Bio-based lactone acrylic plastics with performance and recyclability advantages
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36 MATERIALS SCIENCE↗
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Results for “recyclable vinyl polymers”
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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Simultaneous Degradation‐Depolymerization of Bioderived Comb Copolymers
Poly(lactic acid) (PLA) is the most widely explored biodegradable alternative for polystyrene; however, its low toughness and glass transition temperature may limit its wider adoption as a sustainable replacement. To improve its material and thermal properties, PLA can be chemically or physically combined with other polymers, like poly(methyl methacrylate) (PMMA), though the incorporation of vinyl‐based polymer components complicates chemical recycling and reduces the sustainability of the material. Here, in this study, we synthesized polymethacrylate‐PLA comb copolymers designed to be thermally deconstructed. Our design strategically extends current polymer deconstruction methodologies to more complex macromolecular systems. Thermally labile units within the polymethacrylate backbone permitted depolymerization that was concurrent with PLA side chain degradation during heating. This dual degradation‐depolymerization process enhances the overall sustainability of lactide/vinyl‐based copolymers and demonstrates the synergistic potential of integrating multiple deconstruction pathways into a single system. This report elaborates on the design of advanced, degradable copolymers, contributing to the further development of sustainable polymer materials.
PLA↗
Electrochemically Initiated Depolymerization of Poly(Methyl Methacrylate)
Efficient depolymerization of polymers with all-carbon backbones under mild conditions would be valuable in chemically recycling commodity plastics. Poly(methyl methacrylate) (PMMA) is a commodity thermoplastic that is currently depolymerized under temperatures in excess of 400 °C. Herein, we lower the temperatures needed to achieve depolymerization of PMMA by performing radical generation and depropagation with orthogonal stimuli. This first demonstration of electrochemically initiated PMMA depolymerization relies on reduction of phthalimide esters that, upon subsequent decarboxylation, generate polymer-centered radicals. These radicals then spontaneously unzip the polymer back to its monomeric constituents at temperatures as low as 105 °C. We studied the mechanism and efficiency of this transformation as a function of phthalimide ester placement, incorporation density, and polymer molecular weight. We found that chain-end activation is effective for modest molecular weights but suffers diminished efficiency at higher degrees of polymerization. In contrast, pendent-group activation is more effective for depolymerizing higher molecular weight species. Integrating higher molar amounts of phthalimide ester pendants leads to more effective depolymerization, with >95% depolymerization in copolymers with 5 mol% phthalimide ester incorporation. We leveraged this understanding to create a custom electro-distillation apparatus that allowed us to simultaneously electrochemically depolymerize PMMA and directly distill methyl methacrylate in >22% yield, which could ultimately be repolymerized. These findings establish electrochemistry as a versatile and orthogonal stimulus for vinyl polymer depolymerization and provide a foundation for closed-loop electrochemical recycling of widely used plastics.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Recycling of multilayer plastic packaging materials by solvent-targeted recovery and precipitation
Many plastic packaging materials manufactured today are composites made of distinct polymer layers (i.e., multilayer films). Billions of pounds of these multilayer films are produced annually, but manufacturing inefficiencies result in large, corresponding postindustrial waste streams. Although relatively clean (as opposed to municipal wastes) and of near-constant composition, no commercially practiced technologies exist to fully deconstruct postindustrial multilayer film wastes into pure, recyclable polymers. Here, we demonstrate a unique strategy we call solvent-targeted recovery and precipitation (STRAP) to deconstruct multilayer films into their constituent resins using a series of solvent washes that are guided by thermodynamic calculations of polymer solubility. We show that the STRAP process is able to separate three representative polymers (polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate) from a commercially available multilayer film with nearly 100% material efficiency, affording recyclable resins that are cost-competitive with the corresponding virgin materials.
36 MATERIALS SCIENCE↗
Revisiting the activity of two poly(vinyl chloride)- and polyethylene-degrading enzymes
Biocatalytic degradation of non-hydrolyzable plastics is a rapidly growing field of research, driven by the global accumulation of waste. Enzymes capable of cleaving the carbon-carbon bonds in synthetic polymers are highly sought-after as they may provide tools for environmentally friendly plastic recycling. Despite some reports of oxidative enzymes acting on non-hydrolyzable plastics, including polyethylene or poly(vinyl chloride), the notion that these materials are susceptible to efficient enzymatic degradation remains controversial, partly driven by a general lack of studies independently reproducing previous observations. Here, we attempt to replicate two recent studies reporting that deconstruction of polyethylene and poly(vinyl chloride) can be achieved using an insect hexamerin from Galleria mellonella (so-called “Ceres”) or a bacterial catalase-peroxidase from Klebsiella sp., respectively. Reproducing previously described experiments, we do not observe any activity on plastics using multiple reaction conditions and multiple substrate types. Digging deeper into the discrepancies between the previous data and our observations, we show how and why the original experimental results may have been misinterpreted.
