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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Thermoplastic polyurethanes with controlled morphology based on methylenediphenyldiisocyanate/isosorbide/butanediol hard segments: Thermoplastic polyurethanes with controlled morphology

Isosorbide, a cyclic, rigid and renewable diol was used as a chain extender in two series of thermoplastic polyurethanes. Isosorbide was used in combination with butane diol or alone to examine the effects on polyurethane morphology. Two series of materials were prepared -one with dispersed hard domains in the matrix of polytetramethylene ether glycol soft segments of molecular weight 1400 (at 70% soft segment concentration-SSC) and the other with co-continuous soft and hard phases at 50% SSC. Morphology of materials was studied by optical and atomic force microscopy, as well as with ultra small angle x-ray scattering (USAXS). The radius of spherical hard domains, correlation lengths, mean separation distances and boundary layer thickness were measured as a function of isosorbide content.

chain extender↗
DOE OSTI2019

Metallo‐supramolecular Crosslinked Polyurethanes

ABSTRACT The effects of incorporating metal‐binding ligands as chain extenders in polyurethane elastomers were investigated. Segmented polyurethanes based on 2 kDa poly(tetramethylene oxide) (PTMO) and 4,4‐methylenebis(cyclohexyl isocyanate) were polymerized using a two‐step process in which 2,6‐bis(1‐ethyl‐5‐(methoxymethyl)‐1H‐benzo[d]imidazol‐2‐yl)pyridine was added as a chain extender. The resulting polyurethanes were then metallated using stoichiometric amounts of Zn(II) metal salts with different counterions. The resulting metallopolymers have substantially improved Young's moduli, increased failure stress, and improved thermomechanical behavior. The materials were microphase‐separated into anisotropic hard domains within a PTMO matrix. Simultaneous small‐angle X‐ray scattering and tensile testing revealed the minority hard segment domains remain relatively intact during elongation, likely due to the strength of the metal–ligand complex. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1744–1757

Lambeth, Robert H.↗
DOE OSTI2024

Thermal Activation of Zirconium(IV) Acetylacetonate Catalysts to Enhance Polyurethane Synthesis and Reprocessing

Carbamate formation and exchange catalysts enable efficient polyurethane (PU) manufacturing, as well as emerging recycling and reprocessing methods for PU thermosets. Zirconium β-diketonate complexes, such as Zr acetylacetonate [Zr(acac) 4 ], are effective alternatives to toxic organotin catalysts that have been used for PU reprocessing. Here, we report that Zr(acac) 4 undergoes a thermally activated process in the PU network during reprocessing that transforms it into a more active carbamate exchange catalyst. This process is associated with the irreversible loss of acetylacetonate ligands and is not observed for the more sterically hindered Zr 2,2,6,6-tetramethyl-3,5-heptanedione [Zr(tmhd) 4 ] complex. Crossover experiments between PU thermoplastics indicated enhanced carbamate exchange after the thermal activation of Zr(acac) 4 in the presence of one of the PUs, whereas a sample of Zr(acac) 4 activated in the absence of the PU had no catalytic activity. Thermal gravimetric analysis suggested that this process is associated with the loss of one protonated acac ligand. Stress relaxation analysis of PU thermosets indicated a distinct change in the characteristic relaxation time associated with the thermal activation of Zr(acac) 4 at temperatures above 140 °C; no such change was observed for samples reprocessed using Zr(tmhd) 4 . Density functional theory and molecular experiments suggest that irreversible ligand exchange of acac with alkoxide or carbamate reduces the activation energy for urethane formation and reversion. Furthermore, the Zr(acac) 4 catalyst activated in the presence of a PU’s polyol precursor provided more porous and less dense PU foams compared to those made using the unactivated Zr(acac) 4 catalyst. Furthermore, these findings are important for developing improved PU synthesis and recycling processes. Thermally activating a catalyst during reprocessing may provide more nuanced control of the in-use and reprocessing characteristics of PU thermosets.

