Search Results (98)

Modern separation and purification technologies increasingly require materials that combine high selectivity, chemical robustness, and long-term operational stability without compromising mechanical performance. Radiation- and radical-induced graft copolymerization addresses this need by generating radical sites on polymer backbones and introducing tailored functional groups through subsequent monomer grafting. Retention of bulk properties, however, depends on controlling radiation dose, polymer structure, oxygen, and irradiation conditions so that grafting is favored over chain scission, crosslinking, and embrittlement. This review critically examines recent grafting strategies for gas and liquid separation, water treatment, radionuclide management, and resource recovery. It relates radical generation, graft growth, structural control, and functional-group chemistry to material performance and process optimization. Attention is given to radiation-induced grafting and its integration with controlled radical polymerization, especially reversible addition–fragmentation chain-transfer polymerization, to regulate graft density, chain length, and architecture. Composite and interfacial approaches are also evaluated. The review discusses the requirements and remaining barriers to practical translation, including dose optimization, long-term stability, regeneration, reproducibility, scalability, and the need for techno-economic and life-cycle assessments. Full article

Poly(methyl methacrylate) (PMMA), as a widely used transparent polymer material, is highly stable because of its all-carbon backbone, which makes its chain cleavage under mild conditions challenging. In this work, we report a photo-initiated solution reaction that induces main-chain scission of PMMA at room temperature, leading mainly to molecular-weight reduction and oligomer formation. This method requires no catalysts and does not need pre-introduction of specific groups. The degradation mechanism proposed according to DFT calculations involves the photolysis of trichloromethane to produce phosgene, which then reacts with ester groups on the side chains of PMMA to form acyl chloride groups. These acyl chloride groups further cleave under light or heat, generating radicals that trigger β-scission of the PMMA main chain through a side-chain-initiated pathway. The degradation mechanism was demonstrated experimentally, and the extent of chain scission can be regulated by temperature, O₂ and an alcohol stabilizer. Full article

Chemical glycolysis can convert waste poly(ethylene terephthalate) (PET) into bis(2-hydroxyethyl) terephthalate (BHET), but recyclable heterogeneous catalysts derived from circular carbon sources and showing low metal release remain limited. Here, post-consumer expanded polystyrene (EPS) was transformed into a hypercrosslinked polymer (HCP) and carbonized with Fe to produce Fe@graphitic-carbon (Fe@C) catalysts for PET glycolysis. The catalysts are denoted mFe@EPS-HCP₈₀₀, where m represents the nominal Fe loading (wt.%), and 800 is the carbonization temperature (°C). The optimized 5Fe@EPS-HCP₈₀₀ contained graphitic carbon layers, bamboo-like carbon nanotube (CNT) domains, hierarchical porosity, and Fe-rich domains associated with graphitic carbon coverage. Under atmospheric-pressure conditions (PET, 2.00 g; ethylene glycol, 20.00 g; catalyst, 0.20 g; 200 °C; 2 h), it achieved complete PET conversion and 94.6% BHET yield. The catalyst also maintained BHET yields of ca. 90–94% over ten reuse runs, and post-reaction microscopy confirmed the retention of graphitic carbon layers and Fe-containing domains. Fe was below the detection limit in the product solutions for the 1, 3, and 5 wt.% Fe catalysts, whereas 7Fe@EPS-HCP₈₀₀ released 9.1 mg kg⁻¹ Fe, consistent with incomplete carbon coverage at excessive Fe loading. Conversion profiles followed an Avrami–Erofeev/Weibull model, giving an apparent activation energy of 205.6 kJ mol⁻¹. The data support a two-stage pathway in which external graphitic carbon/CNT domains promote primary PET chain scission to soluble oligomers, followed by Fe@C interfacial secondary glycolysis to BHET. This work demonstrates dual waste-polymer valorization by using EPS waste as catalytic infrastructure for PET chemical recycling. Full article

