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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A Study on Recycled Polymers Recovered from Multilayer Plastic Packaging Films by Solvent–Targeted Recovery and Precipitation (STRAP)

Multilayer plastic film use increased in multiple packaging applications due to its versatility and overall increased performance over monolayer structures. However, the performance gains from multiple layers also make recycling difficult because they contain multiple polymers that can be immiscible and burdensome to traditional mechanical recycling operations. A possible solution is the solvent-targeted recovery and precipitation (STRAP) process, but the effect on the retrieved polymer is still unknown. Here, the STRAP process is applied to two different multilayer films and samples of recovered polymers are evaluated for physical, molecular, and thermal properties. Changes in the molecular weight are not significant, but differences in thermal properties are reported along with the coprecipitation of different polymers. Solvent retention in the polymer matrix from STRAP reduced the glass transition temperature of samples, but enhanced drying recovered it. Heavy metals, such as Cd, Cr, and Pb are not detected, indicating regulatory compliance for different applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Effects of Copolymer Structure on Enzyme-Catalyzed Polyester Recycling

Polyesters are an omnipresent material used for a variety of applications (e.g., bottles, packaging, textile, windshield), roughly comprising 8% of plastics produced worldwide. Enzymatic recycling is an emerging solution to deal with the increasingly diverse polyesters that are not suitable for mechanical recycling. However, enzyme activity and efficiency are still the limiting factors impeding enzymatic recycling for different plastic waste forms. The effects of thermal and structural properties (e.g., glass transition temperature, crystallinity, specific surface area), which are determined by chemical composition and preprocessing, directly influence enzyme recycling efficiency. This work investigates two extrusion methods (single screw and twin-screw extrusion) to pretreat a range of copolyesters (RPET, PETG, Ecozen, Tritan and PBT) and modify their properties (i.e., glass transition temperature (T g ), crystallinity (%), and molecular weight (M n )). A PET-specific enzyme, leaf-branch compost cutinase (LCC ICCG ), produced from a fed-batch fermentation of Escherichia coli BL21(DE3), was used for the enzymatic depolymerization of different polyesters. Several copolyesters showed improved depolymerization after pretreatment, as measured by rate and amount of monomers produced. Furthermore, those that did not depolymerize were found to have exceptionally high glass transition temperature or percent crystallinity, highlighting the importance of these physical parameters on conversion efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Chemical recycling of mixed textile waste

Globally, less than 0.5% of postconsumer textile waste is recycled, with the majority incinerated or ending up in landfills. Most postconsumer textiles are mixed fibers, complicating mechanical recycling due to material blends and contaminants. Here, we demonstrate the chemical conversion of postconsumer mixed textile waste using microwave-assisted glycolysis over a ZnO catalyst followed by solvent dissolution. This approach electrifies the process heat while allowing rapid depolymerization of polyester and spandex to their monomers in 15 minutes. A simple solvent dissolution enables the separation of cotton and nylon. We assess the quality of all components through extensive material characterization, discuss their potential for sustainable recycling, and provide a techno-economic analysis of the economic feasibility of the process.

