This study presents the development of sustainable, thermostable, and self-healable capacitors using poly(lactic acid) (PLA) as a bio-based dielectric. Stereocomplexation between high-molecular-weight poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was employed to form stereocomplex PLA (scPLA), increasing the melting temperature (T-m) from 175 degrees C (PLLA) to 220-230 degrees C (scPLA). Low-molecular-weight PLLA (similar to 30 kDa) and high-molecular-weight scPLA (>100 kDa) were synthesized via ring-opening polymerization and blended in varying ratios to exploit dual melting transitions and tailor thermal properties. The resulting hybrid PLA networks, comprising mobile PLLA within a rigid scPLA matrix, were processed into capacitors by layer-by-layer printing. These devices exhibited self-healing behavior and maintained dielectric performance after thermal cycling and electrical breakdown. Notably, the PLA-based capacitors operated at temperatures up to 190 degrees C-approximately 90 degrees C higher than commercial biaxially oriented polypropylene (BOPP) capacitors-demonstrating significantly enhanced thermal stability and extended service life.

Bio-based polymer building blocks can offer new molecular functionalities with lower environmental impact, but new production processes and purification affect purity and therefore polymerizability. This study explores a complete process chain for microbial 4-hydroxyphenylacetic acid (4HPAA) production from glucose using . Multiple biosynthetic pathways were engineered, enabling efficient 4HPAA production with a yield of up to 25% (Cmol Cmol-1). The process was optimized in shake flasks to enhance the productivity and scaled up to 30 and 1500 L stirred tank bioreactors, where product titers of 11 g L-1 were achieved in a fed-batch process. Downstream processing enabled kilogram-scale purification of 4HPAA but, more importantly, provided valuable insights into the effects of purification on subsequent polymerization of the monomer. The effects of strain engineering, scale-up, and purification on the purity of 4HPAA were assessed. Multiple 4HPAA samples from different downstream processing stages were polymerized and compared regarding the molecular weights and color of the resulting polymers. The use of bio-based 4HPAA with purities of >= 95% produced polymers comparable to a high-purity commercial 4HPAA. Overall, this study demonstrates the importance of an integrated approach of strain development, up- and downstream process engineering, and polymer science to enable sustainable production of bio-based monomers.

This study aimed to prepare liquid-filled hybrid network capacitors that are self-healing and maintain reliable performance at high temperatures by selectively cross-linking or branching polyethylene (PE) in the presence of low-molar-mass polypropylene (PP). PE was modified by reactive extrusion with different ratios of dicumyl peroxide in the presence of PP to prepare intermediates that could be injection molded into discs. During thermal processing, PE undergoes cross-linking or branching, while PP is known to undergo chain scissoring, resulting in the formation of a cross-linked or branched PE matrix that is responsible for improved thermostability. In contrast, the PP forms a mobile phase, which is responsible for self-healing. A range of peroxide concentrations was evaluated, confirming that structures from slightly branched to cross-linked could be obtained after extrusion and injection molding. Thin-film capacitors were subsequently fabricated by spin-coating inks on a conductive substrate and characterized to determine their dielectric performance. The optimal PE matrix structure was obtained with a low initiator loading, resulting in a branched structure with a relatively low dielectric constant (similar to 2.5), which resulted in improved thermostability up to 150 degrees C. Capacitor devices that experienced electrical breakdown were able to self-heal and function again after annealing at 160 degrees C.

Microwave irradiation is demonstrated as a screening method for the polymerization of crude terephthalic acid (TA) and crude bis(2-hydroxyethyl) terephthalate (BHET), obtained from the enzymatic hydrolysis and glycolysis of poly(ethylene terephthalate) (PET). The use of microwave irradiation and a reduced pressure of 40 mbar allows for the preparation of medium-long PET with measured Mw values up to 30-40 kg/mol relative to PMMA standards in less than 1 h. The versatility of the screening approach is demonstrated through the evaluation of a range of esterification and polycondensation catalysts using pristine starting materials. It was found that for the reaction between TA and EG using a Ti(OBu)4 catalyst, it yields the largest polymers, accompanied by minimal coloration. For the polymerization of BHET, the Sb2O3 catalyst produced large polymers with little coloration, while the use of the Ti(OBu)4 catalyst gives highly colored materials. The developed procedure is used to re-polymerize crude TA recovered from enzymatic degradation of PET waste as well as crude BHET recovered from glycolysis of pristine and waste PET. Repolymerization is possible, but the color and molecular weight of the final polymer are found to depend on the type and amount of impurities in the starting materials. The relevance of the formed intermediates as precursors for high molar mass PET was confirmed through solid-state polymerization that yielded high molar mass PET from selected samples.