Microbial enzymes have attracted considerable attention as biocatalysts for plastic transformation, yet the experimental evidence supporting reported biodegradation varies substantially in quality and interpretation. Surface-sensitive techniques, molecular-weight analyses, identification of transformation products, microbial assimilation assays, and carbon-tracking approaches each validate different stages of polymer transformation, but they are often treated as equivalent evidence of biodegradation. This review critically examines the analytical basis of enzyme-mediated plastic and microplastic transformation and introduces the Evidence-Level Framework (ELF), which classifies studies according to the highest experimentally validated transformation endpoint, from microbial colonization (ELF 0) to polymer-derived carbon conversion (ELF 5). Systematic screening identified 102 eligible experimental studies from an initial dataset of 150 publications, all of which were classified using the ELF to provide a comprehensive assessment of the current evidence landscape. Most studies clustered within intermediate evidence levels (ELF 2–3), where analytical validation was limited to polymer chain scission or the detection of soluble transformation products. By contrast, only a small proportion demonstrated microbial assimilation or unequivocal polymer-derived carbon conversion. Hydrolysable polyesters and their associated hydrolytic enzymes consistently reached the highest ELF categories because their chemical structure, enzymatic accessibility, and analytical tractability facilitate validation of successive transformation stages. Conventional plastics, however, remain constrained by polymer recalcitrance, limited substrate accessibility, microbial metabolic capacity, and the scarcity of analytical approaches capable of tracking polymer-derived carbon through biological systems. By providing a common framework for interpreting transformation claims, the ELF establishes objective criteria for experimental design, analytical validation, and comparison across independent studies, offering a stronger foundation for more reproducible, mechanistically robust, and environmentally relevant research on microbial plastic transformation. Full article

Textile waste is no longer dominated by simple single-polymer materials. Most post-consumer textiles contain combinations of natural and synthetic fibres, elastane, dyes, coatings, finishes, and other additives, which makes selective recycling considerably more difficult. Deep eutectic solvents (DES) offer a promising route for addressing this complexity because their composition and physicochemical properties can be widely tuned. However, the outcome of DES treatment is often discussed mainly in terms of solvent composition or solvent–polymer affinity, although these factors alone cannot explain why similar DES formulations may lead to different responses in different polymeric or textile systems. In this review, DES-assisted textile recycling is examined from a mechanistic polymer-science perspective. The discussion focuses on how polymer morphology, transport accessibility, supramolecular organization, chemical reactivity, and processing conditions jointly determine whether a material undergoes swelling, molecular dissolution, structural destabilization, or chemical degradation. Particular attention is paid to the distinction between these processes, since changes in sample mass, fibre appearance, or crystallinity do not by themselves prove either true polymer dissolution or chain scission. Evidence from cellulose-based fibres, polyesters, polyamides, polyurethanes, elastane-containing materials, and multicomponent textile systems is used to show how different material outcomes may arise from apparently related DES–polymer interactions. The reviewed studies indicate that selectivity in DES-assisted textile recycling should not be treated as a fixed property of the solvent or of the polymer alone. It is more appropriately understood as the result of a coupled and time-dependent interaction between the DES medium, polymer morphology, textile architecture, and processing conditions. The mechanistic framework proposed here provides a basis for comparing reported DES-based recycling strategies, identifying the experimental evidence needed to support mechanistic claims, and guiding the rational selection of DES composition, process conditions, and recovery pathways for complex textile waste. Full article

In this study, we evaluated the influence of physicochemical aging on the biological processing and depolymerization performance of polyethylene (PE) and polylactic acid (PLA) by Tenebrio molitor larvae, with the goal of improving insect-based plastic treatment strategies. PE and PLA subjected to a sequential freezing–ultraviolet aging protocol showed modest increases in total larval consumption (approximately 11% for PE and 10% for PLA) compared with pristine materials. Aging also accelerated the processes related to chemical depolymerization, as evidenced by Fourier transform infrared spectroscopy and scanning electron microscopy showing the formation of oxidized functional groups and surface structural deterioration, respectively. Gel permeation chromatography indicated significant reductions in molecular weight. In addition, thermogravimetric analysis was used to evaluate the changes in thermal stability associated with polymer degradation. Gut microbiome analysis revealed that plastic diets and aging collectively shaped microbial structure and compositional shifts, with deterministic ecological processes dominating community assembly. PE diets enriched Proteobacteria, while PLA diets enriched Firmicutes and Desulfobacterota. Notably, aging strengthened microbial cooperation and enriched key genera, such as Spiroplasma sp. and Lactobacillus sp., which are potentially associated with plastic-associated metabolic adaptation. Overall, aging modestly facilitated larval processing and partial depolymerization of both fossil-based and bio-based plastics, as reflected by increased plastic consumption, polymer chain scission, and surface oxidation. It also enhanced the functional robustness of the larval gut microbiome. These findings provide mechanistic insights into insect-mediated plastic processing systems, offering mechanistic guidance for future, combined plastic treatment strategies rather than an immediately scalable stand-alone solution. Full article

