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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Strengthening of a Polyurethane Matrix by Luffa Cylindrica Treated with TDI: Water Absorption and Mechanical Properties

Luffa Cylindrica (Luffa Aegypitiaca Miller) fibers with their surface modified by mercerization and TDI were used as a reinforcer in a polyurethane matrix. It was possible to confirm the fiber reaction with TDI by XPS and Elemental Analysis. TG, DTG, DSC, X-ray diffraction and SEM show that there is some surface modification after treatment. The mechanical properties of a polyurethane matrix (castor oil/MDI, NCO/OH = 1.0) and of a composite matrix containing 10% of fibers were compared. The composites absorb more water than pure polyurethane as a result of the hydrophilic behavior of natural fibers, but water sorption was smaller for fibers mercerized and treated with TDI. The tensile moduli observed for composites reinforced with untreated and mercerized fibers were similar but increased 35% with the use of mercerized/TDI modified fiber.TDI treatment caused an increase of 50% in maximum load compared to the polymeric matrix.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Influence of Chemical Structure of Petrochemical Polyol on Properties of Bio-polyurethane Foams

In this study, the influence of the chemical structures of petrochemical polyols on the foaming process of polyurethane compositions as well as on selected properties of the foams obtained has been investigated. Two types of petrochemical polyols were used—polyester and polyether polyols as well as their blends with a rapeseed oil-based polyol. Dielectric polarization, temperature and expansion velocity were determined during the foaming process of the polyurethane systems with different polyol components. The results show the highest reactivity of the polyester polyol and a decrease of the polyurethane system’s reactivity as a result of a partial replacement of the petrochemical polyol with the bio-based polyol. The content of the closed cells in the materials obtained strongly depends on the petrochemical polyol used. The results indicate that the chemical structure of the petrochemical polyol had a significant effect on the cellular structure as well as the physical–mechanical properties of the final products. A significant worsening of the foams’ mechanical properties was observed as an effect of a partial replacement of the polyester polyol with the rapeseed oil-based polyol. In contrast, a partial replacement of the polyether polyol caused an improvement of the cell structure keeping the mechanical properties of the modified foams at the same level.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Chloride induced reinforcement corrosion behavior in self-healing concrete with encapsulated polyurethane

Cracks in reinforced concrete structures accelerate the ingress of chlorides and therefore cause a higher risk for corrosion. In this research, autonomous healing of cracks by encapsulated polyurethane was investigated as a possible method to reduce reinforcement corrosion. Reinforced concrete beams were exposed weekly to a chloride solution and electrochemical parameters were measured to determine the influence of the self-healing mechanism on the corrosion process. The rebars were visually examined afterwards. For the cracked beams an active state of corrosion was detected within an exposure period of 10 weeks and clear pitting corrosion was observed on the rebars. Autonomous crack healing with low viscosity polyurethane could significantly reduce the corrosion in the propagation stage. For these specimens no visual damage to the rebars was detected. In conclusion, the application of self-healing concrete with a low viscosity polyurethane is able to enhance the durability of reinforced concrete structures in marine environments.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Preparation and characterization of plasticized palm-based polyurethane solid polymer electrolyte

Palm-based polyurethane solid polymer electrolyte was prepared via prepolymerization method between palm kernel oil based polyols (PKO-p) and 2,4’-diphenylmethane diisocyanate (2,4’-MDI) in acetone at room temperature with the vary amount of lithium trifuoromethanesulfonate (LiCF{sub 3}SO{sub 3}) salt and polyethylene glycol (PEG). The film was analyzed using attenuated total reflection infrared (ATR-IR) spectroscopy, electrochemical impedance spectroscopy (EIS) and X-ray diffractometry (XRD). EIS result indicated ionic conductivity obtained with 30 wt% LiCF3SO3 increased to 6.55 × 10{sup −6} S cm{sup −1} when 10 wt.% of plasticizer was added into the system. FTIR analysis showed the interaction between lithium ions and amine (-N-H) at 3600–3100 cm{sup −1}, carbonyl (-C=O) at 1750–1650 cm{sup −1} and ether (-C-O-C-) at 1150–1000 cm{sup −1} of the polyurethane forming polymer-salt complexes. The XRD result confirmed that LiCF{sub 3}SO{sub 3} salt completely dissociated within the polyurethane film with the absence of crystalline peaks of LiCF{sub 3}SO{sub 3}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Reactive, anomalous compression in shocked polyurethane foams

