Search Results (2,261)

The development of biodegradable polymer composites from renewable resources is important for reducing dependence on petroleum-based plastics and improving the sustainability of short-life-cycle products. However, poly(butylene succinate) (PBS)/poly(lactic acid) (PLA) blends are generally immiscible, and the reinforcing effect of alkali-treated hemp stem fiber (HSF) on their mechanical, thermal, rheological, morphological, and biodegradation behavior remains insufficiently understood. This study investigates PBS/PLA biocomposites prepared at fixed blend ratios of 90/10 and 80/20 wt.% and reinforced with 5–20 phr alkali-treated HSF. Hemp stem fibers are treated using 5 wt.% NaOH, dried, sieved, and compounded with PBS/PLA blends in an internal mixer at 190 °C and 50 rpm for 15 min, and fabricated by hot compression molding at 190 °C for 13 min. The incorporation of HSF improves composite stiffness, with the highest Young’s modulus of 306 MPa observed for the 80/20/15 composition, representing a 71% increase over neat PBS. The maximum flexural strength reaches 48 MPa for 90/10/20, while the highest flexural modulus reaches 1377 MPa for 80/20/20, representing improvements of 21% and 77%, respectively. In contrast, tensile stress at break and elongation at break generally decrease with HSF incorporation because localized fiber agglomeration, incomplete matrix wetting, and interfacial gaps limit effective stress transfer, particularly at higher HSF loadings. The MFR exhibits composition-dependent, non-monotonic behavior. The addition of PLA initially increases the MFR relative to neat PBS, whereas higher HSF loadings generally reduce the MFR due to restricted polymer chain mobility and increased resistance to melt flow. FT-IR results indicate no strong chemical interactions among PBS, PLA, and HSF, while DSC shows nearly unchanged melting temperatures but composition-dependent changes in PBS crystallinity and crystallization behavior. FESEM confirms a phase-separated PBS/PLA morphology with embedded HSF. Soil burial tests show increased weight loss with higher HSF content and exposure time, confirming enhanced biodegradation. Full article

Bacterial cellulose (BC) combines high stiffness, low density and a unique three-dimensional fibrillar network, making it a promising bio-based reinforcement for polymer composites. In this study, BC pellicles were cultivated under static, room-temperature conditions in Hestrin–Schramm medium, and purified, freeze-dried and processed into BC/epoxy laminates using wet compression moulding. The processing route was designed to minimise destruction of the native BC architecture, enabling a feasibility assessment of integrating a native BC network into an industrially relevant wet compression moulding process. Specimens were produced according to DIN EN ISO 527-4 at a fixed fibre mass fraction of approximately 8.8 wt%. Scanning electron microscopy (SEM) imaging revealed a predominantly in-plane oriented, channel-like BC network; however, the composites also exhibited inhomogeneities, including dry areas, voids, and resin-rich regions. Mechanical testing demonstrated an increase in Young’s modulus from 2.95 GPa for neat epoxy to approximately 4 GPa for BC-reinforced laminates, whereas the tensile strength of BC-reinforced laminates (approximately 25 MPa) remained below that of the neat epoxy reference. Hence, stiffness was improved while strength remained limited due to process-induced material defects and the low fibre content. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements indicated no substantial differences in thermal degradation behaviour across the investigated processing temperatures. Taken together, these results demonstrate the feasibility of processing BC networks into epoxy laminates and identify impregnation inhomogeneity as a key limitation at this early stage. The work further stresses the need for improved control of BC morphology, drying, and impregnation, as well as improved fibre–matrix adhesion in future studies in order to better harness the structural potential of bacterial cellulose in fibre-reinforced polymer composites. Full article

The manufacturing of drug-loaded filaments aimed for fused deposition modeling (FDM) three-dimensional printing (3DP) is still an important challenge because the filament mechanical profile and printing performance depend on both formulation and process-related factors. This study investigated the impact of extrusion technology on the mechanical properties and printability of paracetamol-loaded polyvinyl alcohol filaments with variable compositions. Filaments with compositions according to a full-factorial design were processed by single-screw extrusion (SSE) and twin-screw extrusion (TSE). Mechanical properties were assessed using the 3-point bending test and stiffness test. The thermal behavior of the components was evaluated through differential scanning calorimetry (DSC), while printability was evaluated through feeding and printing tests. Both formulation factors affected mechanical performance. High paracetamol content generally reduces stiffness and flexural resistance while increasing deformation capacity, suggesting a secondary plasticizing effect in the studied concentration range. Mannitol exhibited limited plasticizing efficiency, with flexibility decreasing at high ratios. DSC indicated partial crystallinity after extrusion, with TSE showing lower residual melting enthalpies than SSE. TSE filaments provided higher model reproducibility, broader mechanical ranges, and higher printability scores. This study shows that formulation effects depended strongly on extrusion technology and highlights TSE as a more robust platform for producing printable pharmaceutical filaments. Full article