Alcohols↗
DOE OSTI2025

Life-cycle analysis of microalgae-based polyurethane foams

Polyurethane plastics are essential in many consumer and commercial products such as insulation, furniture, automotive interiors, and clothing. Pathways for producing polyurethane from microalgae offer an opportunity to reduce greenhouse gas emissions and other environmental impacts and can incorporate processes that avoid the use of toxic isocyanates typically used in conventional polyurethane production processes. In this study, the greenhouse gas emissions, fossil energy, and water consumption of biobased polyurethane and biobased non-isocyanate polyurethane were evaluated via life-cycle analysis using the R&D Greenhouse Gases, Regulated Emissions, and Energy Use in Technologies model. Microalgae-based polyurethane foam was found to achieve greenhouse gas emission reductions of up to 79% compared with conventional polyurethane foam production. The greenhouse gas reductions for the non-isocyanate microalgae polyurethane pathway are slightly lower at 58% compared with conventional polyurethane foam. However, it offers additional benefits by reducing toxicity potential compared to the isocyanate polyurethane pathway. The analysis also included a biorefinery-level analysis to evaluate the impact of incorporating polyurethane production into fuel-processing microalgae biorefineries. The sensitivity analyses conducted in this study reveal that improved algae cultivation strategies can lead to decreases of up to 127% and 80% in GHG emissions from the baseline process of Bio-PU and Bio-NIPU, respectively. Likewise, implementation of renewable electricity can result in up to 128% and 74% lower GHG emissions compared to the baseline production of Bio-PU and Bio-NIPU, respectively. Finally, the analysis evaluated different coproduct handling methods including displacement and allocation (based on mass, energy, and market-value). The results suggest that it is important to consider both the displacement and allocation methods as these led to significant differences in the environmental impacts.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Biocompatible Polyurethane Scaffolds Prepared from Glycerol Monostearate-Derived Polyester Polyol

Biodegradable polyester polyol was synthesized from oleochemical glycerol monostearate (GMS) and glutaric acid under a non-catalyzed and solvent-free polycondensation method. The chemical structure of GMS-derived polyester polyol (GPP) was elucidated by FTIR, {sup 1}H and {sup 13}C NMR, and molecular weight of GPP was characterized by GPC. The synthesized GPP with acid value of 3.03 mg KOH/g sample, hydroxyl value of 115.72 mg KOH/g sample and M{sub n} of 1345 g/mol was incorporated with polyethylene glycol (PEG) and polycaprolactone diol (PCL diol) to produce a water-blown porous polyurethane system via one-shot foaming method. The polyurethanes were optimized by evaluating glycerol as a crosslinker, silicone surfactant and water blowing agent on tensile properties of polyurethanes. All polyurethanes underwent structural change, and crystalline hard segments of polyurethanes were shifted to higher temperature suggested that hard segments undergone re-ordering process during enzymatic treatment. In terms of biocompatibility, polyurethane scaffold produced by reacting 100% w/w of GPP with isophorone diisocyanate and additives showed the highest cells viability of 3T3 mouse fibroblast (94%, day 1), and MG63 human osteosarcoma (107%, day 1) and better cell adhesion as compared to reference polyurethane produced by only PEG and PCL diol (3T3 cell viability: 8%; MG63 cell viability: 2%). The current work demonstrated GPP synthesized from renewable and environmental friendly resources produced polyurethanes that allows improvement in physico-chemical, mechanical and biocompatibility properties. By blending with increasing content of GPP, the water-blown porous polyurethane scaffold has shown great potential as biomaterial for soft and hard tissue engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Preparation, Characterization, and Antioxidant Activity of β-Carotene Impregnated Polyurethane Based on Epoxidized Soybean Oil and Malic Acid

A new polyol was synthesized based on epoxidized soybean oil (ESO) and malic acid (MA) for the formulation of a bio-based polyurethane. The synthesized polyol was characterized by Fourier transform-infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry. Polyurethanes were formed by reacting the synthesized ESO-MA polyol with 1,6-hexamethylene diisocyanate at different isocyanate/hydroxyl ratios. The tensile and thermal properties of the prepared polyurethanes were analyzed by differential scanning calorimetry, thermogravimetric analysis, and universal testing machine. The polyurethanes exhibited a tensile strength of 1.34–5.56 MPa, an elongation at break of 20–41%, and a glass transition temperature of − 2.7 to 0.6 °C. In addition, β-carotene, a natural antioxidant, was impregnated on the polyurethane surface and its effect on the tensile and thermal properties of polyurethane was investigated. An increase in tensile strength and a reduction in elongation at break were observed in these β-carotene impregnated polyurethane films. They also showed up to 61% radical scavenging activity against 2,2-diphenyl-1-picryhydrazyl radical in methanol. Moreover, these films retained radical scavenging activity for more than 50 days.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Water reactive polyurethane grouting for deep vadose zone contaminant immobilization

Contaminants in the deep vadose zone (DVZ) pose a long-term threat to groundwater, human health, and the environment. Polyurethane grouting is a type of chemical grouting that is potentially advantageous in immobilizing contaminants in DVZs. Polyurethane resin has low viscosity that makes it feasible to penetrate and fill the pore space between fine particles. Here, in this study a series of laboratory pressure grouting and leaching tests were conducted to simulate and assess the effectiveness of polyurethane grouting for immobilizing contaminants in DVZs. Soil with fine particles was prepared with 127 I (as iodide) that served as a non-radioactive surrogate for radioactive 129 I. After grouting and curing, leaching tests were used to measure and compare contaminant diffusivity and leachability index values. Additionally, changes in porosity and saturated hydraulic conductivity of grouted soil were measured. X-Ray Computer Tomography (XCT) results showed that the cured polyurethane was distributed nearly homogeneously and approximately half of the voids were filled with cured polyurethane. Grouting reduced the saturated hydraulic conductivity of soil by 37 %. The effective diffusivity decreased by more than 80 % as compared with the ungrouted soil. The leachability index of the grouted soil was 6.5; meeting the criteria established by the U.S. Nuclear Regulatory Commission (NRC) standard. The results obtained in this study provide a valuable assessment of polyurethane grouting for iodide immobilization in the DVZ and indicate this approach may be a viable method for contaminant remediation in DVZ soils.