We present the results of plate impact experiments performed on 30%–75% porous, polymeric methylene diphenyl diisocyanate polyurethane foams. The combination of new data with those previously obtained on full-density material was used to calibrate complete equations-of-state under both inert and chemically reactive frameworks. Description of unreacted polyurethane was based on a combination of Hayes and P-α models, whereas its decomposition products were predicted via free energy minimization under the assumption of chemical and thermodynamic equilibrium. Correspondence of experiment and theory suggests that polyurethane at all densities decomposes when shocked above some threshold pressure, and that this threshold falls dramatically as a function of initial porosity. The shock locus of foams at 50% or less of theoretical maximum density was found “anomalous” in the sense that final volumes increased with pressure. We attribute this anomaly to chemical decomposition of the initial matrix to a mixture of small-molecule fluids and bulk carbon (graphite or diamond, depending on the initial density)

36 MATERIALS SCIENCE↗
DOE OSTI2014

On the feasibility of polyurethane based 3D dosimeters with optical CT for dosimetric verification of low energy photon brachytherapy seeds

Purpose: To investigate the feasibility of and challenges yet to be addressed to measure dose from low energy (effective energy <50 keV) brachytherapy sources (Pd-103, Cs-131, and I-125) using polyurethane based 3D dosimeters with optical CT. Methods: The authors' evaluation used the following sources: models 200 (Pd-103), CS-1 Rev2 (Cs-131), and 6711 (I-125). The authors used the Monte Carlo radiation transport code MCNP5, simulations with the ScanSim optical tomography simulation software, and experimental measurements with PRESAGE{sup ®} dosimeters/optical CT to investigate the following: (1) the water equivalency of conventional (density = 1.065 g/cm{sup 3}) and deformable (density = 1.02 g/cm{sup 3}) formulations of polyurethane dosimeters, (2) the scatter conditions necessary to achieve accurate dosimetry for low energy photon seeds, (3) the change in photon energy spectrum within the dosimeter as a function of distance from the source in order to determine potential energy sensitivity effects, (4) the optimal delivered dose to balance optical transmission (per projection) with signal to noise ratio in the reconstructed dose distribution, and (5) the magnitude and characteristics of artifacts due to the presence of a channel in the dosimeter. Monte Carlo simulations were performed using both conventional and deformable dosimeter formulations. For verification, 2.8 Gy at 1 cm was delivered in 92 h using an I-125 source to a PRESAGE{sup ®} dosimeter with conventional formulation and a central channel with 0.0425 cm radius for source placement. The dose distribution was reconstructed with 0.02 and 0.04 cm{sup 3} voxel size using the Duke midsized optical CT scanner (DMOS). Results: While the conventional formulation overattenuates dose from all three sources compared to water, the current deformable formulation has nearly water equivalent attenuation properties for Cs-131 and I-125, while underattenuating for Pd-103. The energy spectrum of each source is relatively stable within the first 5 cm especially for I-125. The inherent assumption of radial symmetry in the TG43 geometry leads to a linear increase in sample points within the 3D dosimeter as a function of distance away from the source, which partially offsets the decreasing signal. Simulations of dose reconstruction using optical CT showed the feasibility of reconstructing dose out to a radius of 10 cm without saturating projection images using an optimal dose and high dynamic range scanning; the simulations also predicted that reconstruction artifacts at the channel surface due to a small discrepancy in refractive index should be negligible. Agreement of the measured with calculated radial dose function for I-125 was within 5% between 0.3 and 2.5 cm from the source, and the median difference of measured from calculated anisotropy function was within 5% between 0.3 and 2.0 cm from the source. Conclusions: 3D dosimetry using polyurethane dosimeters with optical CT looks to be a promising application to verify dosimetric distributions surrounding low energy brachytherapy sources.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2025

