate at current densities of about 50 mA/cm2 or greater.

Benicewicz, Brian C.↗

NASA NTRS1972

Flame retardant treatments of PBI fabric.

Fabrics knitted or woven from polybenzimidazole (PBI) fibers were treated to reduce flammability in oxygen atmospheres, particularly that of 5 psia oxygen. Bromination to approximately 15% weight gain of such fabrics led to markedly lower burning rates; samples brominated to over 80% weight gain were self-extinguishing in 5 psia oxygen. The loss in tensile strength of fabrics due to bromination was negligible although shrinkage was observed. Free fibers showed negligible losses on bromination. Treatment of PBI fabric with organophosphorus compounds also achieved self-extinguishing character in 5 psia oxygen but the enhanced flameproofing was largely lost on leaching. Reaction with POCl3 in pyridine led to a permanent reduction in flammability.

Temin, S. C.↗

DOE OSTI2023

NMR investigation of proton transport in polybenzimidazole/polyphosphoric acid membranes prepared via novel synthesis route

Here, in this work, we present a molecular-level view of the structural changes in polybenzimidazole (PBI) membranes doped with phosphoric acid (PA) generated by a novel membrane fabrication technique. The modified PA doped membranes displayed unprecedented ionic conductivity at elevated temperatures, comparable to the starting PBI gel membranes prepared by the commonly used PPA process, while also exhibiting enhanced mechanical properties. To elucidate the cause of these effects, we used multi-nuclear ( 1 H, 13 C, 31 P) 1D PFG, MAS and CPMAS, and 2D HETCOR magnetic resonance (NMR) techniques to characterize the structure and dynamics of the modified film and the original gel PBI membranes. 1 H diffusivity measurements show significantly enhanced proton diffusivity, both in magnitude and in lower activation energy, which were consistent with its high ionic conductivity despite the lower PA content compared to the original gel membrane. CPMAS experiments further substantiated that the location of these distinct phosphate environments as being close to the polymer network. Finally, the phosphate groups in the modified membrane were revealed to be strongly bounded to each other and to the PBI polymer backbone in contrast to the combination of weakly and strongly bounded groups of the original gel membrane.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2020

A comparative experimental study of the hygroscopic and mechanical behaviors of electrospun nanofiber membranes and solution–cast films of polybenzimidazole

This article reports a comparative experimental study of the hygroscopic and mechanical behaviors of electrospun polybenzimidazole (PBI) nanofiber membranes and solution-cast PBI films. As-electrospun nonwoven PBI nanofiber mats (with the nanofiber diameter of ~250 nm) were heat-pressed under controlled temperature, pressure and duration for the study; lab-made solution-cast PBI films and commercially available PBI films (the PBI Performance Product Inc., Charlotte, NC) were used as the control samples. Thermogravimetric and microtensile tests were utilized to characterize the hygroscopic (moisture absorption) and mechanical properties of the PBI nanofiber membranes at varying heat-pressing conditions, which were further compared to those of solution-cast PBI films. Experimental results indicated that the PBI nanofiber membranes carried slightly higher thermal stability and less hygroscopic properties than those of solution-cast PBI films. In addition, heat-pressing conditions significantly influenced the mechanical properties of the resulting PBI nanofiber membranes. The stiffness and tensile strength increase with increasing either the heat-pressing pressure or duration, and relevant mechanisms were explored. Here, the present study provides a rational understanding of the hygroscopic and mechanical behaviors of electrospun PBI nanofiber membranes and solution-cast PBI films that are beneficial to their reliable cutting-edge applications in high-temperature filtration, polymer electrolyte membranes (PEMs), etc.

25 ENERGY STORAGE↗

DOE OSTI2022

Intermediate-Temperature Proton Exchange Membranes Based on Cerium Ultraphosphate Composited with Polybenzimidazole

This paper reports the rational fabrication and structural, thermal, mechanical and electrochemical characterization of a new type of intermediate-temperature (IT) polymer-inorganic composite (PIC) proton exchange membranes (PEMs) that are made of cerium ultraphosphate (CeP 5 O 14 —CUP) as the solid-state proton conductor composited with a high-temperature (HT) polybenzimidazole (PBI) as the polymeric binder. Here, flexible PBI-CUP PIC membranes with the thickness of ~135 μ m and CUP mass fraction of up to 75% were prepared by solution-casting without additional acid-doping (e.g., phosphoric acid). The proton conductivity of the fabricated IT-PIC-PEMs was up to 5.80 × 10 –2 S cm –1 as measured from a prototype IT PEM fuel cell (PEMFC) operated at 200 °C in the humidified hydrogen and air environment. This type of IT-PIC-PEMs also demonstrated sufficient mechanical strength and flexibility, excellent thermal stability (up to 350 °C), and very good durability of the proton conductivity (within the test duration of 500 h). The present experimental study shows the promising future of the IT-PIC-PEMs for applications in various IT electrochemical processes including IT-PEMFCs, IT-electrolyzers, etc.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1979

Ultrafine PBI fibers and yarns

Gentle precisely controlled process is used to draw polybenzimidazole (PBI) fibers to denier as low as 0.17 per fiber. Yarns of lightweight fibers could be useful in applications where lightweight textiles must withstand high temperatures, corrosion, or radiation.

