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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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11 records

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NASA NTRS2008

Polybenzoxazole-filled nitrile butadiene rubber compositions

An insulation composition that comprises at least one nitrile butadiene rubber (NBR) having an acrylonitrile content that ranges from approximately 26% by weight to approximately 35% by weight and polybenzoxazole (PBO) fibers. The NBR may be a copolymer of acrylonitrile and butadiene and may be present in the insulation composition in a range of from approximately 45% by weight to approximately 56% by weight of a total weight of the insulation composition. The PBO fibers may be present in a range of from approximately 3% by weight to approximately 10% by weight of a total weight of the insulation composition. A rocket motor including the insulation composition and a method of insulating a rocket motor are also disclosed.

Gajiwala, Himansu M.↗

DOE OSTI2024

Phase field modeling of hydrogen release in nitrile-butadiene rubber composites after high-pressure hydrogen exposure

Experimental data showed that a simple diffusion model doesn’t suffice to explain the hydrogen (H 2 ) release kinetics in nitrile butadiene rubber (NBR) composites (one with no filler or plasticizer, one with plasticizer only, one with fillers and plasticizer, and one with fillers only) after exposed to hydrogen gas at a pressure of 27.6 MPa. In this work, we developed a phase field model that considers the effect of H 2 gas bubble evolution on H 2 release kinetics. With the model, we simulated the effect of thermodynamic and kinetics properties on the nucleation, growth, and shrinkage of gas bubbles and H 2 release kinetics during and after decompression. Here, the results demonstrated that 1) the model built upon certain thermodynamic and kinetics properties of a given material can well describe its H 2 release kinetics measured in experiments, and 2) the model can predict the gas bubble evolution, which is associated with the material property degradation and failures, with accurate thermodynamic and kinetics properties or H 2 release data from experiments.

08 HYDROGEN↗

NASA NTRS2015

Advanced Booster Composite Case/Polybenzimidazole Nitrile Butadiene Rubber Insulation Development

The NASA Engineering and Safety Center (NESC) was requested to examine processing sensitivities (e.g., cure temperature control/variance, debonds, density variations) of polybenzimidazole nitrile butadiene rubber (PBI-NBR) insulation, case fiber, and resin systems and to evaluate nondestructive evaluation (NDE) and damage tolerance methods/models required to support human-rated composite motor cases. The proposed use of composite motor cases in Blocks IA and II was expected to increase performance capability through optimizing operating pressure and increasing propellant mass fraction. This assessment was to support the evaluation of risk reduction for large booster component development/fabrication, NDE of low mass-to-strength ratio material structures, and solid booster propellant formulation as requested in the Space Launch System NASA Research Announcement for Advanced Booster Engineering Demonstration and/or Risk Reduction. Composite case materials and high-energy propellants represent an enabling capability in the Agency's ability to provide affordable, high-performing advanced booster concepts. The NESC team was requested to provide an assessment of co- and multiple-cure processing of composite case and PBI-NBR insulation materials and evaluation of high-energy propellant formulations.

Gentz, Steve↗

DOE OSTI2025

Sustainable Shape Memory Elastomers with Reduced Melt Viscosity and Enhanced Stiffness

Melt reactive processing of lignin with nitrile rubber is a promising approach to synthesizing shape memory materials. The strong intramolecular interactions in lignin macromolecular structures, caused by π–π stacking in aromatic rings and hydrogen bonding, often result in large phase separation or low miscibility with rubbers. In this study, we investigated the chemical and molecular characteristics, as well as the stiffness and complex viscosity, of modified kraft lignin melt-reacted with an acrylonitrile/butadiene copolymer containing 41% acrylonitrile (NBR41). To enhance the macromolecular compatibility of kraft lignin with NBR41, kraft lignin was cross-linked with poly(propylene glycol) diglycidyl ether (PPDE) and trimethylolpropane triglycidyl ether (TTE), both rich in epoxy reactive groups capable of forming chemical bonds with hydroxyl and carboxyl groups. Here, our findings demonstrate that the modification of kraft lignin with PPDE and TTE resulted in significantly increased stiffness of the composites. The elastic modulus of NBR41-Kraft lignin-PPDE and NBR41-Kraft lignin-TTE increased by 82 and 162%, respectively. Both the yield strength and Young’s modulus of these two samples showed dramatic improvements. Specifically, the yield strength and Young’s modulus of NBR41-Kraft lignin-TTE increased nearly 4 and 3-fold, respectively, compared to the control sample. Interestingly, despite significant improvements in mechanical properties, the viscosity of NBR41-Kraft lignin-PPDE was substantially lower than that of the control sample. At 210 °C and an angular frequency of 1 rad/s, the complex viscosity of NBR41-Kraft lignin was approximately 100.25 ± 4.77 kPa·s, while that of NBR41-Kraft lignin-PPDE was significantly lower at 56 ± 0.93 kPa·s. These findings were validated through Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic mechanical analysis, thermal characterization, rheological tests, and quasi-elastic neutron scattering techniques.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2010