36 MATERIALS SCIENCE↗
Reducing Antisolvent Use in the STRAP Process by Enabling a Temperature–Controlled Polymer Dissolution and Precipitation for the Recycling of Multilayer Plastic Films
The recently reported processing strategy called solvent-targeted recovery and precipitation (STRAP) enables deconstruction of multilayer plastic packaging films into their constituent resins by selective dissolution. It uses a series of solvent washes that are guided by thermodynamic calculations of polymer solubility. In this work, the use of antisolvents in the STRAP process was reduced and solvent mixtures were considered to enable the temperature-controlled dissolution and precipitation of the target polymers in multilayer films. This was considered as a means to further improve the STRAP process and its estimated costs. Two STRAP approaches were compared based on different polymer precipitation techniques: precipitation by the addition of an antisolvent (STRAP-A) and precipitation by decreasing the solvent temperature (STRAP-B). Both approaches were able to separate the constituent polymers in a post-industrial film composed primarily of polyethylene (PE), ethylene vinyl alcohol (EVOH), and polyethylene terephthalate (PET) with near 100 % material efficiency. Technoeconomic analysis indicates that the minimum selling price (MSP) of the recycled resins with STRAP-B is 21.0 % lower than that achieved with STRAP-A. This provides evidence that thermally driven polymer precipitation is an option to reduce the use of antisolvents, making the STRAP process more economically and environmentally attractive. A third process, STRAP-C, was demonstrated with another post-industrial multilayer film of a different composition. Here, the results demonstrate that this process can also recover polymers at similar costs to those of virgin resins, indicating that the STRAP technology is flexible and can remain economically competitive as the plastic feed complexity is increased.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
6.26 Low Cost Basalt Fiber for Automotive Applications
Vehicle lightweighting is an essential component to the automotive industry to improve fuel economy of internal combustion engine (ICE) vehicles to meet ever improving emission standards and to improve the range of electric vehicles (EV). Composite materials offer high specific modulus and specific strength, which makes them appealing for these light weighting efforts. Sheet molding compounds (SMC) are particularly interesting from an automotive perspective because of the relatively low cost and high volume of producing SMC parts. Traditionally, composite materials for automotive application are glass fiber reinforced because of the attractive price - performance ratio, but basalt fibers are a cost and recycling competitive reinforcement alternative in this market. The aim of this project was to examine the feasibility of utilizing basalt fiber for automotive applications. More specifically, an effort was made to examine different fiber sizings on basalt fiber combined with vinyl-ester (VE) resin, and their performance as part of an SMC process. In addition to offering vehicle lightweighting with fiber reinforced polymer composites, basalt fiber is a fully recyclable material and thus supports the IACMI technical goal of: Demonstrate that the technology is capable at a sufficient scale for >80% recyclability or reuse of fiber reinforced polymer composites in five years into useful components with projected cost and quality at commercial scale competitive with virgin materials on a pathway to 95% recyclability or reuse starting in ten years. Three different fiber sizings were applied to a continuous roving of basalt fiber and compared to a traditional Electrical/Chemical Resistance (E-CR) glass fiber that is typically used in these types of applications. Fiber tows were examined for Loss on Ignition percentage (LOI%), Tex, and tow strength. Some sizings clearly outperformed others, and the ability to process these fibers on a pilot scale SMC line was demonstrated. A test plan for the manufacturing and mechanical testing of SMC panels was developed. This work continues outside the time frame allocated for this project. When this work is completed, it will be added to this report and posted as Appendix C. Glass fiber reinforced SMC materials have already proven feasible as a light weighting method for traditionally steel parts like the Volkswagen (VW) Atlas lift-gate (Figure 1); this project team is seeking the feasibility of basalt fiber as a drop-in replacement for glass fiber reinforced SMC. Sizing development for basalt fibers has proven that the mechanical properties are better than E-glass and closer to S-glass, which makes it an interesting material for SMC applications. Better mechanical properties translate to less material needed to achieve load case requirement for target applications. The business case has already been demonstrated for 100,000 parts per year of glass fiber reinforced SMC Atlas lift-gates compared to