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Effects of PLA/PHB Blend Ratio and Wood Flour Loading on the Melt Rheology and Thermomechanical Properties of Biobased Polymer Composites

The development of sustainable, biobased polymer composites is crucial for reducing supply chain dependence on fossil fuels. A major challenge lies in understanding and predicting the processability of these sustainable material alternatives, which directly impacts large-scale manufacturing. Here, this study systematically investigates the effect of poly(lactic acid) (PLA)/polyhydroxybutyrate (PHB) blend ratios and wood flour (WF) loadings on the thermal, rheological, and mechanical properties of the composites. Composites were prepared via melt compounding and characterized by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), oscillatory shear melt rheology, tensile testing, and scanning electron microscopy. Results showed that increasing the PHB content lowered the glass transition temperature, while higher PHB and WF loadings decreased thermal stability. Complex viscosity decreased with increasing PHB in 0 and 10% WF, whereas it increased in 20% and 30% WF for PHB-rich blends (80/20 and 70/30 PLA/PHB) due to stronger filler interactions with flexible PHB chains. At 30% WF, PHB-containing composites also showed elastic dominance with G′ higher than G″. This behavior was confirmed by van Gurp–Palmen plots, where the phase angle decreased with increasing PHB and WF loadings. WF addition also shifted Cole–Cole plots away from semicircular terminal relaxation, while time–temperature superposition validity was maintained, confirming that polymer chain dynamics continue to dominate melt behavior. Young’s modulus increased with WF loading, while tensile strength and toughness decreased due to weaker interfacial adhesion between the matrix and the filler. Interestingly, 10% WF systems containing PHB exhibited the highest toughness among all of the filled systems, indicating synergistic reinforcement from WF fillers and PHB-induced ductility. Overall, melt rheology effectively captured the internal structure and stiffness of the composites as the formulation changed, reinforcing the concept that the PLA/PHB ratio and WF content can be tuned to adjust melt elasticity and balance mechanical property trade-offs for targeted applications.

melt rheology

Biobased Poly(dodecylene Furanoate) with Inherent Advantages in Performance and Circularity

Biobased polymers are gaining traction toward more sustainable flexible-film packaging, yet overcoming trade-offs between their performance properties and end-of-life (EoL) options still remains a challenge. Here, it is shown that biobased poly(dodecylene 2,5-furanoate) (PDDF), synthesized via both step-growth polycondensation and chain-growth ring-opening polymerization methods, exhibits advantages not only in gas barrier properties but also in EoL options due to its biodegradability and closed-loop chemical circularity. Specifically, PDDF displays significantly lower oxygen and carbon dioxide permeability than commercial poly(butylene adipate-co-terephthalate) (PBAT) and linear low-density polyethylene , alongside a markedly higher modulus (by ≈3 ×) and reduced water vapor transmission rate compared to PBAT. This superior performance is attributed to the inherently rigid, polar, H-bonding furan rings that enhance chain interaction, packing and crystallinity and thus reduce free volume impeding gas diffusion, while the long hydrophobic dodecylene segments inhibit water permeation. Furthermore, PDDF can be recycled back to its cyclic monomer by base-catalyzed depolymerization or diester and diol monomers by simple methanolysis. These superior barrier properties, coupled with biodegradation and closed-loop circularity, highlight the potential of the biobased PDDF as a more sustainable alternative for packaging.

Poly(dodecylene 2,5-furanoate) (PDDF)

Designing a Block Copolymer Membrane for Selective Transport of Lactic Acid from Aqueous Mixtures