To elucidate the formation of crosslinked products and their influence on material degradation, thermoplastic polyurethane (TPU) films were subjected to accelerated UV aging for various durations. Post-aging, the samples underwent Soxhlet extraction with tetrahydrofuran (THF), yielding an insoluble fraction—operationally defined as the crosslinked product—and a soluble uncrosslinked fraction. The mechanical properties, molecular weight distribution, swelling behavior, thermal properties, and chemical structure were analyzed. As UV aging progressed, both tensile strength and elongation at break deteriorated markedly. Concurrently, GPC analysis revealed a continuous decrease in molecular weight and a broadening of the molecular weight distribution, confirming that chain scission was the dominant degradation pathway. An insoluble network-like residue, defined as the crosslinked product, first appeared after 12 h of aging, with its content increasing to 22.9% after 300 h. Swelling tests showed that the crosslinked product had a high gel fraction, and its swelling ratio decreased from 196.8% to 157.4%, indicating the formation of a stable and increasingly dense network. DSC and TG results revealed restricted segmental motion, altered thermal transition behavior, and enhanced char-forming ability. The glass transition temperature of the crosslinked product exceeded that of the pristine TPU film. FTIR analysis showed variations in the -NH₂, C=O, C-O, and C-O-C bands, confirming structural evolution within both hard and soft segments. In summary, UV aging of TPU involves a complex interplay among chain scission, degradation of soft segments, rearrangement of hard segments, evolution of hydrogen bonds, and radical-induced crosslinking. Crucially, the crosslinked network formed during aging plays a pivotal role in determining the macroscopic structural, thermal, and mechanical properties of the polymer. Full article

This work investigates the incorporation of sewage sludge-derived biochar (BC) into a recycled poly(ethylene terephthalate) (rPET) matrix at loadings ranging from 0.5 to 5% wt. in order to develop sustainable nanocomposite materials. The materials were comprehensively characterized using complementary structural, thermal, and morphological techniques to evaluate the effect of BC on the properties of the recycled polymer. XRD, DSC, and PLM analyses demonstrated that BC acts as a heterogeneous nucleating agent, without significantly altering the final crystalline fraction of rPET, while SEM observations confirmed the homogeneous dispersion of particles within the matrix. TGA and Py–GC/MS further indicated that BC moderates thermal degradation, reducing the relative formation of low-molecular-weight degradation products and promoting the retention of larger terephthalate-containing fragments. Accelerated UV irradiation experiments further demonstrated the protective role of BC against photo-induced degradation. Intrinsic viscosity (IV) measurements showed that BC-containing nanocomposites exhibited a smaller molecular-weight reduction after UV exposure compared to neat rPET, indicating reduced chain scission, while complementary DSC analyses confirmed improved preservation of thermal transitions after aging. Overall, sewage sludge-derived biochar is demonstrated to be a promising multifunctional additive for rPET, acting both as a nucleating agent and a UV stabilizer. This approach provides an alternative route for the valorization of two waste streams, contributing to enhanced materials in a circular economy framework. Full article

Hydraulic fracturing enhances productivity in low-permeability reservoirs. The introduction of nanomodified gels for hydraulic fracturing has raised the need to revise traditional approaches to their breakdown, as nanoparticles significantly change the kinetics and mechanisms of degradation. In this paper, for the first time, a systematic experimental study of the effects of chemical breakers on the rheological properties of nanomodified guar gels has been conducted. Two commercial oxidative breakers were used, which generate free radicals and cleave the guar polymer backbone, reducing viscosity. The effect of breaker concentration (0–1.82 wt%), as well as the concentration, size, and morphology of nanoparticles on gel breaking, has been studied. Guar gum was used as a gelling agent, and spherical SiO₂ and Al₂O₃ nanoparticles, as well as aluminum oxide nanofibers (ANFs), were used as additives. An increase in breaker concentration accelerates gel breaking. For instance, at 0.68 wt% breaker, complete degradation occurs in about 3 h, whereas at 1.82 wt% it takes only about half an hour, with the viscosity dropping to 30 mPa·s. While nano-additives can either slow down or accelerate degradation depending on their type, size, and concentration, the addition of 0.4 wt% ANFs prolong the degradation time to more than two hours even at the highest breaker concentration. These effects are attributed to the competition between polymer chain scission by free radicals and the formation of physical crosslinks mediated by nanoparticles. The results demonstrate the possibility of purposefully controlling the kinetics of breaking of nanomodified gels for hydraulic fracturing by optimally selecting the breaker composition and nano-additive parameters. Full article