traditional steel manufacturing processes. Reduced overhead and assembly costs are offset by glass fiber SMC higher cost per kg beyond 100,000 parts per year, which is still a relatively low volume for the automotive industry. For basalt fiber reinforced SMC to become feasible for automotive applications, the price-performance ratio has to be precisely determined. Based on the mechanical performance it is possible to establish a range of applications and technical solutions in which the potential of basalt SMC can be utilized, while the price of the material can be used to compile the business case for such applications. Based on these business cases and the sustainability indicators, glass fiber reinforcement (or other) materials can be directly substituted. Volkswagen’s commitment to reducing carbon emissions cannot be understated. Basalt fiber shows promise of reducing the carbon footprint in SMC materials, especially if sizing optimizations can be made with thermoplastic based SMC. To fully realize the value of basalt fiber reinforced materials, a lifecycle cost analysis should be performed on basalt’s production and recycling, and then compared against E-glass. From this assessment, a true judgement can be made on the commercialization potential of this material. Figure 1. Example of Fiber Reinforced Polymer Composite Liftgate As a conclusion, we can state that Mafic basalt fiber is not a direct replacement for E-glass or E-CR glass based on price, but should be considered a technical solution when E-glass does not provide adequate performance in a composite design and S-glass, aramid and carbon fibers are too costly. Mafic basalt fiber can be placed on the high-performance fiber spectrum next to S-glass for performance but at one third the price. It should be considered for more technically challenging structural designs wherein the performance can demonstrate 20-25% performance enhancement over E-glass to elicit more strength or a weight reduction. Both Michelman and Mafic produce thermoplastic sizings which, in combination with Nylon and polypropylene resin and fibers, can further advance high speed composite implementations while maintaining an eco-friendly manufacturing process.
36 MATERIALS SCIENCE↗
Dynamic Diketoenamine Crosslinking Unlocks Vinyl Polymer Vitrimers From β ‐Triketone Chemistry
Covalent adaptable networks (CANs) offer a compelling strategy to unite the mechanical robustness of thermosets with the reprocessability of thermoplastics, yet achieving simultaneous durability, processability, and true recyclability remains challenging. We introduce diketoenamine (DKE) vitrimers derived from β-triketone methacrylate monomers and demonstrate how rational monomer design dictates network processability, viscoelasticity, and recyclability. By systematically varying the spacer length between the β-triketone (TK) moiety and the polymer backbone, we identify a key structure–property relationship that dictates vitrimer behavior. Networks bearing TK pendants minimally displaced from the backbone suppress creep but exhibit limited stress relaxation, whereas extended spacers yield lower glass transition temperatures, higher effective crosslink densities, and efficient stress dissipation, enabling optical transparency and reprocessability. Extending this platform to ultra-high molecular-weight prepolymers introduces physical entanglements as secondary crosslinks, further enhancing dimensional stability without compromising processability. Both mechanical and chemical recycling validate the closed-loop circularity of these materials. Furthermore, these results establish TK methacrylates as a versatile platform for designing high-performance vitrimers that integrate durability, reprocessability, and true closed-loop recyclability.
closed-loop recyclability↗
Polymers depolymerizable by metathesis of a cleavable unit
Novel polymers are depolymerizable by metathesis of a cleavable unit. As an example, a series of linear and crosslinked polyurethanes were prepared that can be selectively depolymerized under mild conditions. Two unique polyols were synthesized bearing unsaturated units in a configuration designed to favor ring-closing metathesis to five- and six-membered cycloalkenes. These polyols were co-polymerized with toluene diisocyanate to generate linear polyurethanes and trifunctional hexamethylene- and diphenylmethane-based isocyanates to generate crosslinked polyurethanes. The polyol design is such that the ring-closing metathesis reaction cleaves the backbone of the polymer chain. Upon exposure to dilute solutions of Grubbs' catalyst under ambient conditions, the polyurethanes were rapidly depolymerized to low molecular weight, soluble products bearing vinyl and cycloalkene functionalities. These functionalities enabled further re-polymerization by traditional strategies for polymerization of double bonds. This general approach can be expanded to develop a range of chemically recyclable condensation polymers that are readily depolymerized by orthogonal metathesis chemistry.