Challenges and Perspectives in Lignin‐Derived Polyurethane Foam Synthesis

Abstract Polyurethane foams (PUFs) represent a significant segment of the polyurethane (PU) and cellular plastics industries, owing to their versatile applications and desirable properties. However, the production of PUFs heavily relies on petroleum‐derived chemicals, including polyols and isocyanates, raising critical environmental concerns. Lignin, an abundant aromatic macromolecule, offers a promising alternative for replacing petroleum‐based polyols because of its intrinsic hydroxyl groups. While efforts have been made to produce and apply various lignin‐based polyurethane foams (LPUFs), their commercialization remains limited by challenges such as low product consistency, poor technical performances, and high production costs. This study critically evaluates recent advances in the development of LPUFs, including innovative synthesis methods, functional applications, and emerging research trends. Moreover, potential strategies are discussed, such as lignin fractionation, modification, and co‐solvent assistance, for addressing the challenges. By resolving them, LPUFs could play a pivotal role in transitioning the PU industry to help achieve a circular bioeconomy.

Zhang, Mairui [Carl and Melinda Helwig Department ↗
DOE OSTI2022

Integration of polyurethane meniscus scaffold during ACL revision is not reliable at 5 years despite favourable clinical outcome

Abstract Purpose The aim of this study was to evaluate the clinical outcome at 5‐year follow‐up of a one‐step procedure combining anterior cruciate ligament (ACL) reconstruction and partial meniscus replacement using a polyurethane scaffold for the treatment of symptomatic patients with previously failed ACL reconstruction and partial medial meniscectomy. Moreover, the implanted scaffolds have been evaluated by MRI protocol in terms of morphology, volume, and signal intensity. Methods Twenty patients with symptomatic knee laxity after failed ACL reconstruction and partial medial meniscectomy underwent ACL revision combined with polyurethane‐based meniscal scaffold implant. Clinical assessment at 2‐ and 5‐year follow‐ups included VAS, Tegner Activity Score, International Knee Documentation Committee (IKDC), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Lysholm Score. MRI evaluation of the scaffold was performed according to the Genovese scale with quantification of the scaffold’s volume at 1‐ and 5‐year follow‐ups. Results All scores revealed clinical improvement as compared with the preoperative values at the 2‐ and 5‐year follow‐ups. However, a slight, but significant reduction of scores was observed between 2 and 5 years. Concerning the MRI assessment, a significant reduction of the scaffold’s volume was observed between 1 and 5 years. Genovese Morphology classification at 5 years included two complete resorptions (Type 3) and all the remaining patients had irregular morphology (Type 2). With regard to the Genovese Signal at the 5‐year follow‐up, three were classified as markedly hyperintense (Type 1), 15 as slightly hyperintense (Type 2), and two as isointense (Type 1). Conclusion Simultaneous ACL reconstruction and partial meniscus replacement using a polyurethane scaffold provides favourable clinical outcomes in the treatment of symptomatic patients with previously failed ACL reconstruction and partial medial meniscectomy at 5 years. However, MRI evaluation suggests that integration of the scaffold is not consistent. Level of evidence Level IV.