We report the design and synthesis of a triblock copolymer-based membrane for enabling selective transport of lactic acid from aqueous solutions. This is relevant to the production of polylactic acid, one of the few biodegradable and biobased polymers with sufficient mechanical strength for practical applications. The end blocks are positively charged with negatively charged lactate counterions. The middle block is polybutadiene (PBD). Due to microphase separation, the charged blocks form channels for transporting lactic acid. The mechanical integrity of the membrane is controlled by cross-linking the PBD block. Transport of lactic acid and water across the membrane was studied by placing the membrane between two chambers, a feed chamber containing aqueous lactic acid solutions, and a receiving chamber containing pure water. The lactic acid concentration in the receiving chamber was monitored as a function of time using conductivity, HPLC, and NMR. The corresponding flux of water from the receiving chamber to the feed chamber was measured using an NMR-based approach. The lactic acid and water permeabilities through our membrane were (1.12 ± 0.05) × 10–8 and (8.58 ± 0.75) × 10–9 cm2 s–1. To our knowledge, there are no reports of lactic acid permeabilities through any membrane in the literature. The separation factor of our membrane, αLA/water, 1.305 ± 0.123, is comparable to that of membranes used for selective transport of ethanol, despite the fact that lactic acid is a much larger molecule than ethanol. Selective transport of lactic acid in our membrane is governed mainly by differences in solubility; lactic acid is 18 times more soluble in the membrane than water.

Jana, Rounak

Lignin-Derived Methoxyterephthalates for Performance-Advantaged Polymers and Plasticizers

Lignin-derived aromatic carboxylic acids can be produced from oxidative catalytic processes and are promising building blocks for performance-advantaged bioproducts that leverage their inherent heteroatom functionalities. Here, we synthesize 2-methoxyterephthalate and 2,6-dimethoxyterephthalate derivatives by electrochemical carboxylation of guaiacyl- and syringyl-derived lignin monomers obtained from the oxidative deconstruction of lignin. These methoxylated terephthalates are evaluated as comonomers in poly(ethylene terephthalate) (PET) and as plasticizers that could replace petrochemically-derived isophthalate and phthalate, respectively. Specifically, we copolymerize 2-methoxy- and 2,6-dimethoxyterephthalate with dimethyl terephthalate to form several PET copolymers, both of which enable the properties of PET to be tuned, with an incorporation beyond 25% producing amorphous polyesters. At 10 mol % loading in the copolymers, we demonstrate that the bioderived comonomers exhibit comparable behavior to isophthalic acid, a commonly used comonomer in PET, by lowering the crystallinity and melting temperature. Moreover, methoxyterephthalate esters (2-ethylhexyl and butyl) are compared to phthalate and terephthalate ester counterparts used as poly(vinyl chloride) (PVC) plasticizers. The bioderived plasticizers are comparable to the petroleum-derived incumbents in reducing the glass transition temperature and increasing the thermal stability of PVC. Furthermore, the dimethoxyterephthalic esters are expected to have an extended lifetime in the polymer matrix due to their lower volatility and lower diffusion coefficients calculated by molecular dynamic simulations. These results demonstrate that the isophthalate and phthalate components in polyesters and plasticizers, respectively, could be substituted with biobased methoxyterephthalate derivatives.

09 BIOMASS FUELS

Designing Recyclable Biomass-Based Polyesters (Final Technical Report)

This project successfully demonstrated the production of sustainable polyesters from biomass-derived monomers, offering properties on par with or superior to fossil-based plastics such as LLDPE and PBAT. Using renewable chemical platforms like furfural and HMF, we synthesized over eight novel monomers and nearly 100 aliphatic-aromatic polyesters. Among these, PPeAT and PDDF emerged as highly promising candidates for flexible packaging applications, exhibiting excellent mechanical performance, tunable thermal properties, and enhanced barrier characteristics. Key advances included the development of ring-opening polymerization strategies using cyclic monomer intermediates to produce high molecular weight materials with excellent control. The resulting polymers achieved biobased content of at least 44 wt.%. We also implemented chemical recycling via catalytic methanolysis, recovering over 90% of monomers from PPeAT at semi-pilot scale. This supports a circular economy approach by enabling material reuse without performance loss. Techno-economic and life cycle assessments confirmed that these polyesters can reduce greenhouse gas emissions by up to 50% compared to petroleum-derived alternatives. Favorable mechanical properties may further reduce material demand, and cost competitiveness was demonstrated under specific market conditions. Feedstock cost and environmental footprint were identified as primary levers for future optimization. In summary, the project met or closely approached all technical targets, including biodegradability, strength, and processing compatibility. While minor issues such as color and melting point variation remain, the results strongly support continued development and scale-up of these sustainable materials.

