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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Fused filament fabrication of thermoplastic polyurethane composites with microencapsulated phase-change material

Here, the present study examines the thermal energy storage (TES) effectiveness and printability of microencapsulated phase-change material (MEPCM) combined with thermoplastic polyurethane (TPU) for fused filament fabrication (FFF). Two formulations were assessed: 24D MEPCM, which changes phase at 24 ° C, compounded with TPU pellets and 43D MEPCM, which changes phase at 43 ° C, integrated with TPU powder. These combinations are designed to evaluate the effectiveness of the form of the TPU (pellets versus powder) in the FFF process. The investigation includes a comprehensive analysis of thermal characteristics, encompassing phase-change temperature, latent heat of fusion, thermal conductivity, and thermal decomposition, which are assessed through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Additionally, mechanical properties, including stress-strain behavior, are examined to evaluate material suitability for TES applications, while microstructural visualization is used to provide deeper insights into material performance, structural integrity, and the quality of printed components. The 24D MEPCM and TPU pellets formulation experienced a significant loss of approximately 39.6% of PCM during filament extrusion and printing, resulting in a reduced effective latent heat. Therefore, further characterization of the pellet formulation was discontinued due to excessive leakage. In contrast, the 43D MEPCM and TPU powder formulation demonstrated minimal PCM loss, with the 60 wt.% composition achieving an effective latent heat of 132 J/g. This value represents the highest effective latent heat currently documented in the literature for PCM-polymer-composite materials produced using an FFF-based additive manufacturing process.

25 ENERGY STORAGE↗
DOE OSTI2020

Effect of 3D printing conditions on the micro- and macrostructure and properties of high-performance thermoplastic composites

Within the scope of extrusion based additive manufacturing, this chapter provides a review of the research in understanding the physical relationships between microstructure variables and macrostructure properties of high-performance thermoplastic polymers. The development of interlayer strength has been discussed based on the theory of inter-diffusion and re-entanglement of polymer chains at interface. The observations from the study in joining and direct-bonding of polymer surfaces provide insights into the mechanisms of the formation of interface between adjacent layers. Quantitative prediction of interfacial strength as a function of processing temperature and contact time is presented. The mechanisms that lead to reduced mechanical strength at the interface are discussed. The second half of the chapter outlined a set of printing conditions and their influence on structural properties.

Liu, Peng↗
DOE OSTI2021

Melt extruded versus extrusion compression molded glass-polypropylene long fiber thermoplastic composites

Long fiber thermoplastic (LFT) composites are processed either with extrusion compression or fiber injection processes. The properties of LFT materials are highly influenced by processing techniques, which lead to different porosity contents, fiber length distributions, and fiber orientation distributions. It is important to understand the various LFT processing techniques and their effects on mechanical, thermal, and microscopic properties. This work considered LFT sheets processed via extrusion, which offers highly aligned fibers (referred to as “Tecnogor composites”), and LFT composites produced via extrusion compression molding (ECM), which offers a random distribution of fibers. Tecnogor composites exhibited higher flexural strength (35–65%), flexural modulus (132–172%), tensile strength (39–52%), tensile modulus (67–75%), and Izod impact resistance (195–220%) than the random LFT composites. This response was attributed to the aligned fibers in Tecnogor composites. Mathematical models including Halpin-Tsai and Lavengood-Goettler were used to predict and compare the Young’s modulus of Tecnogor and ECM composites, respectively.

mechanical testing↗
DOE OSTI2023

Conductive overbraid of continuous fiber thermoplastic composite tows

Here, to meet the increasing demand for lightweight materials with multifunctional capabilities, a new high-rate manufacturing method and material system, referred to as M-TOW ® (multifunctional-tow) is introduced. Overbraiding is used to incorporate highly conductive wire onto the continuous fiber reinforced tow (M-TOW ® ), offering a solution for integrating thermal and electrical conductivity into hybrid-molded composite structures. The conductivity performance of different wire configurations are compared before and after forming the M TOW ® , measuring electrical conductivities up to 5.5 x 10 5 S / cm and thermal conductivities up to 21 W / mK. Results conclude that the integration of conductive wires into thermoplastic preforms is a viable means of expanding the functionality of lightweight, high strength composite structures.