Science & Technology - Other Topics↗
DOE OSTI2026

Hydrogenolysis Versus Hydrocracking for Polyolefin Upcycling

Global plastic production has reached 413.8 million metric tons in 2024 and is forecasted to surpass 1.2 billion metric tons by 2050. Polyolefins, mainly polyethylene (PE) and polypropylene (PP), dominate single-use packaging and account for approximately 55% of global plastic waste. The chemical inertness that makes these materials desirable for commercial applications also renders them persistent in the environment. Current recycling technologies have proven to be insufficient to divert plastic waste from landfills or environmental loss due to technical limitations and poor economic incentives. Conventional mechanical recycling is a form of downcycling, in which the polymer remelting process results in products with inferior material properties and reduced market value. Pyrolysis, a thermochemical route used for the chemical recycling of plastic wastes into refinery feedstock, requires severe conditions, typically 400–600 °C in an oxygen-free environment. The high temperature drives up energy costs and produces a wide range of poorly defined products, including undesirable light gases and heavy tars that pose challenges for downstream processing. As an alternative, catalytic chemical recycling offers a promising route for converting waste polyolefins back into value-added hydrocarbons—such as fuels, lubricant base oils, and other chemical feedstocks—at temperatures typically below 300 °C. This opinion article focuses on two dominant pathways in heterogeneous catalysis that are used to cleave the C–C bonds of polyolefins: hydrogenolysis and hydrocracking. Both catalytic pathways have the potential to selectively convert polyolefin waste into valuable fuels and chemical feedstocks under mild conditions. Notably, while hydrocracking primarily yields branched hydrocarbon products, hydrogenolysis predominantly produces linear hydrocarbons. Here, we compare the mechanisms and catalyst designs for hydrocracking and hydrogenolysis, analyze critical technical challenges from catalyst stability to process engineering, and provide an outlook on how these complementary pathways can be used to repurpose plastic waste into valuable products.

Zhang, Ruoxi [Iowa State Univ., Ames, IA (United S↗
DOE OSTI2024

Plastic Parallel Pathways Platform- 4P Model

The U.S. generates 42 million metric tons of plastic waste each year - the most of any country - of which less than 9% is recycled. This represents an estimated loss of $2.3 billion and 3.4 EJ embodied energy per year. Plastic use reduction, reuse and recycling are thus increasingly important, but making informed policy and research decisions within this space can be challenging given the diverse range of available solutions. Various recycling and waste management options are available for plastics, such as conversion into energy (incineration, pyrolysis, gasification), conversion to lower- or higher-grade plastics (mechanical recycling, chemical or enzymatic depolymerization processes, dissolution) or up-cycling to feedstock chemicals (photo/electro/catalytic methods, pyrolysis, gasification). While many previous publications have investigated a subset of these options, there is currently no modelling platform that can quantitatively assess and compare the economic and environmental impacts of all these different plastic management pathways and their respective products simultaneously. To directly compare the benefits and disadvantages of plastic-to-x technologies, we propose a novel analysis framework: the Plastic Parallel Pathways Platform (4P). 4P will model a systems analysis framework for capturing plastic material flows processed via different waste management scenarios. The total economic cost and greenhouse gas emissions (as well as additional economic, energetic, and environmental metrics indicators) of a given scenario will be calculated enabling comparison to other scenarios, thereby informing decisions on plastic recycling pathways.

circular economy↗
DOE OSTI2026

Polyolefin blends with co-continuous architectures enabled by dynamic covalent crosslinking

Blending polymers produces brittle materials due to macrophase separation and poor interfacial adhesion, which is exemplified by mixtures of polyolefins. This presents a formidable challenge for the mechanical recycling of mixed plastic waste. Here, we demonstrate that dynamic covalent crosslinking of immiscible polyolefin blends creates macrophase separated co-continuous architectures, yet they display excellent mechanical properties, which challenges the conventional wisdom regarding morphology-property relationships in polymer blend compatibilization. We find that the position and orientation of dynamic crosslinks and their influence on crystallinity are key to understanding the structure-morphology-property relationships. In particular, high-resolution microscopy imaging reveals alignment of crystallite planes with strong orientational preference, particularly at polymer-polymer interfaces, which contribute to material performance. We further demonstrate that changes in crosslinker density and valency allow the properties of binary and ternary polyolefin blends to be tuned in a modular fashion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

PET waste- and bio-derived imine vitrimers for shape-memory, intrinsic flame-retardant, and recyclable carbon fiber composites