Poly(4-hydroxyphenylacetic acid), PHPA is a bio-based aromatic polyester synthesized by polycondensation of 4hydroxyphenylacetic acid (HPA) in bulk. The liquid crystalline behavior of PHPA allows transesterification with commonly used polyesters like PLA, PETG, and PCL at relatively low temperatures to give multiblock copolymers that have a high blending compatibility with the parent polyester. The resulting polymer blends with PLA exhibit accelerated hydrolytic degradation compared to pristine PLA and a 36 % decrease of the flexural modulus of the blends of PLA containing up to 10 % of PHPA-PLA multiblock copolymers.

The suitability of different polyhydroxyalkanoate blends for the replacement of polypropylene in Novo Nordisk’s injection pen application was evaluated. Polyhydroxyalkanoate blends were analysed, each with varying ratios of PHAs, including poly-3-hydroxybutyrate-co-3-hydroxyvalerate, poly-3-hydroxybutyrate-co-3-hydroxyhexanoate, and poly-3-hydroxybutyrate-co-4-hydroxybutyrate, with variable talc compositions. The crystallisation kinetics, secondary crystallisation and mechanical properties were examined through differential scanning calorimetry and tensile testing. Lastly, a life cycle analysis and an environmental risk assessment were performed, and the influence of different crystallisation rates on processing cycle time was studied.The Avrami model was applied to isothermal crystallisation of the blends, it revealed that an equilibrated balance between semi-crystalline and amorphous polyhydroxyalkanoate, with shorter hydrocarbon chains and a small talc addition, accelerated crystallisation. Tensile tests indicated a higher strength and lower creep behaviour for blends that have a ratio close to 1:1. In addition, blends containing poly-3-hydroxybutyrate-co-3-hydroxyhexanoate exhibited lower tensile strains and toughness but a larger Young’s modulus. Life cycle assessment results demonstrated a carbon footprint reduction of 4 % with optimised composition.The blend containing 55 wt% poly-3-hydroxybutyrate-co-3-hydroxyvalerate and 45 wt% poly-3-hydroxybutyrate-co-3-hydroxyhexanoate with a low amount of talc exhibited the best potential based on all measured parameters, which was confirmed by successful moulding into a high-precision component.

Poly(ethylene terephthalate) (PET) is still a major player in the plastics industry, especially for packaging. Despite attempts to derive its basic components from biological resources, production of terephthalic acid (TPA), one of the two PET monomers, still depends on fossil resources. Alongside traditional polyesters, TPA is a building block also for biodegradable polymers, such as poly(1,4-butylene adipate-co-1,4-butylene terephthalate) (PBAT). Here, PET, PBAT, and real plastic waste were successfully depolymerized using Humicola insolens cutinase as an environmentally friendly alternative to mechanical or chemical treatments allowing recovery of TPA even from mixed plastic waste. This monomer was isolated in high purity upon acidification as confirmed by using Fourier Transform-Infrared Spectroscopy, 1H-NMR spectroscopy, and Thermogravimetric analysis. Consequently, contaminants or residual buffer salts caused major issues during synthesis of PET precursors upon reaction with ethylene glycol (EG) and TPA. The recovered TPA was used to prepare bis(hydroxyethyl) terephthalate (BHET) and further repolymerized to PET. The resulting molecular weight of the polyesters was found to be dependent on the purity of the TPA and on the catalyst used.

Both producers and end-users of silicone elastomers are facing a significant challenge regarding efficient recycling processes for their materials. The inherently stable nature of silicone elastomers gives them unique properties, but complicates their reentry to a circular material loop. This paper presents a recyclable silicone elastomer with crosslinks constituted by silyl ethers. Condensation curing of carbinol-functional polydimethylsiloxane (PDMS) with polysilazane (PSz) is proven to create a stable silicone elastomer without the need for a metal catalyst. The mechanical properties can be easily tuned by the addition of fillers as well as by chain extension. Adding the cured silicone elastomer to a solution of 0.055 mol L-1 acetic acid (AcOH) in tetrahydrofuran (THF) for 24 h at 40 degrees C yields a liquid silicone with a high resemblance to the starting polymer, demonstrating a selective cleavage of the silyl ether crosslinks. Experiments show that this reclaimed silicone can successfully be recured using new PSz to form new silicone elastomers. Mechanical properties similar to the starting elastomer are achieved when the reclaimed silicone is cured with pristine polymer in a 1:1 ratio, demonstrating the potential for industrial applications, where cured production scrap could be reintroduced to new elastomers via a simple process.