Basalt fiber and nanoclay compositions, articles incorporating the same, and methods of insulating a rocket motor with the same

An insulation composition that comprises at least one nitrile butadiene rubber, basalt fibers, and nanoclay is disclosed. Further disclosed is an insulation composition that comprises polybenzimidazole fibers, basalt fibers, and nanoclay. The basalt fibers may be present in the insulation compositions in a range of from approximately 1% by weight to approximately 6% by weight of the total weight of the insulation composition. The nanoclay may be present in the insulation compositions in a range of from approximately 5% by weight to approximately 10% by weight of the total weight of the insulation composition. Rocket motors including the insulation compositions and methods of insulating a rocket motor are also disclosed.

Gajiwala, Himansu M.↗

NASA NTRS2011

Rocket motors incorporating basalt fiber and nanoclay compositions and methods of insulating a rocket motor with the same

Gajiwala, Himansu M.↗

NASA NTRS1984

Constituent Property - Composite Property Relationships in Thermoset Matrices

A procedure to effectively screen and evaluate resins for aerospace structures and advanced composites is described. The following conclusions were advanced: (1) laminate damage tolerance correlates positively with neat resin G sub IC; (2) TGDDM/DDS resins can be toughened; (3) using butadiene-nitrile rubbers, neat resin G sub IC and ultimate strain increase with increasing nitrile content, with the number of chemically reactive groups per molecule, and with increasing molecular weight; (4) better balance of properties combined with high G sub IC may be achieved by using tough glassy thermoplastics instead of rubbers to modify TGDDM/DDS resins; (5) both toughening mechanisms require good phase separation with an effective interphase; (6) the kind and the amount of thermoplastic modifier remain to be selected; and (7) presently only about a fourfold increase in G sub IC was achieved, whereas a forty fold increase is sought; modification of the matrix backbone and of crosslinking is required.

Diamant, J.↗

DOE OSTI2022

Nitrile-Containing Renewable Polymers Based on Lignin, (CRADA) No. NFE 1807437 (CRADA Final Report)

Lignin remains one of the world’s largest sources of renewable carbon, with significant potential to positively impact our carbon footprint by replacing fossil-fuel derived materials, including engineering thermoplastics and their composites. Efforts to incorporate significant quantity of lignin into engineering thermoplastics as anything other than an inert filler have to date been largely unsuccessful, however due to limitations imposed by the degradation temperature of the lignin (220 °C) and poor compatibility between the lignin and non-polar or slightly polar polymers. Recent work at Oak Ridge National Laboratory has however shown under the right conditions excellent compatibility between lignin and nitrile containing rubber compounds such as nitrile-butadiene rubber (NBR). The present work extends these findings to the incorporation of lignin into acrylonitrile-butadiene-styrene (ABS) engineering plastics. While simple binary mixing of lignin into commercial ABS resins leads to poor interfacial adhesion and resultant low toughness and ductility, appropriate matching of the lignin and ABS components, and as appropriate compatibilizing agents, leads to polymer blends incorporating 20-35% by weight lignin with a useful range of mechanical properties for many current ABS applications. By modifying the composition, the balance of properties can be readily tailored to meet the demands of specific end-user applications.