3-dimensional reinforcement↗
DOE OSTI2024

Examining infrared thermography based approaches to rapid fatigue characterization of additively manufactured compression molded short fiber thermoplastic composites

A novel additive manufacturing (AM) methodology combined with a compression molding (CM) process has been developed to optimize the microstructure of short fiber thermoplastic composites (SFTs)with higher fiber alignment and lower porosity, yielding superior stiffness, strength, and structural integrity. Here, the current work examines the efficacy of the ‘passive’ infrared thermography (IRT) techniques for rapid fatigue characterization of SFTs that use the surface temperature evolution during cyclic loading due to self-heating as a fatigue indicator. A comparison of fatigue limits obtained from traditional stress-life (SN) (≈53.1%σ uts ) and IRT (≈54.1%σ uts ) shows a close match. However, the SN curve required 18 specimens and two weeks of continuous cyclic testing, while IRT used three specimens with 5 hours of testing. Thus, the IRT approach provides an accelerated testing framework for rapidly estimating the fatigue limit. Additionally, existing phenomenological approaches to IRT fatigue characterization have been examined.

42 ENGINEERING↗
DOE OSTI2025

Fast-rate joining of thermoplastic composites using integrated additive manufacturing and compression molding process

The integration of additive manufacturing (AM) technology with compression molding (CM), has emerged as a high-performance composite manufacturing technology in recent years. In the AM-CM process, quickly deposited AM preform on a mold undergoes a rapid compaction cycle to fabricate structurally robust composite parts due to highly controlled fiber alignment (from AM) and reduced porosity (from CM). Currently, AMCM-based part size is limited by the size of the mold volume, thus posing a challenge to manufacture scalable parts. Here, this work focuses on joining techniques developed to enable fast rate joining of short fiber-reinforced thermoplastic composite parts using the AM-CM process. Acrylonitrile butadiene styrene resin reinforced with 20 wt% short carbon fiber composites was printed onto a flat mold and pressed under a hydraulic press. Fabricated panels were joined by the (a) mechanical impression at the joining interface and (b) over-molded continuous carbon fiber (CCF) sheet. Tensile tests were performed to characterize the joining strength of both mechanical impression-based joints and CCF over molded joints. Among the mechanical impression-based joints, a U-shape channel allowed the fibers to flow between two joint parts, and 280 % increased mechanical properties were observed. The continuous carbon fiber-based over molded joint CCF showed 350 % increase in tensile strength compared to the butt joints.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of natural carbon filler on thermo-oxidative degradation of thermoplastic-based composites

Here thermo-oxidative degradation of thermoplastic-based composites filled with two types of carbon filler including bituminous (Pittsburgh No.8, P8) and sub-bituminous (Powder River Basin, PRB) coals were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis. Oxidation induction time (OIT) and activation energy (AE) for coal plastic composites (CPCs), HDPE, and commercially available wood plastic composites (WPCs) were determined using isothermal and isoconversional kinetic methods. OIT values for CPC increased with coal content, indicating higher thermo-oxidative stability. AE values obtained using isothermal method were 52–116 kJ/mol for all CPC formulations, 32 kJ/mol for HDPE, and 33–114 kJ/mol for WPCs. AEs for CPCs obtained using isoconversional methods were not constant but rather dependent on the degree of degradation with CPC/ P8 coal possessing higher overall AE. Incorporating coal into HDPE increased thermo-oxidative stability of the resulting composite, indicating coal potentially acts as a natural primary and secondary antioxidant for polymer materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Asymmetric Miktoarm Star Polymers as Polyester Thermoplastic Elastomers