Contaminant Diffusion↗
DOE OSTI2019

Lignin-Based Polyurethanes from Unmodified Kraft Lignin Fractionated by Sequential Precipitation

In this work, lignin-based polyurethanes were synthesized from three unmodified softwood Kraft lignin fractions as the primary hydroxyl group providers which constituted >40% of the polymeric materials. High-, medium-, and low-molecular-weight Kraft lignin fractions were prepared by sequential precipitation from the acetone–methanol cosolvent by adding hexane as an antisolvent. A polyether, poly(ethylene glycol), and a polyester, poly(trimethylene glutarate), were selected as secondary polyols to form the soft segments in the lignin-based network. At a fixed NCO/OH ratio (1:1), the effects of lignin macromolecular features and their intermolecular interactions with the secondary polyols on mechanical and thermal properties of the lignin-based polyurethanes were investigated by tensile tests, DMA, SEM, and TGA. Because of the unique association behavior of macromolecular lignin, the sequential precipitation method was able to produce Kraft lignin fractions possessing very high molecular weights. The morphological study showed that the polyurethane network was assembled by cross-linking nanosized lignin complexes through urethane links. It was discovered that the mechanical properties of the lignin-based polyurethanes can be tuned by lignin molecular weight and the incorporation of a secondary polyol. Compared to poly(trimethylene glutarate), poly(ethylene glycol) interacts strongly with associated lignin complexes through hydrogen bonding. It promoted dissociation of the lignin complexes and consequently improved reactivity between lignin and diisocyanate. Moreover, at PEG/lignin = 1:4 (w/w), the soft segments formed by PEG enhanced the stiffness of the lignin-based polyurethanes; when the PEG content was increased to PEG/lignin = 2:3 (w/w), plastic deformation can be observed for the stress–strain curves of all corresponding lignin-based polyurethanes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Polyurethanes Based on Unmodified and Refined Technical Lignins: Correlation between Molecular Structure and Material Properties

The structural complexity and robust intermolecular interactions have challenged the incorporation of technical lignin into value-added polymeric materials for decades. To study the correlation between lignin molecular structure and material properties of lignin-based polyurethanes, we applied co-solvent enhanced lignocellulosic fractionation pretreatment followed by sequential precipitation to produce three distinct lignin preparations with narrowly distributed (molecular weight dispersity <2) and comparatively low molecular weight (<1500 g/mol) from poplar biomass. Structural characterization indicated that these lignin preparations differed in average molecular chain length and stiffness as well as hydroxyl group distribution. Secondary hydroxyl group providers such as aliphatic diols and polyethers were incorporated as building blocks into the lignin-based polyurethanes to provide additional hydrogen capacity to improve the dispersion of lignin in the polyurethane network. The selected aliphatic diols and polyethers interacted with lignin molecules at different levels of strength depending on their molecular structure, and their impacts were ultimately reflected in the mechanical and thermal properties of the resulting lignin-based polyurethanes. The copolymerization of technical lignin with tailored structure and secondary hydroxyl providers could provide new strategies in formulating lignin-based/containing polyurethanes for various functional applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Unified Creep Plasticity Damage (UCPD) Model for Rigid Polyurethane Foams

Numerous experiments were performed to characterize the mechanical response of several different rigid polyurethane foams (FR3712, PMDI10, PMDI20, and TufFoam35) to large deformation. In these experiments, the effects of load path, loading rate, and temperature were investigated. Results from these experiments indicated that rigid polyurethane foams exhibit significant volumetric and deviatoric plasticity when they are compressed. Rigid polyurethane foams were also found to be very strain-rate and temperature dependent. These foams are also rather brittle and crack when loaded to small strains in tension or to larger strains in compression. Thus, a new Unified Creep Plasticity Damage (UCPD) model was developed and implemented into SIERRA with the name Foam Damage to describe the mechanical response of these foams to large deformation at a variety of temperatures and strain rates. This report includes a description of recent experiments and experimental findings. Next, development of a UCPD model for rigid, polyurethane foams is described. Selection of material parameters for a variety of rigid polyurethane foams is then discussed and finite element simulations with the new UCPD model are compared with experimental results to show behavior that can be captured with this model.

36 MATERIALS SCIENCE↗