36 MATERIALS SCIENCE↗

NASA NTRS2001

Use of GC/MS and Microtome Techniques as Methods to Evaluate ODC Free Cleaner Diffusion and Evaporation in Insulation and Phenolic Case Material

Because of the 1990 Clean Air Act Amendment (CAAA) many chlorinated solvents used in the aerospace industry are being phased out. Replacement of the ODC (ozone-depleting chemicals) with less volatile, non-ozone depleting cleaners has been extensively studied over the past seven years at Thiokol Propulsion, a Division of Cordant Technologies, Inc. The down selection of ODC replacement cleaners has been based on several factors including the diffusion evaporation of the cleaners in selected substrates. Methodologies were developed to evaluate the cleaner content in substrates. Methods of cutting thin slices of material (microtoming) were combined with GC/MS (gas chromatography/mass spectroscopy) analysis. Substrates evaluated in this study include potential solid rocket motor materials: ASNBR (asbestos-filled nitrile butadiene rubber) and CFEPDM (carbon-filled ethylene propylene dimonomer) insulation and glass (GCP), carbon (CCP) and silica (SCP) cloth phenolic substrates with fibers either parallel (0 deg) or perpendicular (90 deg) to the surface. Residue profiles indicate both cleaner and substrate composition affect the diffusion and subsequent evaporation of the cleaner from the substrate surface.

Biegert, L. L.↗

DOE OSTI2023

A renewable lignin-based thermoplastic adhesive for steel joining

Adhesive bonding of metals has become increasingly relevant in recent years due to the demand for reducing weight and improving performance in structural applications such as automobiles and aerospace. We developed renewable thermoplastic adhesives from technical organosolv lignin isolated from hardwood biomass and acrylonitrile butadiene co-polymer rubber (NBR) for joining steel substrates. NBR33, NBR41 and NBR51 with acrylonitrile molar ratios of 33, 41 and 51%, respectively, were blended with lignin to form two-phase thermoplastic adhesives, and their adhesion, viscoelastic and surface properties were measured. Lignin content in the compositions were varied, ranging from 40% to 80% (w/w), to alter toughness, stiffness, and surface energy characteristics of the material. Better interaction or reactivity between the lignin and NBR phases was observed with greater nitrile content in NBR, leading to greater modulus and stiffness of the adhesive. Simultaneously, increasing the proportion of lignin reduced toughness and improved stiffness, with the highest adhesive strength of 13.1 MPa measured in a 60% lignin loading ratio with NBR51. Surface energy measurements revealed that total surface energy (sum of polar and dispersive surface energy) raised with lignin loading, suggesting that both surface energy and matrix strength play a critical role in the adhesive properties of the synthesized materials. A finite element-based cohesive zone model (CZM) was developed and implemented to study the failure strength of the adhesively bonded joint. Here, this study demonstrates the viability of lignin as a valuable building block for adhesives, not only due to its inherent chemical structure and rigidity, but also for its surface energy characteristics.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Effects of graphene surface functionalities towards controlled reinforcement of a lignin based renewable thermoplastic rubber

In this report, we describe methods to enhance mechanical properties of a renewable thermoplastic rubber by incorporating functional graphene platelets into an equal-mass mixture of lignin, a feedstock from plant biomass, and a nitrile-butadiene rubber having 41 mol % acrylonitrile content (NBR41) that form a nanocomposite. Not all lignins yield mechanically strong material when they are combined with NBR41, and thus, limit its use for such rubbery products. Here, we evaluate different graphene oxides (GO) and reduced graphene oxides (rGO) dry-powders with different surface areas, functionality, and wettability in the synthesis of performance-enhanced nanocomposites of soft lignin/NBR41 matrix via a solvent-free, high shear reactive process. High surface area GO (HSGO) platelets with strong hydrophilicity exhibit good dispersion in the multiphase lignin/NBR41 composites with lignin dispersion varying from 200 to 2000 nm, resulting in superior reinforcement over other graphene derivatives. The addition of 1–4 wt % HSGO increased the tensile stress of the lignin/NBR41 thermoplastic rubber matrix by 60–160% (15–24 MPa) and the modulus by 200–700% (60–140 MPa). Scanning electron microscopy and small angle X-ray scattering results show that the well-dispersed HSGO platelets effectively disrupt the lignin-rich aggregates in NBR41 matrix, resulting in both strength and stiffness enhancements in the formed nanocomposites. This report on performance enhancement of lignin-based renewable polymers via the production of nanocomposite would increase potential for ‘finding the value of lignin’—a grand challenge associated with modern biorefineries.

36 MATERIALS SCIENCE↗