A library of polyester-based A(BA') n asymmetric miktoarm star polymers was synthesized with A, A' = poly(l-lactide) (PLLA) as the semicrystalline hard blocks and B = poly(4-methylcaprolactone) (PMCL) as the soft segment using a grafting-through platform known as μSTAR. The synthetic versatility of μSTAR enabled a systematic investigation of architectural design parameters, in particular the number of BA' arms (n), while holding the A, A', and B block lengths constant. The value of n has a pronounced impact on the mechanical properties of these high-molecular-weight miktoarm materials. Tensile toughness increases with n, an effect likely related to bridging, as the modulus drops because the hard-block volume fraction decreases. Furthermore, these insights expand our understanding of architecture effects in sustainable thermoplastic elastomers.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Synthesis, Properties, and Metathesis Activity of Polyurethane Thermoplastics and Thermosets from a Renewable Polysesquiterpene Diol

Polyurethanes (PUs) are the sixth most commonly utilized plastic class, yet ∼80% of commodity material is landfilled or incinerated at the end of life. Disposal of thermosets is particularly problematic as cross-linking prevents the repurposing of disposed material. Thus, there is considerable interest in the development of PUs derived from inexpensive feedstocks that can be inherently chemically deconstructed. Ring opening metathesis polymerization (ROMP) of the naturally occurring sesquiterpene β-caryophyllene in the presence of dihydroxy chain terminators afforded the polyol hydroxy-terminated polycaryophyllene (HTPCR). Incorporation of HTPCR into PUs through reaction with polyisocyanates produced polymers with thermal and rheological properties comparable to commodity materials. The feasibility of chemical degradation of both thermoplastic and thermoset materials was also demonstrated through ruthenium-mediated metathesis, utilizing the metathesis-active olefins within the repeat caryophyllene monomer unit. Overall, this work highlights the value of biorenewable, chemically reprocessable polysesquiterpenes in the PU space.

materials↗
DOE OSTI2023

Revealing Deformation Mechanisms in Polymer-Grafted Thermoplastic Elastomers via In Situ Small-Angle X-ray Scattering

The tunable properties of thermoplastic elastomers (TPEs), through polymer chemistry manipulations, enable these technologically critical materials to be employed in a broad range of applications. The need to “dial-in” the mechanical properties and responses of TPEs generally requires the design and synthesis of new macromolecules. In these designs, TPEs with nonlinear macromolecular architectures outperform the mechanical properties of their linear copolymer counterparts, but the differences in the deformation mechanism providing enhanced performance are unknown. Here, in situ small-angle X-ray scattering (SAXS) measurements during uniaxial extension reveal distinct deformation mechanisms between a commercially available linear poly(styrene)–poly(butadiene)–poly(styrene) (SBS) triblock copolymer and the grafted SBS version containing grafted poly(styrene) (PS) chains from the poly(butadiene) (PBD) midblock. The neat SBS (φ SBS = 100%) sample deforms congruently with the macroscopic dimensions, with the domain spacing between spheres increasing and decreasing along and transverse to the stretch direction, respectively. At high extensions, end segment pullout from the PS-rich domains is detected, which is indicated by a disordering of SBS. Conversely, the PS-grafted SBS that is 30 vol % SBS and 70% styrene (φ SBS = 30%) exhibits a lamellar morphology, and in situ SAXS measurements reveal an unexpected deformation mechanism. During deformation, there are two simultaneous processes: significant lamellar domain rearrangement to preferentially orient the lamellae planes parallel to the stretch direction and crazing. The samples whiten at high strains as expected for crazing, which corresponds with the emergence of features in the 2D SAXS pattern during stretching consistent with fibril-like structures that bridge the voids in crazes. The significant domain rearrangement in the grafted copolymers is attributed to the new junctions formed across multiple PS domains by the grafting of a single chain. In conclusion, the in situ SAXS measurements provide insights into the enhanced mechanical properties of grafted copolymers that arise through improved physical cross-linking that leads to nanostructure domain reorientation for self-reinforcement and craze formation where fibrils help to strengthen the polymer.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Corrosion Resistance of Lignin-Based Thermoplastic Adhesive-Bonded Aluminum Joints