Leal, J. R.↗

DOE OSTI2025

Novel dense-PBI membranes for photoelectrochemical hydrogen production

Summary and main accomplishments 1. Screening of available polybenzimidazole (PBI) membranes for photoelectrochemical (PEC) hydrogen production. 2. Two main candidate membranes selected and synthesized. 3. Selected membranes characterized, including assessment of electrochemical properties (conductivity) and mechanical properties (creep and creep compliance). 4. Single cell PEC system successfully fabricated. 5. Electrochemical cell tested with initial water decomposition results obtained under ‘dark electrolysis’ conditions. 6. Recommendations given for future test and work.

Corgnale, Claudio [Greenway Energy; Greenway Energ↗

DOE OSTI2023

Development of a Pre-Combustion CO 2 Capture Process Using High-Temperature PBI Hollow-Fiber Membranes

The overall objective of this project was to evaluate the advantages of transformational polybenzimidazole (PBI) polymer hollow-fiber membrane (HFM)-based, carbon dioxide (CO 2 ) capture and purification technology at bench-scale using an actual coal-derived syngas stream from a coal gasification facility. The project was carried out over two budget periods. The technical objectives in Budget Period 1 (BP1) included preparing HFs and modules and upgrading the available skid for field testing. The technical objectives for BP2 were to field-test the skid unit with actual coal-derived syngas from an oxygen-blown gasifier to obtain performance data, update the Techno-Economic Analysis (TEA) that would assist with future process scale-up, and provide information on the design of a small pilot-scale test unit. The goal was to advance the PBI-HFM CO 2 capture and gas separation system for pre-combustion applications beyond second-generation economic performance predictions and make progress toward meeting overall fossil energy performance goals of CO 2 capture with 95% CO 2 purity at a cost of electricity (COE) 30% less than baseline capture approaches. The research program was designed with progressive technical tasks leading to both dynamic and steady-state testing of the PBI-HFM skid with actual coal-derived syngas. The work plan was to: (1) fabricate sufficient Generation-2 (GEN-2) fibers for module fabrication; (2) upgrade the fiber skid to accommodate large fiber modules for bench-scale field testing; (3) conduct dynamic and steady-state testing with coal-derived syngas from an oxygen-blown gasifier and obtain system performance data; (4) perform a TEA and environmental, health, and safety (EH&S) assessment; (5) update the State-Point Data Table, Technology Gap Analysis (TGA), and Technology Maturation Plan (TMP); (6) uninstall and return the test skid to the Recipient’s facilities; and (7) submit a Final Report that describes the results and analysis of the project research effort.

03 NATURAL GAS↗

NASA NTRS1978

Ultrathin metallized PBI paper

A study to determine the feasibility of preparing ultrathin papers with a target weight of 3.5 g/m squared from polybenzimidazole (PBI) fibrids was undertaken. Small hand sheets of target weight were fabricated. They were light brown, low density materials with sufficient strength to be readily handleable. Characterization of these sheets included strength, fold endurance, thermal gravimetric analysis in air and nitrogen and photomicrographs. Two different batches of PBI fibrids were studied and differences in fabrication performance were noted. In neither case could target weight papers be prepared using conventional paper making techniques.

Chenevey, E. C.↗

DOE OSTI2023

Finely tuning the microporosity in phosphoric acid doped triptycene-containing polybenzimidazole membranes for highly permselective helium and hydrogen recovery

High-performance polymer membranes with well-defined microporosity and size-sieving ability are especially attractive for helium and hydrogen recovery. Here, in this study, we report novel macromolecular engineering of polybenzimidazole (PBI) membranes that integrate hierarchical triptycene units for high permeability and polyprotic acid doping for size sieving via controllable manipulation of microporous architecture. The triptycene moieties disrupt chain packing and introduce additional configurational free volume, leading to significantly boosted He and H 2 permeabilities compared to previously reported PBI membranes. The acid doping resulted in crosslinked PBI membranes via hydrogen bonding and proton transfer with dramatically enhanced gas selectivities. Via adjusting the H 3 PO 4 -doping level, triptycene-based polybenzimidazole (TPBI) composite membranes (TPBI-(H 3 PO 4 ) x ) exhibit the highest gas selectivities for He enrichment (i.e., α(He/CH 4 ) = 7052 ± 156) and H 2 purification (i.e., α(H 2 /CH 4 ) = 5128 ± 110) among existing polymeric gas separation membranes. Additionally, under mixed-gas conditions at 150 °C, the TPBI-(H 3 PO 4 ) 0.98 membrane displays a H 2 permeability of 46.7 Barrer and a H 2 /CO 2 selectivity of 16, far beyond the Robeson's 2008 upper bound for H 2 /CO 2 separation. The facile and diverse tunability and excellent gas separation performance make TPBI-(H 3 PO 4 ) x membranes highly attractive for helium and hydrogen separation.

42 ENGINEERING↗