Pereira, Hélder↗
DOE OSTI2024

A chemo-mechanical model for describing sorption hysteresis in a glassy polyurethane

Abstract Hysteretic sorption and desorption of water is observed from 0 to 95% relative humidity and 298–333 K on a glassy polyurethane foam. It is postulated that sorption-induced swelling of the glassy polyurethane increases the concentration of accessible hydrogen-bonding adsorption sites for water. The accessibility of sites is kinetically controlled due to the restricted thermal motions of chains in the glassy polymer, causing a difference in accessible site concentrations during sorption and desorption. This discrepancy leads to hysteresis in the sorbed concentrations of water. A coupled chemo-mechanical model relating volumetric strain, adsorption site concentration, and sorbed water concentration is employed to describe water sorption hysteresis in the glassy polyurethane. This model not only describes the final mass uptake for each relative humidity step, but also captures the dynamics of water uptake, which exhibit diffusion and relaxation rate-controlled regimes.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Flexible polyurethanes, renewable fuels, and flavorings from a microalgae oil waste stream

Renewable polymers have become an important focus in next-generation materials, and algae biomass offers an environmentally low-impact feedstock that can serve multiple uses. This study aims to develop a scalable methodology for production of microalgae-based polyols for polyurethane synthesis from waste oils derived from algae biomass. Following separation of omega-3 fatty acids from algae oil, residual oils can offer valuable building blocks for petrochemical replacements. However, unlike vegetable oils, algae oils contain organic contaminants, including photosynthetic pigments and hydrophobic cofactors that can complicate preparative methodologies. Here we convert and purify waste streams from omega-3 depleted Nannochloropsis salina algae oil, with major components consisting of palmitic and palmitoleic acid, into azelaic acid (AA) as a building block for flexible polyurethanes, with a simultaneous production of heptanoic acid (HA) as a flavor and fragrance precursor. Conversion of free fatty acid mixtures into a soft soap allows extraction of organic contaminants, and urea complexation provides isolated palmitoleic acid, which is subsequently ozonolyzed to produce AA and HA. Bio-based polyester diols are prepared from AA via esterification to provide a polyol monomer for flexible polyurethane foam preparation. The HA co-product is modified to produce the flavoring agent methyl heptanoate and also decarboxylated to produce hexane as a renewable solvent. This scalable process can be performed on oils from multiple algal species, offering valuable monomers from a highly sustainable source.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials for the biorefinery: high bio-content, shape memory Kraft lignin-derived non-isocyanate polyurethane foams using a non-toxic protocol

Polyurethanes are among the top six polymers produced in the world and are widely used in the automotive, furniture, construction and appliance industry for their light weight, impact resistance, and insulating properties. However, the use of hazardous diisocyanates used in polyurethane formulations has led many to search for more sustainable alternatives. The lignin component of biomass has been targeted to replace the often toxic and petroleum-derived precursors to polymer synthesis in support of the biorefinery concept where natural materials are used as the feedstock for commodity plastics. The use of lignin is often hampered due to its low reactivity, heterogeneity and the necessity of employing extensive purification and/or functionalization measures to ensure materials are of comparable quality. In this report, a unique method is presented for the synthesis and processing of a non-toxic, non-isocyanate polyurethane foam utilizing unmodified Kraft lignin and a biobased curing agent. Here, raw Kraft lignin is functionalized with green organic carbonates and a non-toxic approach is taken to solubilize the precursors with a curing agent from renewable fatty acids enabling rapid gel-times. For the first time, a NIPU foam from lignin is synthesized while the structure–property relationship of different reaction mixtures is studied demonstrating shape memory capacity and 100% biobased carbon content.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Design of closed-loop recycling production of a Diels–Alder polymer from a biomass-derived difuran as a functional additive for polyurethanes