Developing circular multifunctional vitrimers and carbon fiber–reinforced polymers (CFRPs) that are simultaneously recyclable, mechanically robust, and intrinsically flame retardant remains a major challenge. Here, in this study, we report multifunctional vitrimers and their carbon fiber–reinforced vitrimer (CFRV) composites, where the vitrimer design integrates closed-loop recyclability, enhanced interfacial adhesion, and intrinsic flame retardancy within a single materials platform. The vitrimer matrix is synthesized from post-consumer polyethylene terephthalate (PET) waste and a vanillin-derived phosphorus-containing crosslinker, forming an imine-based network. The resulting vitrimer resin exhibits high tensile strength, thermal healability, repeated reprocessability, programmable shape memory, and rapid chemical depolymerization under mild conditions. Amine-functionalized carbon fibers significantly improve fiber–matrix interfacial bonding, yielding CFRVs with tensile strengths up to 789 MPa and complete recovery of structurally intact fibers after chemical recycling. The phosphorus-rich aromatic network further imparts intrinsic flame retardancy, enabling self-extinguishing behavior without external additives. This work advances a materials design paradigm for next-generation multifunctional, sustainable vitrimers and CFRVs, while simultaneously addressing the recycling challenges associated with both plastic and CFRP waste.

Bio-derived crosslinker↗
DOE OSTI2023

Benefits and Risks of New Polymers in the Current and Future Recycling System

New plastics are increasingly being developed to address challenges around plastic pollution and end-of-life management. However, the incorporation of these new polymers into the existing plastic ecosystem raises numerous risks, as well as some benefits. This flash talk briefly discusses how new plastics could raise contamination levels and prevent mechanical recycling, how we could mitigate that risk by improving education around recycling collection, and how new plastics could potentially reduce the cost and environmental impact of certain chemical recycling technologies.

benefit-risk analysis↗
DOE OSTI2023

Endowing Polythioester Vitrimer with Intrinsic Crystallinity and Chemical Recyclability

Abstract Technologically important thermosets face a long‐standing end‐of‐life (EoL) problem of non‐reprocessability, a more sustainable solution of which has resolved to nascent vitrimers that can merge the robust material properties of thermosets and the reprocessability of thermoplastics. However, the lifecycle of vitrimers is still finite, as they often suffer from significant deterioration of mechanical performance following multiple reprocessing cycles, analogous to mechanical recycling, and they often show undesired creep under working conditions. To address these two key limitations, we have developed a cross‐linked semi‐crystalline polythioester with both dynamic covalent bonds and intrinsic crystallinity and chemical recyclability, affording a vitrimeric system that exhibits not only reprocessability and crystallinity‐restricted creep but also complete chemical recyclability to initial monomer by catalyzed depolymerization in solution or bulk. Therefore, reported herein is an “infinite” vitrimer system that is empowered with a facile closed‐loop EoL option once serial reprocessing deteriorates performance and the material can no longer meet the application requirements. Specifically, the polythioester vitrimer was constructed by copolymerization of a bicyclic thioester with a bis‐dithiolane, producing dynamically cross‐linked polythioesters with excellent property tunability, from amorphous to semi‐crystalline states and melting transition temperatures from 91 to 178 °C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Biological Upcycling of Plastics Waste

Plastic wastes accumulate in the environment, impacting wildlife and human health and representing a significant pool of inexpensive waste carbon that could form feedstock for the sustainable production of commodity chemicals, monomers, and specialty chemicals. Current mechanical recycling technologies are not economically attractive due to the lower-quality plastics that are produced in each iteration. Thus, the development of a plastics economy requires a solution that can deconstruct plastics and generate value from the deconstruction products. Biological systems can provide such value by allowing for the processing of mixed plastics waste streams via enzymatic specificity and using engineered metabolic pathways to produce upcycling targets. We focus on the use of biological systems for waste plastics deconstruction and upcycling. We highlight documented and predicted mechanisms through which plastics are biologically deconstructed and assimilated and provide examples of upcycled products from biological systems. Additionally, we detail current challenges in the field, including the discovery and development of microorganisms and enzymes for deconstructing non–polyethylene terephthalate plastics, the selection of appropriate target molecules to incentivize development of a plastic bioeconomy, and the selection of microbial chassis for the valorization of deconstruction products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Plastic Parallel Pathways Platform - 4P Model