Jones, Brad Howard↗
Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis
This communication describes a novel series of linear and crosslinked polyurethanes (PUs) and their selective depolymerization under mild conditions. Two unique polyols are synthesized bearing unsaturated units in a configuration designed to favor ring-closing metathesis (RCM) to five- and six-membered cycloalkenes. These polyols are co-polymerized with toluene diisocyanate to generate linear PUs and trifunctional hexamethylene- and diphenylmethane-based isocyanates to generate crosslinked PUs. The polyol design is such that the RCM reaction cleaves the backbone of the polymer chain. Upon exposure to dilute solutions of Grubbs’ catalyst under ambient conditions, the PUs are rapidly depolymerized to low molecular weight, soluble products bearing vinyl and cycloalkene functionalities. These functionalities enable further re-polymerization by traditional strategies for polymerization of double bonds. We anticipate that this general approach can be expanded to develop a range of chemically recyclable condensation polymers that are readily depolymerized by orthogonal metathesis chemistry.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Delamination recycling of multilayer plastic films: Solvent-assisted separation pathways and recovery of solid polyolefins
Multilayer plastic films are excellent packaging materials due to the bound layers of multiple polymers, with each different polymer contributing to the film properties. Desirable properties lead to continuously growing demand for multilayer films. Multilayer plastic films are typically single-use and, as such, their increased production and disposal have led to waste management problems. Multilayer films are not currently recyclable primarily due to the multiple bound polymers. This work advances delamination as a recycling process to separate and sequester valuable polymers from multilayer films, facilitating the incorporation of these polymers into the circular economy. We effect delamination in a physical process that preserves targeted polymers as solid film, hence retaining their embodied energy. This work documents three different pathways of inducing delamination of multilayer films, with appropriate solvents disrupting adhesion between adjacent layers or dissolving a minor component of the film in less than an hour and at temperatures below 90°C, and where all initial polyethylene is maintained in its solid form throughout the process and is recovered at high purity. Solvent-based delamination is exemplified on commercial multilayer films with majority polyethylene (PE), and polyethylene terephthalate (PET) or ethylene vinyl alcohol copolymer (EVOH) or nylon also present. Solvent-based delamination is an energy-efficient and environmentally friendly recycling process that improves upon dissolution-precipitation recycling, since delamination involves very little dissolution and no precipitation, and is superior to pyrolysis which breaks down the polymers, while delamination keeps polymer chains intact. Furthermore, delamination recycling can contribute to the sustainable use of multilayer films as they continue to protect our food and medicine.
Chemical Recycling↗
Computational Approach for Rapidly Predicting Temperature–Dependent Polymer Solubilities Using Molecular–Scale Models
One promising approach to recycle multicomponent plastic waste (e. g., multilayer plastic films) is selective dissolution. Selective dissolution is a solvent-mediated process in which differences in polymer solubility in a carefully chosen solvent system are exploited to recover a target polymer. Here, a computational approach was developed that rapidly predicts temperature-dependent polymer solubilities to guide the design of solvent systems for solvent-mediated polymer recycling. Polymer conformations were obtained from molecular dynamics simulations by modeling the polymer as a short oligomer and then used as input to the conductor-like screening model for real solvents (COSMO-RS) for solubility predictions. Using polyethylene (PE) and ethylene vinyl alcohol (EVOH) as representative polymers, the effect of simulation parameters was systematically studied, and predicted solubilities were found to be in good agreement with experimental measurements. Furthermore, the applicability of the approach was demonstrated by identifying selective solvents for PE and EVOH dissolution from a library of 524 solvents.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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↗
Mechanistic insights into the conversion of polyalcohols over Brønsted acid sites
Multi-layered plastic (MLP) films provide excellent properties for food packaging; however, because of the complicated chemistry of the hydrophobic substrates and tightly laminated hydrophilic layers, it is challenging to recycle the MLP films. The selective conversion of polar functional groups in hydrophilic layers with a minimal destruction of the carbon backbone of constituted polymers is considered a promising approach to improve the recyclability of MLP films. Here, in this study, we combine computational and experimental studies to investigate the acid-catalyzed conversion of functional groups in polyalcohols, through which we report potential reaction pathways involved in the conversion of ethylene vinyl alcohol (EVOH), a common copolymer used in MLP films as an oxygen barrier. Using 2,4-pentanediol as a model compound, we show that its conversion proceeds primarily through the dehydration of a hydroxyl group via either a stepwise or a concerted mechanism to form an unsaturated alcohol that can be further converted into a conjugated diene or a saturated ketone; this secondary reaction determines the product selectivity. The rate determining intermediates and transition states are identified, and the activation barriers are calculated, in agreement with experimentally observed product selectivities. This study thus provides insights for the selective conversion of EVOH.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Recycling of a post-industrial printed multilayer plastic film containing polyurethane inks by solvent-targeted recovery and precipitation
The recently reported Solvent-Targeted Recovery And Precipitation (STRAP) strategy is used to deconstruct multilayer plastic packaging films into their constituent resins by selective polymer dissolution. To broaden the applicability of STRAP, we demonstrate the process with a flexible post-industrial printed multilayer plastic film used for food packaging. The material was a reverse printed film composed of polyethylene (PE), ethylene vinyl alcohol (EVOH), polyethylene terephthalate (PET), and polyurethane (PU)-based inks. Removal of all colors was observed with biomass-derived gamma-valerolactone (GVL) and the recovered polymers possessed comparable properties to the corresponding virgin resins. A technoeconomic analysis indicates that this STRAP process could be economically feasible at a processing capacity of 6,000 tons per year. Furthermore, the production of plastic films with materials recovered by this STRAP process can have a lower climate change impact than the production of films from virgin polymers.