Acetalization of biomass-derived 5-hydroxymethyl furfural (HMF) with pentaerythritol produced a difuran (HPH) monomer in the presence of an acid catalyst. A recyclable polymer was then synthesized by Diels–Alder reaction of bismaleimide and the HMF-derived difuran (HPH). A polyurethane, produced from the Diels–Alder polymer has a higher glass transition temperature than a polyurethane, produced from ethylene glycol. The polyurethane, containing Diels–Alder polymer also has a self-healing ability. The Diels–Alder polymer could be hydrolyzed in acidic acetate buffer at 60 °C to produce the monomers for recycling. Each produced monomer was separated by solvent extraction, and the extracted monomers were recovered in different solvent fractions, such as aqueous, ethyl acetate, and acetone fractions. Techno economic analysis was used to assess the minimum selling price ($\$14.1$ per kg) for the primary production of Diels–Alder polymer at a feed capacity of 400 tons per year. The economic viability of the primary recovery process for the most expensive recovered monomer, bismaleimide, was assessed by calculating the minimum selling price of the bismaleimide ($\$15.2$ per kg). In conclusion, a circular closed-loop recycling production process for the Diels–Alder polymer was developed and this approach can produce the Diels–Alder polymer at $8.2 per kg when the feed capacity was 40 ktons per year.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Prompt Radiation-Induced Conductivity in Polyurethane Foam and Glass Microballoons

We performed measurements and analyses of the prompt radiation-induced conductivity (RIC) in thin samples of polyurethane foam and glass microballoon foam at the Little Mountain Medusa LINAC facility in Ogden, UT. The RIC coefficient was non-linear with dose rate for polyurethane foam; however, typical values at 1E11 rad(si)/s dose rate was measured as 0.8E-11 mho/m/rad/s for 5 lb./cu ft. foam and 0.3E-11 mho/m/rad/s for 10 lb./cu ft. density polyurethane foam. For encapsulated glass microballoons (GMB) the RIC coefficient was approximately 1E-15 mho/m/rad/s and was not a strong function of dose rate.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Analysis of Material Properties of Aged Rigid Polyurethane Foam

Polyurethane foams are organic materials which can be classified as mechanically rigid or flexible. They are chemically inert, relatively unaffected by the presence of water (cracking, swelling, absorption), and can be manufactured in densities from 3-40 lb/ft 3 . In addition, polyurethane foams have exceptional mechanical and thermal properties, which support use of polyurethane foams in the 9977 shipping packages. These packages are designed for shipment of special nuclear material and are approved for storage in the K-area complex (KAC) at Savannah River Site. Through the analysis of conditioned foams, a service life ofFR-3700 can be estimated for the storage of the 9977 packages. Thus, considering anticipated temperatures of the 9977 packages in the KAC, FR-3700 was conditioned at 160°F, 185°F, 215°F, 250°F, and 160°F with 50% relative humidity, which remains within the service temperature of-320°F - 250°F of the FR-3700 foam in the 9977 packages. Prior studies have analyzed foams after 7, 20, and 30 months of conditioning with the current study analyzing foams up to 55 months of conditioning. Considering the limited information on the effects of radiation on FR-3700, samples were irradiated with a cobalt-60 source at a high and low dose rate of 90.9 krad/hr and 16.67 krad/hr, respectively, to examine the effects of irradiation and dose rate on thermal properties. It was found that foams conditioned up to 55 months had comparable heat capacity values to FR-3700, with a slight increase due to humidity. Results suggest that fire additives began decomposing at higher conditioning temperatures, reducing the average percent mass loss. Overall, irradiation and humidity had minimal effects on thermal properties of FR-3700.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Enhanced Production of Algae Lipids and Carbohydrates for Fuel and Polyurethane Precursors

This Final Technical Report summarizes the goals, approach, and outcomes of the project “Enhanced Production of Algae Lipids and Carbohydrates for Fuel and Polyurethane Precursors”. The project addressed the challenge of improving microalgae biomass productivity and simultaneously producing valuable polyurethane precursors (PUPs), from both lipids and carbohydrates, that can be converted into renewable biofuels and bio-based polyurethane (PU) products. By integrating advanced genetic engineering, traditional breeding, high-throughput screening, pilot cultivation, and chemical conversion technologies, the team achieved significant advancements in algae biotechnology.