09 BIOMASS FUELS

Force-Triggered, Biobased Sealants for Prefabricated Building Components: Toward Improved Efficiency and Performance

The prefabricated building construction industry has made extensive progress in expediting the manufacture of prefabricated components at off-site plants. However, the sealing of joints between these components, which is crucial to ensuring the weatherproofing of the assembly, still represents a labor-intensive, on-site effort that relies on the manual installation of tapes and caulks. Here, to reduce work at the jobsite and improve the airtightness and waterproofness of building envelopes, we developed a sealant that can be installed at the plant on prefab components and have the curing reaction triggered at the jobsite by using microencapsulation technology to separate the reactive agents. A series of force-triggered, high-strength, and fast-curing sealants derived from biobased feedstocks were developed, which consist of a biobased epoxy agent encapsulated in a polymer shell, embedded in a biobased amine curing agent. The shell of the microcapsules allows an effective separation of the reactive species in the one-part sealant, allowing shelf stability to an otherwise fast-curing system as well as improving the hydrophobicity of the whole system. When force activates and breaks the microcapsules, the highly reactive epoxy and amine mix and cure, exhibiting peel strength values of up to 143 ppi (pounds per inch). The hydrophobicity of the sealants allows them to retain up to 94% of the original peel strength after complete submersion in water for 24 h, showcasing the water resistivity of the sealant system. The open-air shelf stability of the sealant complex is demonstrated by the obtention of peel strength values of ∼16 ppi when triggering the curing reaction even after being exposed 8 months to open air and humidity. The successful on-demand triggering of curing reactions and the shelf stability provide efficacy of these force-triggered sealants for installation on prefabricated components, storage for months prior to delivery, and assembly at a jobsite. These force-triggered biobased sealants for prefabricated buildings can result in lower installation time and cost and better performance than tapes and caulks at the jobsite.

biobased

Closed‐Loop Recycling of Poly(pentylene Adipate‐ co ‐Terephthalate) via Amine‐Catalyzed Methanolysis

Advancing circularity through effective chemical recycling strategies is essential for enabling the sustainable use of emerging biodegradable polyesters in film applications. In this context, poly(pentylene adipate-co-terephthalate) with a 40/60 adipate-to-terephthalate ratio (PPeAT60), a significantly stiffer and partially biobased copolyester recently reported by our team, offers improved mechanical performance and processability compared to commercial poly(butylene adipate-co-terephthalate), while providing a platform to evaluate advanced recycling approaches for film applications. Here, this study describes depolymerization of PPeAT60 through amine-catalyzed methanolysis, followed by the repolymerization of the recovered monomers. The resulting repolymerized material exhibited a molar mass distribution, chemical structure, and thermal stability comparable to the virgin polymer, confirming the technical feasibility of the methanolysis-based recycling route. Both polymers displayed nearly identical melting, glass transition, and decomposition temperatures, crystallinity, and modulus, demonstrating full structural and mechanical reproducibility after recycling. Variations in crystallization kinetics, elongation at break, and barrier properties likely arise from trace impurities (<1%) introduced during processing acting as nucleating and stress-inducing agents. Overall, these results demonstrate that PPeAT60 retains its key properties after chemical recycling, establishing methanolysis as a promising platform for recycling of this partially biobased polymer that may be able to replace both conventional polyolefins and PBAT in flexible packaging applications.