Adhesive-bonded joints are essential for lightweight, multimaterial automotive structures. We developed a lignin-based thermoplastic adhesive with adhesion strength comparable to conventional epoxy adhesives (20–23 MPa), while offering exceptional durability, recyclability, and corrosion resistance. Unlike commercial epoxy adhesives requiring refrigerated storage, our adhesive retains its bonding potential after a year of ambient conditioning. Bonded joints can be repeatedly disassembled and rejoined with less than 2% strength loss. After 500 h of salt fog exposure, the adhesive-bonded aluminum joints exhibited a 24% strength reduction, compared to 61% reduction in strength of joints based on a commercial epoxy adhesive.

Yu, Zeyang [ORNL] (ORCID:0000000209002374)↗
DOE OSTI2025

Commodity Thermoplastic Elastomer-Enabled Templated Synthesis of Large-Pore Ordered Mesoporous Materials

Fabrication of ordered mesoporous materials (OMMs) has predominantly relied on templating-based methods. However, these methods are constrained by several limitations, especially the limited pore sizes attainable with commercially available surfactants used as structure-directing agents. To unlock the full potential of the OMMs, it is essential to develop synthetic strategies that facilitate the production of large-pore OMMs using scalable processes and cost-effective precursors. This work demonstrates the use of thermoplastic elastomer (TPE)-derived carbon replicas for synthesizing ordered mesoporous silica (OMS) and metal oxides (OMMOs) via precursor infiltration and template removal. The nanostructural evolution of the resulting inorganic materials was systematically investigated. Specifically, using tetraethyl orthosilicate (TEOS) as a silica precursor, this method can produce an OMS with relatively large pores. To establish the generalizability of this process, the fabrication approach was extended to other commercially available TPEs with varied chemical compositions and molecular weights while consistently resulting in ordered structures. Additionally, this synthetic strategy can be successfully applied to the production of OMMOs, including tin and titanium oxide matrix chemistries, yielding pore sizes of 16.0 and 19.2 nm, respectively. By developing a general method and using low-cost precursors, this work presents a scalable approach for fabricating large-pore OMMs with tunable pore textures and matrix chemistries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Direct synthesis of ordered mesoporous materials from thermoplastic elastomers

Abstract The ability to manufacture ordered mesoporous materials using low-cost precursors and scalable processes is essential for unlocking their enormous potential to enable advancement in nanotechnology. While templating-based methods play a central role in the development of mesoporous materials, several limitations exist in conventional system design, including cost, volatile solvent consumption, and attainable pore sizes from commercial templating agents. This work pioneers a new manufacturing platform for producing ordered mesoporous materials through direct pyrolysis of crosslinked thermoplastic elastomer-based block copolymers. Specifically, olefinic majority phases are selectively crosslinked through sulfonation reactions and subsequently converted to carbon, while the minority block can be decomposed to form ordered mesopores. We demonstrate that this process can be extended to different polymer precursors for synthesizing mesoporous polymer, carbon, and silica. Furthermore, the obtained carbons possess large mesopores, sulfur-doped carbon framework, with tailorable pore textures upon varying the precursor identities.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Rapid biodegradation of microplastics generated from bio-based thermoplastic polyurethane

The accumulation of microplastics in various ecosystems has now been well documented and recent evidence suggests detrimental effects on various biological processes due to this pollution. Accumulation of microplastics in the natural environment is ultimately due to the chemical nature of widely used petroleum-based plastic polymers, which typically are inaccessible to biological processing. One way to mitigate this crisis is adoption of plastics that biodegrade if released into natural environments. In this work, we generated microplastic particles from a bio-based, biodegradable thermoplastic polyurethane (TPU-FC1) and demonstrated their rapid biodegradation via direct visualization and respirometry. Furthermore, we isolated multiple bacterial strains capable of using TPU-FC1 as a sole carbon source and characterized their depolymerization products. Finally, to visualize biodegradation of TPU materials as real-world products, we generated TPU-coated cotton fabric and an injection molded phone case and documented biodegradation by direct visualization and scanning electron microscopy (SEM), both of which indicated clear structural degradation of these materials and significant biofilm formation.