Polystyrene (PS), particularly expanded polystyrene (EPS), is an environmentally significant commodity polymer that contributes substantially to secondary microplastic and nanoplastic pollution through environmental weathering and fragmentation. During aging, PS undergoes nano-scale physicochemical transformations, including chain scission, surface oxidation, and the formation of oxygen-containing functional groups, which profoundly influence its environmental fate, microbial colonization, and biodegradation behavior. Conventional remediation technologies remain energy-intensive and often fail to achieve complete mineralization, highlighting the need for sustainable and integrated remediation strategies. Recent studies have demonstrated that diverse microorganisms, including Pseudomonas, Rhodococcus, Bacillus, and Exiguobacterium, can colonize PS surfaces and initiate oxidative depolymerization through extracellular biofilm formation and oxidative enzymes such as styrene monooxygenase, laccases, and peroxidases. In parallel, insect-based systems, particularly Tenebrio molitor and Zophobas morio, provide unique biological platforms in which gut microbiota facilitate partial PS degradation and mineralization through synergistic host–microbe interactions. This review critically integrates recent advances in nano-scale PS transformation, microbial colonization, oxidative enzymatic pathways, insect gut-mediated biodegradation, and advanced analytical techniques used to characterize degradation processes. Emphasis is placed on nano–bio interactions and emerging nanotechnology-enabled remediation strategies, including engineered microbial consortia, biofilm-based bioreactors, and nanomaterial-assisted treatment systems. Finally, current limitations and future research priorities are discussed, including degradation kinetics, byproduct toxicity, standardized evaluation methods, and the integration of biological and nanomaterial-based approaches for scalable PS microplastic remediation. Full article

Fiber-reinforced polymer (FRP) composites are extensively used in aerospace, civil engineering, and defense applications because of their low density, high specific strength, corrosion resistance, and structural design flexibility. However, prolonged exposure to hygrothermal conditions, ultraviolet (UV) radiation, and thermo-oxidative environments can progressively damage these materials, leading to mechanical degradation and shortened service life. This review examines environmental aging in FRP composites at the levels of the polymer matrix, fiber/matrix interface, and reinforcing fibers. Representative predictive models, finite element methods, and experimental characterization techniques are summarized, together with the evolution of mechanical properties under different aging conditions. Hygrothermal degradation is mainly associated with moisture diffusion, matrix swelling, and interfacial debonding, whereas UV and thermo-oxidative aging are largely governed by photo-oxidation and thermally activated free-radical reactions. These processes may induce chain scission, crosslinking, matrix embrittlement, and interface damage. Under coupled environmental exposure, degradation is not simply additive because moisture transport, oxidation kinetics, and failure pathways may interact. Future research should emphasize multiscale characterization, anti-aging modification, interface engineering, protective coatings, and reliability-oriented lifetime prediction. Full article

Two bio-based insulating oils (BHOs) with average carbon chain lengths of approximately 18 and 22 were investigated as short- and long-chain BHOs. By constructing an oil-paper composite insulation system, the generation law of characteristic gases in the two systems was studied by partial discharge experiments. Based on the ReaxFF reaction molecular dynamics simulation under electrothermal coupling stress, the cracking path, cracking rate, evolution of oxygen-containing small molecules, and generation path of characteristic gases of cellulose polymer were revealed. Both systems produced H₂, CH₄, C₂H₂, C₂H₄, C₂H₆, CO, and CO₂, with CO₂ dominant and C₂H₆ least abundant. The short-chain BHO generated markedly higher amounts of H₂, CO, C₂H₂, and C₂H₄ than the long-chain BHO; after 15 min, its H₂ and CO concentrations were about 3.4- and 2.1-times those in the long-chain system, respectively. ReaxFF simulations showed that cellulose degradation in the short-chain BHO followed stepwise chain scission and continuous decarbonylation, favoring CO and unsaturated gas precursors. In contrast, cellulose chains disappeared faster in the long-chain BHO, producing more oxygen-containing organic fragments and C₁-C₅ oxygenated molecules and a higher small-molecule conversion ratio. Characteristic gas pathway analysis revealed that all seven gases could be generated from cellulose pyrolysis intermediates, and different oil environments primarily influenced gas generation behavior by altering the evolution pathways of these intermediates. These findings, at the molecular scale, elucidate the impact of BHO environments on the degradation mechanism of cellulose polymers, providing a theoretical basis for the condition assessment and design of environmentally friendly oil-paper insulation systems. Full article