09 BIOMASS FUELS↗
DOE OSTI2025

Laboratory Testing to Assess the Feasibility of Polyurethane Flat Belts for Marine Energy Applications

Polyurethane flat belts have received limited scientific attention as load-bearing elements in marine energy systems, particularly in applications involving dynamic tensile and bending loads. This study evaluates their potential as a replacement for traditional wire ropes in marine energy applications, with a focus on their ability to be integrated into winch-driven wave energy converters where bending and tensile stresses can make long-term operation difficult. Polyurethane belts are hypothesized to offer enhanced fatigue resistance due to their reduced thickness in the bending plane and therefore lower bending stresses. This research involves a series of tests utilizing the National Renewable Energy Laboratory’s (NREL) Large-Amplitude Motion Platform to replicate the dynamic conditions experienced by mooring lines of winch-based point-absorber-type marine energy converters. The conditions tested include unequal coiling and uncoiling tensions and load cases resulting from the device’s unconstrained movement relative to its anchor, such as twisting and off-axis loading. Results from this study show that polyurethane flat belts can achieve more than 198 percent of the fatigue life of a conventional wire rope under similar load profiles. The stress concentrations resulting from off-axis loading and cumulative twist beyond the system’s allowable limits have been identified as potential failure modes for flat belt mooring lines used in winch-driven wave energy converters deployed in ocean environments. To mitigate these risks, the use of anti-spin systems and fairleads designed to accommodate off-axis loading while limiting twist accumulation is recommended.

13 HYDRO ENERGY↗
NASA NTRS1985

Polyurethane Masks Large Areas in Electroplating

Polyurethane foam provides effective mask in electroplating of copper or nickel. Thin layer of Turco maskant painted on area to be masked: Layer ensures polyurethane foam removed easily after served its purpose. Component A, isocyanate, and component B, polyol, mixed together and brushed or sprayed on mask area. Mixture reacts, yielding polyurethane foam. Foam prevents deposition of nickel or copper on covered area. New method saves time, increases productivity and uses less material than older procedures.

Beasley, J. L.↗
NASA NTRS2000

Uncertainty Analysis of Decomposing Polyurethane Foam

Sensitivity/uncertainty analyses are necessary to determine where to allocate resources for improved predictions in support of our nation's nuclear safety mission. Yet, sensitivity/uncertainty analyses are not commonly performed on complex combustion models because the calculations are time consuming, CPU intensive, nontrivial exercises that can lead to deceptive results. To illustrate these ideas, a variety of sensitivity/uncertainty analyses were used to determine the uncertainty associated with thermal decomposition of polyurethane foam exposed to high radiative flux boundary conditions. The polyurethane used in this study is a rigid closed-cell foam used as an encapsulant. Related polyurethane binders such as Estane are used in many energetic materials of interest to the JANNAF community. The complex, finite element foam decomposition model used in this study has 25 input parameters that include chemistry, polymer structure, and thermophysical properties. The response variable was selected as the steady-state decomposition front velocity calculated as the derivative of the decomposition front location versus time. An analytical mean value sensitivity/uncertainty (MV) analysis was used to determine the standard deviation by taking numerical derivatives of the response variable with respect to each of the 25 input parameters. Since the response variable is also a derivative, the standard deviation was essentially determined from a second derivative that was extremely sensitive to numerical noise. To minimize the numerical noise, 50-micrometer element dimensions and approximately 1-msec time steps were required to obtain stable uncertainty results. As an alternative method to determine the uncertainty and sensitivity in the decomposition front velocity, surrogate response surfaces were generated for use with a constrained Latin Hypercube Sampling (LHS) technique. Two surrogate response surfaces were investigated: 1) a linear surrogate response surface (LIN) and 2) a quadratic response surface (QUAD). The LHS techniques do not require derivatives of the response variable and are subsequently relatively insensitive to numerical noise. To compare the LIN and QUAD methods to the MV method, a direct LHS analysis (DLHS) was performed using the full grid and timestep resolved finite element model. The surrogate response models (LIN and QUAD) are shown to give acceptable values of the mean and standard deviation when compared to the fully converged DLHS model.

Hobbs, Michael L.↗