09 BIOMASS FUELS

Tunable and Degradable Dynamic Thermosets from Compatibilized Polyhydroxyalkanoate Blends

Polyhydroxyalkanoates (PHAs) are versatile, biobased polyesters that are often targeted for use as degradable thermoplastic replacements for polyolefins. Given the substantial chemical diversity of PHA, their potential as cross-linked polymers could also enable similar platforms for reversible, degradable thermosets. In this work, we genetically engineered Pseudomonas putida KT2440 to synthesize poly(3-hydroxybutyrate-co-3-hydroxyundecenoate) (PHBU), which contains both 3-hydroxybutyrate and unsaturated 3-hydroxyundecenoate components. To reduce the brittleness of this polymer, we physically blended PHBU with the soft copolymer poly(3-hydroxydecanonate-co-3-hydroxyundecenoate) in mass ratios of 1:3, 1:1, and 3:1. Upon observing varying degrees of immiscibility by scanning electron microscopy, we installed dynamic boronic ester cross-links via thiol–ene click chemistry, which resulted in compatibilized dynamic thermoset blends ranging in hard, medium, and soft rubber or elastomer thermomechanical profiles. These dynamic thermoset blends were subjected to controlled biological degradation experiments in freshwater conditions, achieving timely mass loss despite the cross-linked architectures. Overall, this work highlights a two-component platform for the production of degradable and reprocessable dynamic thermoset blends suitable for several classes of cross-linked polymer technologies from tailored, biological PHA copolymers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH

Enabling Partnership between South Carolina and NREL for Advancing Opportunities in Plastics Recycling Research (EPSCOR for Plastics Recycling)

Proposal Objectives: 1. Utilize depolymerization/fractionation techniques to recover highly processable and reactive feedstocks for polymer synthesis from lignin. 2. Synthesize lignin‐derived non‐isocyanate polyurethane, epoxy, and polyamide using non‐ toxic, biobased route designed for chemical recycling. Characterize resulting materials. 3. Design a high‐yielding chemical recycling process for as‐synthesized materials yielding usable building blocks for many generations of polymer synthesis. 4. Optimize chemical recycling of PET waste for the synthesis of lignin‐based polymers. Compare properties to commercial materials. 5. Optimize reaction conditions and recycling steps to facilitate enhanced sustainability of the synthetic steps and final properties of materials. 6. Complete a lifecycle assessment of lignin utilization and chemical recycling to compare their environmental performance to that of materials produced from virgin material. Identify hot spots and benefits using the chemical recycling process.

36 MATERIALS SCIENCE

Biobased chemical recycling: aminolysis of PET using renewable reagents and monomers to synthesize new semi-aromatic polyamides

Chemical recycling of PET is a method of depolymerizing polymer chains to monomeric components enabling the synthesis of second-generation materials with virgin-like quality. Commercial chemical recycling techniques rely upon high pressure methanolysis to create precursors capable of synthesizing a second-generation PET resin. However, despite the circular approach of methanolysis, a product with a very short lifespan and similar value is created. The approach of the current study is to utilize aminolysis as an ambient pressure technique to create precursors for higher value materials with longer lifespans to address the current crisis in plastic waste. Semi-aromatic polyamides (SAP) are desired in this circumstance because of their high melting point and heat resistance combined with good melt-processability similar to aliphatic polyamides. In this study SAPs were synthesized using precursors recovered from the aminolysis of PET employing biobased diamines and dicarboxylic acids. While aminolysis has been explored in previous studies, this work investigated the use of biobased components from castor oil: decamethylene diamine during recycling and sebacic acid during polymerization. Polymer synthesis resulted in the formation of SAPs similar to polyphthalamides (PPA) with novel structures given the aromatic portion from terephthalic acid (TPA) and aliphatic portion from the diamines and diacids. The synthesized materials exhibited excellent thermal stability with high glass transition temperatures. Novel polymers were created with varying aliphatic chain length to understand fundamental parameters needed to produce a valuable polymer from post-consumer waste.