Hydrolyzed polyacrylamide stabilized oil-in-water emulsions are highly persistent because the polymer strengthens both continuous-phase rheology and the oil–water interfacial film, making demulsification difficult in polymer-flooding produced liquids. Here, an hydrolyzed polyacrylamide degrading bacterium, Delftia lacustris EPDB-8, was isolated, and its ability to destabilize hydrolyzed polyacrylamide-containing emulsions was investigated from molecular, bulk rheological, and interfacial perspectives. EPDB-8 effectively degraded HPAM, causing marked reductions in total organic carbon, total nitrogen, absolute zeta potential, and polymer molecular weight, with an approximately 63-fold decrease after 7 days. SEM, FT-IR, and GPC analyses showed that biodegradation proceeded through deamidation and random chain scission, collapsing the polymer network and generating low-molecular-weight fragments. Driven by bacterial hydrolyzed polyacrylamide degradation, these structural alterations disrupted the viscoelastic composite interfacial film formed by hydrolyzed polyacrylamide and indigenous surface-active species, directly causing emulsion stabilization to shift from polymer-assisted viscous and steric protection to a less effective asphaltene-dominated interfacial structure and thereby accelerating droplet aggregation, coalescence, and phase separation. Although bacterial cells exerted a transient particle-assisted interfacial effect, long-term emulsion stability remained governed by polymer integrity. This study establishes a mechanistic link between hydrolyzed polyacrylamide biodegradation and the rheological and interfacial evolution governing emulsion breakdown, providing a cost-effective and environmentally benign biological strategy for demulsification and treatment of polymer-flooding produced water. These findings offer practical guidance for the design of microbial-based produced-water treatment systems and contribute to the sustainable management of oilfield wastewater generated during enhanced oil recovery operations. Full article

Plastics are indispensable to modern life, yet pose a double-edged sword as their escalating production threatens human health and ecosystems. This urgent reality drives intensive efforts to develop recycling technologies that convert waste plastics into valuable feedstocks. Herein, we develop an efficient organocatalytic strategy for the depolymerization and closed-loop chemical recycling of poly(butylene succinate) (PBS). The strong organic base TBD demonstrated the highest catalytic activity for the methanolysis depolymerization of PBS, achieving a yield of 93.1% under mild conditions (100 °C, 2 h). GC and MS analyses identified dimethyl succinate (DMS) and 1,4-butanediol (1,4-BDO) as the major products. Investigation into the depolymerization behavior and mechanism revealed that the process proceeds via random chain scission, facilitated by a dual hydrogen-bonding activation mechanism mediated by TBD. Closed-loop chemical recycling was achieved by repolymerizing the recovered monomers into PBS. The reproduced polymer exhibited properties comparable to commercial virgin PBS. Moreover, this strategy could be extended to other commercial polyester systems, establishing an eco-friendly and viable pathway for sustainable polymer recycling. Full article

This study highlights the strong ability of a new bacterial strain, Hafnia paralvei UUNT_MP29, isolated from the gastrointestinal tract (GIT) of common carp (Cyprinus carpio), to break down polystyrene (PS). As an omnivorous bottom feeder, C. carpio is constantly exposed to microplastics, creating a unique environment that favors the evolution of specialized microbiota capable of degrading polymers. Genomic analysis of the isolate identified key homologs involved in xenobiotic breakdown, including alcohol dehydrogenase (Adh), 3-hydroxybutyrate dehydrogenase (HDH), and a small glutamine-rich tetratricopeptide repeat-containing protein (SGTA), showing a strong metabolic system for processing long-chain hydrocarbons. Growth experiments showed the strain quickly adapted, reaching maximum cell density and forming mature biofilms by Day 16. Gravimetric analysis confirmed that H. paralvei UUNT_MP29 uses PS as its primary carbon source, with a significant weight loss of 16.76% over 16 days. Kinetic modeling indicated the degradation follows first-order kinetics (R² = 0.9243) with a high degradation rate constant (k) of 0.2078 day⁻¹. Surface analyses using FTIR and SEM confirmed extensive oxidative changes, as evidenced by the rising Carbonyl Index and surface erosion. TGA also showed reduced thermal stability of the treated polymer, suggesting microbial chain scission. These findings demonstrate the strong degradative ability of H. paralvei UUNT_MP29 and highlight the GIT of plastic-exposed aquatic animals as a promising area for discovering powerful biocatalysts for microplastic cleanup. Full article