This study presents a novel one-pot procedure for preparing sub-10 μm poly(ethylene glycol) (MPEG)-stabilized glycol-modified poly(ethylene terephthalate), poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), polycarbonate, and polycaprolactone (PCL) particles from commercial plastics. The prepared particles can be dried and directly resuspended in water, making them easy to handle and relevant mimics of microplastics. In addition, the method was extended to the preparation of unstabilized PET particles and somewhat larger polyethylene (PE)-based particles. Selected stabilized microparticles were subjected to aerobic biodegradation studies and compared with nonstabilized PET particles. All of the particles exhibited some degradation. For PLA and PET particles, the degradation corresponded well to the amount of surface-stabilizing MPEG groups or known impurities, confirming that these polymers do not degrade under the applied conditions but that the stabilizing groups do. PCL particles degraded relatively rapidly, which is consistent with the literature data and their relatively small size. PE-based particles degraded more than expected if only degradation of the stabilizing groups was taken into account, indicating that the surface chemistry of these particles plays a role in bulk degradation.

Increased recycling of plastics is an essential step toward a more sustainable use of materials, where some of the most challenging fractions are engineering materials and composites. Used pump houses prepared from glass fiber (GF)-reinforced blends of polyphenylene oxide (PPO) and high-impact polystyrene (HIPS) obtained through a take-back scheme (take-back, TB) were characterized and shredded for use in the preparation of new composites by injection molding. Initial degradation was observed on the surface of the TB parts; however, the core of the material was unaffected. Mechanical reprocessing of regrind and virgin material showed a reduction of tensile strength already at 10% regrind, which was attributed to fiber length reduction during reprocessing. At the same time, Young's modulus and extension at break were largely unaffected, confirming that 25% of TB could be included without any additional loss of properties. As a worst-case scenario, tests with extensively degraded material showed that Young's modulus and tensile strength would ultimately be reduced with an increasing amount of heavily degraded material and that a balance would have to be found between loss of properties and recycled content for heavily degraded material.

The current work reports the chemical modification of polyolefins in presence of a free radical initiator via reactive extrusion. The crosslinked network is formed upon radical coupling during processing which is substantiated by viscoelastic measurements. The network formed consists of a polyethylene gel with free polypropylene with improved dielectric properties. The designed material is stable at elevated temperatures with an inherent self-healability which renders it a potential candidate as capacitor in power electronics.

study on submicron particles released from synthetic textiles provides insight into their origin and properties.

Thiol-maleimide conjugation is a well-established coupling method in biochemistry but with little reported use within silicone materials. A facile synthetic route of functionalised poly(dimethyl siloxane) (PDMS) to a prepolymer species capable of non-metal-catalysed cross-linking via thiol-Michael addition is presented. Two systems are compared: maleimide (MI) terminated PDMS and its precursor, maleamic acid amide (MA) terminated PDMS. Despite the traditional view of maleamic acid amide functionalities as being of inferior value to their maleimide counterparts, we argue for their potential. The increased relative concentration of polar groups in a robust MA network matrix can be exploited for better electrical properties for self-healable dielectric elastomer actuators, as demonstrated by the MA networks with their quadruple hydrogen bonding centres, self-healing capabilities, increased polarity, good electrical breakdown strength, and increased dielectric permittivity over both commercial and MI PDMS networks.

Decades of extensive and exponentially growing production and use of conventional plastics have led to the accumulation of plastic waste in the environment, contributing to the anthropocene pressure on ecosystems. Bioplastics (defined as bio-based and/or biodegradable plastics) have been promoted as a more sustainable alternative and substitute for conventional plastics. Nonetheless, the literature contains numerous conflicting conclusions regarding their suitability and environmental implications. One central point of contention concerns their biodegradability and the conditions necessary for proper degradation. In real-world settings, like anaerobic digestion plants or marine environments, biodegradable plastics may not degrade as rapidly or efficiently as suggested by laboratory tests. A systematic literature review was conducted to explore the current level of knowledge regarding the environmental fate and consequences of biodegradable plastics, thereby substantiating discussions on their future role in society. The review covered the degradation of biodegradable plastics in waste management environments (e.g., compost, sludge, or landfill) and the open environment (e.g., seawater, freshwater, or soil). As clearly highlighted by this review, comparisons and quantitative analysis of data on plastic degradation are challenged by significant methodological variations, encompassing differences in testing methods, test materials, and quantification strategies. Moreover, the review revealed several research gaps, highlighting, in particular, the need to i) intensify the research on polyhydroxyalkanoates (PHAs), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS) to match the level of polylactic acid (PLA) and starch-based plastics, ii) develop standard test methods in field conditions, and iii) couple degradation testing with ecotoxicological tests. The overview established in this review is essential for a more thorough evaluation of the environmental performance of biodegradable plastics. Furthermore, the findings of this study contribute to supporting the responsible future production and use of biodegradable plastics in various products, including assessing their role as alternatives to conventional plastics.