Global momentum is building towards a circular economy capable of keeping plastics in use and out of waste streams. Given that 79% of all plastic produced since 1950 has accumulated in landfills or the natural environment,rapid implementation of various end-of-life (EoL) management technologies will be needed to reach this target. However, it can be challenging to develop an effective plastic EoL strategy when the available options - chemical or molecular recycling, energy recovery, upcycling, downcycling, closed-loop (plastic-to-plastic) or open-loop (plastic-to-x) recycling, among others - can generate products ranging from low-grade to virgin-quality plastic and from fuels to value-added chemicals. We present a flexible material flow model capable of analyzing the effects of both plastic-to-plastic and plastic-to-x EoL management strategies on the U.S. PET economy. This Plastic Parallel Pathways Platform (4P) assesses the environmental impacts, costs, and circularity of a PET system in which waste is managed through six potential EoL pathways: landfill, incineration with energy recovery, pyrolysis to fuel oil, upcycling to glass fiber reinforced plastic (GFRP), mechanical recycling to low-grade PET, and chemical recycling (glycolysis) to bottle-grade PET. We compare the pathways across multiple metrics using multi-criteria decision analysis (MCDA) and then use a brute force algorithm to predict an optimal combination of EoL pathways to minimize greenhouse gas (GHG) emissions and costs and maximize circularity. This work highlights the need to implement a diverse portfolio of EoL strategies in parallel to enable a PET economy that meets environmental, economic, and circularity requirements simultaneously.

downcycling↗
DOE OSTI2024

Catalytic Upcycling of Polyolefins

The large production volumes of commodity polyolefins (specifically, polyethylene, polypropylene, polystyrene, and poly(vinyl chloride)), in conjunction with their low unit values and multitude of short-term uses, have resulted in a significant and pressing waste management challenge. Only a small fraction of these polyolefins is currently mechanically recycled, with the rest being incinerated, accumulating in landfills, or leaking into the natural environment. Since polyolefins are energy-rich materials, there is considerable interest in recouping some of their chemical value while simultaneously motivating more responsible end-of-life management. An emerging strategy is catalytic depolymerization, in which a portion of the C–C bonds in the polyolefin backbone is broken with the assistance of a catalyst and, in some cases, additional small molecule reagents. When the products are small molecules or materials with higher value in their own right, or as chemical feedstocks, the process is called upcycling. This review summarizes recent progress for four major catalytic upcycling strategies: hydrogenolysis, (hydro)cracking, tandem processes involving metathesis, and selective oxidation. Key considerations include macromolecular reaction mechanisms relative to small molecule mechanisms, catalyst design for macromolecular transformations, and the effect of process conditions on product selectivity. Metrics for describing polyolefin upcycling are critically evaluated, and an outlook for future advances is described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Understanding Depolymerization and Repolymerization Toward Repurposing Polymer Waste Into Valuable Chemicals & Materials

The versatility of synthetic polymers has led to their continual and escalating production that has accompanied mismanagement at their end-of-life. Exploring and understanding complementary avenues to repurpose plastic waste beyond traditional mechanical recycling can unlock new opportunities in providing feedstock flexibility, securing supply chains, recovering valuable materials, and enabling new valorization paths. Chemical recycling allows for the return to monomers, tailored oligomers, and polymers, even from mixed states of post-consumer waste plastics. This review article summarizes our research team's efforts on elucidating key insights surrounding plastic depolymerization and repolymerization into valorized products. We revealed organocatalyst design rules lead to highly effective and selective deconstruction of condensation polymers. The intricacies of tailoring the reaction environment to produce products of specific lengths and desired functionalities transform low-value waste feedstocks into high-performance materials with embedded circularity. Other types of polymers, including polyolefins and polyakenamers, have also been designed and converted into valuable products. There remain opportunities for further developments such as low-energy and precision depolymerization, adoption of cutting-edge small molecule transformation to access functionalized polymer scaffolds typically inaccessible otherwise, as well as precision design and understanding through the aid of advanced tools.