High performance Applications

Understanding and Mitigating Stickiness in Biochar Produced through Acid Hydrolysis and Dehydration

Levulinic acid is a platform chemical with significant potential for conversion into a wide range of biobased chemicals and fuels. A common process for producing levulinic acid from lignocellulosic feedstocks involves acid hydrolysis and dehydration (AHDH), where hexose polymers are hydrolyzed into monomeric sugars and subsequently dehydrated to levulinic acid and formic acid in the presence of dilute sulfuric acid. However, scaling the AHDH process is challenging because of the formation of byproducts such as sticky biochar, which accumulates in continuous-flow reactors, reducing effective reaction volume and increasing process downtime. This study investigates the effect of a chemical preconditioning step on mitigating sticky biochar formation. Woody biomass was preconditioned at 170 °C with 0.26 wt % sulfuric acid for 30 min, resulting in substantial removal of hemicellulose and acid-soluble lignin. AHDH of these preconditioned solids produced biochar that did not adhere to reactor surfaces. TGA analysis confirmed that the chemical preconditioning step minimized interactions between hemicellulose-derived degradation products and lignin side chains, reducing sticky char formation. Additionally, the study observed a 6% higher yield of organic acids from softwood species compared to hardwoods, with bark content shown to negatively impact yield. These findings suggest that targeted preconditioning of lignocellulosic biomass can enhance reactor operability and improve organic acid production efficiency in AHDH processes.

biopolymers

Biodegradable Biocomposite Development for Large Scale Additive Manufacturing

Oak Ridge National Laboratory (ORNL) worked with Mitsubishi Chemical America, Inc. to develop a highly biodegradable ~100% biobased feedstock for large format additive manufacturing (AM). Together, they developed a AM feedstock based on the biobased polyester, polybutylene succinate (PBS), that is typically used in agriculture and packaging projects. The motivation for this work was to leverage the high degradability of this polymer in AM to create a new avenue for end-of-life disposal of the product. A composite feedstock was developed from PBS, polylactic acid (PLA), and wood flour (WF). While WF improves printability, reduces feedstock cost, and can improve stiffness, it also often results in a loss in tensile strength which can inhibit/limit application of the material. To recover the loss in tensile strength suffered by including large quantities, up to 30 wt%, WF in the composite a chain extender was used to compatibilze the different composite constituents with each other. The feedstock was used to 3D-print demonstration mold for precast concrete catch basins and was tested by casting 750 lbs of concrete. The mold survived the demonstration. Aerobic degradation testing of the composite feedstock showed that it was highly degradable, 40% biodegradation after 90 days, compared to other incumbent biobased feedstocks.

36 MATERIALS SCIENCE

Biodegradable Biocomposite Development for Large Scale Additive Manufacturing

Oak Ridge National Laboratory (ORNL) worked with Mitsubishi Chemical America, Inc. to develop a highly biodegradable ~100% biobased feedstock for large format additive manufacturing (AM). Together, they developed an AM feedstock based on the biobased polyester, polybutylene succinate (PBS), that is typically used in agriculture and packaging projects. The motivation for this work was to leverage the high degradability of this polymer in AM to create a new avenue for end-of-life disposal of the product. A composite feedstock was developed from PBS, polylactic acid (PLA), and wood flour (WF). While WF improves printability, reduces feedstock cost, and can improve stiffness, it also often results in a loss in tensile strength which can inhibit/limit applications of the material. To recover the loss in tensile strength suffered by including large quantities, up to 30 wt.% WF in the composite, a chain extender was used to compatibilize the different composite constituents with each other. The feedstock was used to 3D-print a demonstration mold for precast concrete catch basins and was tested by casting 750 lbs of concrete. The mold survived the demonstration. Aerobic degradation testing of the composite feedstock showed that it was highly degradable, 40% biodegradation after 90 days, compared to other incumbent biobased feedstocks.

100% biobased feedstock for large format additive

Recent Advances in the Use of Ionic Liquids and Deep Eutectic Solvents for Lignocellulosic Biorefineries and Biobased Chemical and Material Production