Poly-3-hydroxybutyrate (PHB) is a promising biopolymer that has the potential to replace fossil-based plastics yet is currently limited by its poor mechanical properties. A library of oligomeric polyesters containing adipates, furanoates, phathalates, and pyridinecarboxylates were enzymatically synthesized and evaluated as PHB additives. Across the series of additives, the pyradinecarboxylate oligoesters served as the most efficient plasticizers, whereas the phthalate was found to influence the rate of crystallization to the greatest extent. Due to the differences in additive miscibility, plasticization, and extent of crystallization, the compounds showed significantly different mechanical properties. Several additives promoted efficient crystallization at high cooling rates, such as phthalate oligomer P5, which resulted in a material that crystallized four times faster than pure PHB, and produced a material with smaller spherulites. This difference in morphology was to some extent reflected in the mechanical properties, as addition of PHB-P5 resulted in a 42% decrease in the Young's modulus. Overall, the combined effects of the degree and rate of crystallization, as well as the nature of the amorphous phase, prevented obvious trends from emerging.

This study explores the influence of mold temperatures below 60 degrees C on thermoplastic polyurethane (TPU) properties during injection molding, focusing on phase separation and its impact on mechanical, thermal, and viscoelastic properties. Using a combination of micro-indentation, temperature scanning stress relaxation, and conventional characterization methods, the research highlights how increased mold temperatures promote more distinct phase separation, enhancing mechanical stability and physical properties. The novel use of micro-indentation revealed a gradient in material stiffness from the surface to the core of injection-molded samples, attributed to differential cooling rates and shear forces, which affect phase separation and crystallinity of the hard domains. These insights are critical for applications requiring specific surface properties and underscore the importance of understanding the interplay between chemical composition and processing conditions for optimizing TPU properties. Furthermore, the paper shows that tensile testing, differential scanning calorimetry, and Shore hardness cannot quantify the effects of mold temperatures below 60 degrees C. The research highlights the influence and importance of chemical composition, rheological history, and thermal history on the properties of TPU.

Poly(ethylene glycol)- block -polycaprolactone copolymers with different architectures, dispersities and end-groups were prepared and found to form a variety of self-assembled structures in water.

Abstract The environmental fate and impact of microplastics as well as their possible physiological effects, are expected to depend on their physico-chemical characteristics, including polymer types and surface chemistry. There is thus a clear need to develop a broad range of model microplastic particles to study the fate and effects of environmentally relevant microplastics. Here, a simple one-pot procedure to prepare sub-10 µm poly(ethylene glycol) (MPEG)-stabilised glycol modified poly(ethylene terephthalate) (PETG), poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), polycarbonate (PC) and polycaprolactone (PCL) particles is described. The prepared particles can be dried and directly re-suspended in water, making them easy to handle and relevant mimics of microplastics. In addition the method was extended to prepare somewhat larger polyethylene-based (PE) particles and control PET particles were also prepared. Selected microparticles were subjected to aerobic biodegradation studies and compared with non-stabilised PET particles. All particles exhibited some degradation. For PLA and PET particles, the degradation corresponded well to the amount of surface stabilising MPEG groups or known impurities, confirming that these polymers do not degrade under the applied conditions but that the stabilising groups do. PCL particles degraded relatively rapidly, consistent with literature data and their relatively small size. PE-based particles degraded more than expected if only degradation of the stabilising groups was taken into account, indicating that the surface chemistry of these particles plays a role in bulk degradation. These studies thus demonstrate the effect of varying the type of polymer and improves the understanding of how surface chemistry affects the degradation of microparticles.

In the context of a green transition, alternatives to fossil-based aromatic compounds have to be implemented. In this study, the combination of sequential solvent fractionation followed by depolymerization via catalytic hydrogenolysis of lignin led to liquid oligomeric lignin structures with chemical properties governed by the choice of lignin soluble fraction. Lignin species of increasing molecular weight (MW) were obtained with MW reduction up to 72% compared to the parent lignin, with a corresponding increase in total hydroxyl content up to 18% obtained through cleavage of lignin ether bonds. Hydrogenolysis led to lignin depolymerization oils comprising macromolecular lignin fragments and app. 15-18 wt % lignin monomers, resulting in a liquid product mixture. The lignin species were epoxidized to show their potential as a bio-based aromatic substitute to fossil-based bisphenol A. Liquid epoxy resins were obtained with viscosities between 2 x 103 and 4 x 105 Pa center dot s, which after curing resulted in thermoset networks with Young's moduli between 0.9 and 1.4 GPa depending on the lignin fraction. Optimal viscosity to mechanical performance was obtained for ethyl acetate and ethanol solvent fractionated and depolymerized lignins as lower viscosity allows for reduced use of volatile organics.