Galan, Nick [ORNL]↗
DOE OSTI2023

Comparing Parallel Plastic‐to‐X Pathways and Their Role in a Circular Economy for PET Bottles

Abstract The United States generates the most plastic waste of any country and is a top contributor to global plastic pollution. Multiple end‐of‐life strategies must be implemented to minimize environmental impacts and retain valuable plastic material, but it is challenging to compare options that generate products with different lifetimes and utilities. Herein, they present a material flow model equipped with consequential life cycle assessment, cost analysis, and a plastic circularity indicator that considers product quality and lifetime. The model is used to estimate the greenhouse gas (GHG) emissions, circularity, and cost of polyethylene terephthalate (PET) bottle mechanical downcycling to lower‐quality resin, closed‐loop glycolysis to food‐grade PET, upcycling to glass fiber‐reinforced plastic, and conversion to non‐plastic products (electricity, oil) on a United States economy‐wide basis for the year 2020. A brute force algorithm suggests that a combination of 68% glycolysis, 11% mechanical recycling, 6% upcycling, 9% landfilling, and 5% incineration can minimize the cost and GHG emissions and maximize the circularity of the current PET economy. However, uncertainty around transportation distances, materials recovery facility efficiencies, and recycling yields can result in different “optimal” pathway mixes. This flexible framework enables informed decision‐making to move toward a cost‐ and environment‐conscious circular economy for plastic.

09 BIOMASS FUELS↗
DOE OSTI2023

Toughening Brittle Bio‐P3HB with Synthetic P3HB of Engineered Stereomicrostructures

Abstract Poly(3‐hydroxybutyrate) (P3HB), a biologically produced, biodegradable natural polyester, exhibits excellent thermal and barrier properties but suffers from mechanical brittleness, largely limiting its applications. Here we report a mono‐material product design strategy to toughen stereoperfect, brittle bio or synthetic P3HB by blending it with stereomicrostructurally engineered P3HB. Through tacticity ([ mm ] from 0 to 100 %) and molecular weight ( M n to 788 kDa) tuning, high‐performance synthetic P3HB materials with tensile strength to ≈30 MPa, fracture strain to ≈800 %, and toughness to 126 MJ m −3 (>110× tougher than bio‐P3HB) have been produced. Physical blending of the brittle P3HB with such P3HB in 10 to 90 wt % dramatically enhances its ductility from ≈5 % to 95–450 % and optical clarity from 19 % to 85 % visible light transmittance while maintaining desirably high elastic modulus (>1 GPa), tensile strength (>35 MPa), and melting temperature (160–170 °C). This P3HB‐toughening‐P3HB methodology departs from the traditional approach of incorporating chemically distinct components to toughen P3HB, which hinders chemical or mechanical recycling, highlighting the potential of the mono‐material product design solely based on biodegradable P3HB to deliver P3HB materials with diverse performance properties.

Zhang, Zhen↗
DOE OSTI2023

Toughening Brittle Bio‐P3HB with Synthetic P3HB of Engineered Stereomicrostructures