09 BIOMASS FUELS↗
DOE OSTI2023

Tunable thermoplastic elastomer gels derived from controlled-distribution triblock copolymers with crystallizable endblocks

Thermoplastic elastomers (TPEs), a commercially important category of triblock copolymers, are employed alone or upon physical modification with a midblock-selective oil (to form TPE gels, TPEGs) in a broad range of contemporary technologies. While most copolymers in this class of self-networking macromolecules possess glassy polystyrene endblocks and a rubbery polydiene or polyolefin midblock, we investigate TPEGs fabricated from a novel controlled-distribution copolymer with crystallizable polyolefin endblocks and a random-copolymer midblock. According to both electron microscopy and small-angle scattering, the morphologies of these TPEGs remain largely invariant up to 40 wt% oil and then transform considerably at higher oil levels. Although reductions in endblock melting point and crystallinity measured by thermal calorimetry accompany increasing oil content, mechanical properties such as the uniaxial strain at break and fracture toughness improve in some cases by over 50% between 5 and 40 wt% oil. In fact, the strain at break can reach 2500% within this range, thereby confirming that (i) the structure–property relationships of these unique TPEGs are highly composition-tunable and (ii) these TPEGs, stabilized by crystallizable endblocks, provide an attractive alternative for ultrasoft and stretchy recyclable materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Tunable polyvinyl chloride (PVC) and thermoplastic polyurethane (TPU)-based soft polymer gel sensors

Abstract Polyvinyl chloride (PVC) gels have recently been found to exhibit mechanoelectrical transduction under mechanical deformation. These mechanoelectrical properties of PVC gels are largely uncharacterized and the underlying transduction mechanisms are currently unknown. These soft electroactive polymers have tunable properties such as modulus and response voltage based on physical dimensions and the amount of plasticizer content within the material making them ideal candidates for complaint sensors. This study aims to investigate PVC gels comprised of various plasticizers to further investigate underlying mechanisms of mechanoelectrical transduction and broaden possible sensing applications. Plasticizers used in this study include dibutyl adipate, dibutyl phthalate, dioctyl phthalate, otherwise known as bis(2-ethylhexyl) phthalate, diisodecyl adipate, and the environmentally friendly biodegradable plasticizer acetyl tributyl citrate (ATBC). ATBC is often used in cosmetics and food packaging applications and is even used as a food additive which may lead to future biocompatibility for these gel sensors. These plasticizers are used to produce PVC gel sensors that are experimentally tested for mechanoelectrical transduction properties and sensing performance. In this study, a Langmuir adsorptive model is fit to the collected mechanoelectrical transduction data. These results are also nondimensionalized and compared to the characteristic dimensionless Langmuir adsorptive model. This simple model agrees very well with the experimental data. Additionally, a study on the mechanoelectrical transduction of an alternative polymer lattice structure, thermoplastic polyurethane (TPU), is discussed. This is a novel electroactive polymer investigated for mechanoelectrical transduction properties. This portion of the study aims to further knowledge of underlying mechanisms of mechanoelectrical transduction as well as show feasibility of additional lattices for soft polymer gel sensors. These TPU gel sensors show strikingly similar mechanoelectrical transduction properties to analogous PVC gels, insinuating that the polymer structure has a limited role in the underlying sensing mechanism and PVC itself is not unique to polymer gel sensing. The TPU-based soft polymer gel sensors however do display some level of mechanoelectrical hysteresis which may be attributed to viscoelastic properties and display a small amount of fatigue possibly due to exudation of liquid plasticizer. This study provides further characterization of mechanoelectrical response for varying plasticizers, provides a theoretical framework for underlying mechanisms, and displays the potential for further polymeric gel sensors.

Instruments & Instrumentation↗