Biorefineries, which process biomass feedstocks into valuable (bio)products, aim to replace fossil fuel-based refineries to produce energy and chemicals, reducing environmental and health hazards, including climate change, and supporting a sustainable economy. In particular, lignocellulose-based biorefineries, utilizing the most abundant renewable feedstock on Earth, have significant potential to supply sustainable energy, chemicals and materials. Ionic liquids (ILs, organic salts with low melting temperatures) and deep eutectic solvents (DESs, mixtures with eutectic points lower than the ideal mixture) are capable of dissolving some of the key lignocellulose polymers, and even the whole biomass. Furthermore, they have intrinsic advantages over molecular solvents, including safer usage profiles and high tunability, which allow tailored physicochemical properties. Such properties provide unique opportunities for the development of new processes that could unlock the full potential of future biorefineries. Here, we review the current state of lignocellulosic biomass processing with ILs and DESs, with a specific focus on the pretreatment chemistry, process flow and products from each component; followed by discussions on sustainability assessments and technological challenges. We aim to inform the research community about the opportunities, challenges and perspectives in developing truly sustainable lignocellulose-based biorefineries.

09 BIOMASS FUELS

Application of Machine Learning to Improve Biobased Glucaric Acid Production: Cooperative Research and Development Final Report, CRADA Number CRD-20-17260

The Agile Biofoundry (ABF) is a multi-national lab consortium funded by the DOE Bioenergy Technologies Office that has developed a biofoundry that enables the rapid deployment of bioproducts into the market. Working with four ABF laboratory members (National Laboratory of the Rockies (NLR), Pacific Northwest National Laboratory (PNNL), Lawrence Berkeley National Laboratory (LBNL), and Argonne National Laboratory (ANL)), Kalion will use advanced high throughput techniques, advanced analytics, and machine learning to optimize the production environment for glucaric acid. Low-cost, high-purity glucaric acid enables products in a wide range of fields to improve the chemical properties of products and applications ranging from water treatment, polymers & textiles, coatings, detergents, and pharmaceuticals. With its broad range of applications, glucaric acid has the potential to demonstrate how such bio-based materials offer great benefit to the US economy.

09 BIOMASS FUELS

Greenhouse Gas Emissions Associated with Pretreatment Techniques Utilized for Biosugar Production

Less carbon-intensive production of biosugars from lignocellulosic materials can lead to improved manufacturing of biofuels and bioproducts. In this study, the production of biosugars is analyzed to understand the potential of producing bioproducts from biosugars with a low carbon intensity. Life-cycle assessment is conducted on five lignocellulosic feedstocks along with seven pretreatment techniques to produce biosugars as an important platform intermediate for producing bioproducts. The production of electricity using lignin with and without heat integration was also incorporated. In addition, seven bioproducts are analyzed for the estimation of the GHG emissions budget, which represents the emissions available to convert, separate, and upgrade biosugars into bioproducts within the 70% emissions reduction target. Corn stover-deacetylation and dilute acid pretreatment (CS-DDA) provide the lowest GHG emissions for biosugar (0.03 kg CO 2 eq/kg biosugar) and thereby the highest GHG emissions budget for the case of lactic acid production (3.76 kg CO 2 eq/kg lactic acid). Natural gas and chemicals are the major contributors to all of the pretreatment techniques under study. The outcomes from this study can benefit the advancement of upcoming biobased processes that meet decarbonization targets.

Biopolymers

Synthesis and Characterization of Soy Hull Biochar-Based Flexible Polyurethane Foam Composites

Flexible polyurethane foams are a diverse class of materials encompassing furniture, packaging, automotive, and many other industrial and domestic applications. Polyurethane foams are synthesized by the addition of polyols and isocyanates; however, the petroleum origin and toxic nature of isocyanates have driven many to look for more sustainable routes to production. Renewable fillers have emerged as a biobased resource to decrease the carbon footprint of this widely used polymeric material. In this study, soy hulls, as mass-produced, industrial by-products of soybean production, were used to create a biochar beneficial in the synthesis of flexible polyurethane foam composites. The addition of soy hull biochar was found to maintain the compression properties of foams at a decreasing isocyanate index, reducing the amount of isocyanates needed for production. In addition, the addition of biochar decreased the flammability of foams, important for many applications where consumer safety is important. The results point to the ability to create safer, more sustainable, and even more cost-effective polyurethane foams through the reduction in isocyanate use while maintaining the properties of this important class of polymers.

Chemistry