Abstract Poly(3‐hydroxybutyrate) (P3HB), a biologically produced, biodegradable natural polyester, exhibits excellent thermal and barrier properties but suffers from mechanical brittleness, largely limiting its applications. Here we report a mono‐material product design strategy to toughen stereoperfect, brittle bio or synthetic P3HB by blending it with stereomicrostructurally engineered P3HB. Through tacticity ([ mm ] from 0 to 100 %) and molecular weight ( M n to 788 kDa) tuning, high‐performance synthetic P3HB materials with tensile strength to ≈30 MPa, fracture strain to ≈800 %, and toughness to 126 MJ m −3 (>110× tougher than bio‐P3HB) have been produced. Physical blending of the brittle P3HB with such P3HB in 10 to 90 wt % dramatically enhances its ductility from ≈5 % to 95–450 % and optical clarity from 19 % to 85 % visible light transmittance while maintaining desirably high elastic modulus (>1 GPa), tensile strength (>35 MPa), and melting temperature (160–170 °C). This P3HB‐toughening‐P3HB methodology departs from the traditional approach of incorporating chemically distinct components to toughen P3HB, which hinders chemical or mechanical recycling, highlighting the potential of the mono‐material product design solely based on biodegradable P3HB to deliver P3HB materials with diverse performance properties.

Chemistry↗
DOE OSTI2025

Investigating the Role of Acid Sites in the Hydrocracking of Polyethylene-EVOH Multilayer Film Waste over Pt/BEA Catalyst

Multilayer polymer films (MFs) containing poly(ethylene-co-vinyl alcohol) (EVOH) and polyolefins are ubiquitous in single-use food and medical packaging. MFs are currently landfilled or incinerated rather than mechanically recycled because of the processing difficulties associated with their form factor and complex multicomponent structures. Advanced chemical recycling is a promising solution. Prior reports have explored hydrogenolysis and hydrodeoxygenation to convert EVOH, but these technologies are limited by catalyst deactivation and slow apparent kinetics, respectively. Alternatively, in this work, we demonstrate the efficient hydrocracking of commercial MFs into naphtha range (C5-C12) alkanes over platinum (Pt) supported on acidic zeolites. Mixtures of low-density polyethylene (LDPE) and EVOH are utilized as MF surrogates to gain fundamental insights. Pt deposited on BEA supports with varying Lewis acid site (LAS) concentrations are synthesized and tested for hydrocracking. Surprisingly, Pt/BEA with high LAS concentrations demonstrate improved activity for LPDE/EVOH blends over LDPE alone. In contrast, LAS concentrations are shown to have no influence on LDPE hydrocracking. LAS and Brønsted acid sites (BAS) catalyze the dehydration of EVOH to form water, which improves LDPE hydrocracking. Polyaromatics formed primarily via EVOH thermal degradation lead to detrimental coke formation, which hinders hydrocracking activity. Reaction conditions and feed ratios of LDPE and EVOH are tuned to balance these competing effects. Reusability tests demonstrate that Pt/BEA maintains high activity (81% conversion in 2 h) and high selectivity towards naphtha (78%) over multiple reuse cycles. Furthermore, these findings position hydrocracking as a promising technology for the circularity of complex MF plastic waste.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A pulsed current-mode class-D low-voltage high-bandwidth power amplifier for portable NMR systems

Low-field NMR has seen growing interest in recent years, especially for portable applications. The lower homogeneity magnets used for portable applications require short RF pulses to ensure enough transmit bandwidth to excite the sample volume and also support short echo periods. Furthermore, the preferred use of a high-Q coil to improve signal-to-noise ratio (SNR) prolongs the pulse transients. Thus, at such low Larmor frequencies, the excitation pulse transients become comparable or longer than the pulse length, such that the transmit bandwidth begins to limit measurement SNR. This paper describes the design of a pulsed current-mode class-D power (PCMCD) transmitter that addresses this issue by generating high power in a tuned sample coil while maintaining short transients, thus resulting in high output bandwidth. The transmitter also uses a charge recycling mechanism to maximize power efficiency for RF train excitation, which also results in faster pulse repetition rate and reduces allowable echo time. In this work, experimental results from a small form-factor PCMCD transmitter are presented. This design generates a peak RF power of 240 W into a 9.16 µH coil at 4 MHz while operating off a single 12 V power supply. NMR measurement results using the transmitter are also described, showing minimum achievable echo time of 70 µs and 25 µs depending on the transmitter mode of operation.

47 OTHER INSTRUMENTATION↗