54 ENVIRONMENTAL SCIENCES↗
Techno-Economic and Life Cycle Assessment of Chemical Recycling and Upcycling of Mixed Plastics Waste Containing Poly-vinyl-chloride
Developing technologies that completely remove chlorine from plastic waste can allow its chemical recycling and upcycling with catalytic methods. Here, this study compares eight processes involving different dechlorination methods (absorption columns, adsorption in beds of zeolites, catalytic dechlorination, and dissolution in ionic liquids) and chemical conversion technologies (incineration, pyrolysis, hydrogenolysis) to upgrade mixed plastics waste to various products (e.g., electricity, fuels, virgin polymers, and lubricant oil). The analysis determines that the absorption of chlorine in columns with basic aqueous solutions is limited to plastics waste with PVC concentrations below 0.1%. Dissolution in ionic liquids is not cost-competitive. On the contrary, two-step processes with catalytic dechlorination followed by thermochemical catalytic depolymerization, either pyrolysis or hydrogenolysis, significantly improve process economics and emissions. The most economically viable alternative is hydrogenolysis for producing lubricants, while the technology with the lowest global warming potential is chemical recycling via catalytic pyrolysis.
circular economy↗
On electron beam-induced degradation of vinyl ester thermosets
We have demonstrated that electron beam radiolysis induces scissions of the C-O-C bonds along the backbone of the chains of unsaturated polyester thermosets of different compositions based on dicyclopentadiene, isophthalic acid, epoxy vinyl ester, and terephthalic acid. The radiolysis is imminent irrespective of the degree of crosslinking in the thermosets both in neat resins and in the presence of solvents. Electron Paramagnetic Resonance (EPR) results show the formation of the alkoxyl radicals and C-centered radicals as the primary intermediate products of the C-O-C scissions. While the alkoxyl radicals of these resins exhibit very good stability even six months after the irradiation, the C-centered radicals decay very rapidly via their reactions with oxygen that is available either as adsorbed in the resins, dissolved in solvents or from the environment. The radiolytically produced •OH radicals in the unsaturated-ester aqueous solutions play a major role in inducing scissions on the backbone of the polymer chains. The solvated electrons (e s ) from organic solvents, such as dimethyl sulfoxide and isopropyl alcohol, also induce direct scission of the C-O-C bonds, giving rise to the formation of alkoxyl radicals and C-centered radicals. However, a considerable fraction of es is scavenged by the dissolved O 2 to produce O 2 - . Despite the radiation-induced scissions, irradiation of the resins at a dose level of 1000 kGy results in an increase of the glass transition temperature, Tg. This is due to the simultaneous radiation-induced polymerization of the vinyl monomers, toluene, and styrene that are present in the resins. The increase in Tg is observed in all the resins except for the terephthalic polyester resin in aqueous solution, in which the absence of these monomers results in Tg decreasing sharply with irradiation. This work demonstrates that ionizing radiation triggers continuous free radical-chain reactions that lead to the formation of recyclable oligomers.
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
Depolymerization of Vinyl Polymers
Depolymerization is a promising approach to reduce plastic waste by regenerating monomers from polymers, presenting a compelling solution to maintain a circular polymer economy. However, vinyl polymers with all-carbon backbones are especially difficult to depolymerize due to significant thermodynamic and kinetic barriers. Developments in reversible-deactivation radical polymerization and catalytic methods demonstrate how tuning polymer structure and reaction conditions can address these challenges. This Viewpoint revisits early studies on radical depolymerization and recent advances enabling monomer recovery at lower temperatures. Exciting current trends to utilize depolymerization as a strategy for tuning polymer material properties and upcycling waste polymer to high-value products are discussed. Finally, we outline key directions to make vinyl polymer depolymerization scalable, efficient, and economically viable.
depolymerization↗