Problem statement: Contaminated mixed plastic waste—bearing metallic, paper, cardboard and organic residues—remains largely excluded from mechanical recycling because conventional routes require a costly, water- and energy-intensive washing–drying pretreatment. Research gap: No published study combines a fully dry, washing-free valorisation route for such waste with certified mechanical characterisation and a quantified CO₂ mass balance that explicitly credits elimination of the washing–drying stage. Methodology: This study presents DMP (Downcycled Mixed Plastic), a patented (OSIM, Romania) dry valorisation process based on continuous single-screw extrusion (D = 150 mm, L/D = 17.3), characterised through differential scanning calorimetry (DSC), certified mechanical/thermal testing at accredited Romanian laboratories, Weber-number dispersion analysis, and a process-parameter sensitivity study. Key findings: The composite exhibits certified mechanical properties (tensile strength 9.22 MPa, elongation at break 112.8%, compressive strength 14.5 MPa); composition–property analysis across four batches shows that increasing the PP weight fraction from 20 to 28 wt% raises tensile strength by 8.3% while reducing elongation by 5.2%; a computed Weber number (We = 166.7 ≫ We_crit) is consistent with fine PP-phase dispersion within the PE matrix; the sensitivity study confirms statistically robust structure–property relationships (R² = 0.93–0.98); and the CO₂ mass balance establishes a net avoidance of 3.150 t CO₂ eq per tonne of waste processed relative to conventional wet recycling. Significance: dry, washing-free processing is a technically promising pathway for valorising plastic waste streams currently considered non-recyclable, potentially reducing production cost by 60–70% relative to wet recycling, pending additional characterisation identified as priorities for future work. Full article

This study tailors titanium nitride (TiN)-reinforced RT70 HC nanocomposite phase change materials (PCMs) for medium-temperature thermal energy storage. TiN nanoparticles were incorporated into commercial RT70 HC at 0.1–2.0 wt.% by a two-stage method combining sodium dodecyl sulfate, magnetic stirring, and ultrasonication, and characterized by FT-IR, XRD, SEM-EDX, elemental mapping, DSC, thermal conductivity, Cp, TGA, and 1000-cycle tests. FT-IR and XRD confirmed the physical integration of TiN into RT70 HC without new chemical bonds or secondary phases, and SEM-EDX showed a concentration-dependent dispersion. The phase change temperatures were largely preserved. The latent heat varied non-monotonically with TiN content, increasing at low loadings (0.1–0.5 wt.%) and decreasing at higher loadings. Because each composition was prepared as a single batch and measured on small specimens, the low-loading latent-heat increase (up to about 9%) is indicative rather than statistically proven and may fall within the subsampling variance. The 0.5 wt.% sample reached the highest values of 306/296 J/g in the first cycle and 286/268 J/g after 1000 cycles. The thermal conductivity increased with TiN content, reaching a maximum enhancement of about 24.09% in the liquid phase (0.1785 to 0.2215 W/(m·K) at 80 °C) and 35.7% in the solid phase at 2.0 wt.%, whereas the specific heat capacity was lower at higher loadings, an indicative trade-off given the single-run measurement uncertainty. TGA showed degradation onset temperatures above 240 °C, a wide safety margin relative to the ~72 °C working range. Overall, the 0.1–0.5 wt.% formulations offered the most balanced thermal performance for medium-temperature applications. Full article

The growing demand for sustainable protein sources is driving the development of marine by-product utilization. Mussel byssus, which is currently discarded during mussel processing, could be used to produce collagen-derived biomaterials. This study tested the hypothesis that ultrasound-assisted extraction could improve collagen recovery by comparing its efficiency with that of conventional pepsin-assisted extraction. The latter is time-consuming and inefficient. While conventional pepsin-assisted extraction achieved a higher collagen-derived material recovery yield (10.7%) than ultrasound-assisted extraction (5.1%), ultrasound reduced the extraction time from 72 h to just two hours. Fourier transform infrared spectroscopy (FTIR) confirmed that the characteristic amide bands were preserved in the collagen-derived material extracted using both methods. Differential scanning calorimetry (DSC) revealed thermal transitions at 59 °C for pepsin-assisted extracts and 57 °C for ultrasound-assisted extracts, indicating comparable thermal stability. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed predominantly low-molecular-weight protein fragments (<20 kDa), suggesting the presence of collagen-derived peptides rather than intact native collagen. Overall, ultrasound-assisted extraction preserved the structural and thermal characteristics of the extracted material while drastically reducing processing time. This highlights its potential as a rapid, environmentally friendly and sustainable technology for the valorization of mussel byssus within a circular bioeconomy. 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

The chemically modified ammonium lignosulfonate (ALS) powders with carboxylic acids such as, oleic (OA) and lactic acid (LA) and γ-butyrolactone (BL) under dielectric barrier plasma discharge (DBD) have been characterized by average molecular weight and particle size determinations, morphology examination by optical and electronic microscopy (SEM), the study of the thermal properties by thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), differential thermal analysis (DTA) and antioxidant activity tests by DPPH method. The thermal characterization of the modified lignosulfonates reveals their improved thermal stability comparatively with ALS. It has been established that the obtained microparticles are aggregates of particles, covered by modified polymer and exhibit a particular behavior depending on the chemical structure of the used modifier, leading to multifunctional active lignin-based products with better homogeneity. By surface modification, the antioxidant capacity of modified lignosulfonate powders has been maintained. Full article

This study presents the development of a one-part phosphate-activated geopolymer foam based on fayalite flotation residue from the copper industry. The solid activator consisted of triple superphosphate, enabling a dry-mix binder that requires only water addition prior to use. Foamed materials were characterized by XRD, FTIR, Mössbauer spectroscopy, DSC-TG, hot-stage microscopy, SEM-EDX and physical and mechanical testing. The foaming of the geopolymer reduced the densities between 0.753 and 2.15 g/cm³, relative porosities up to 73.6%, and compressive strengths ranging from 1.4 to 28.8 MPa. The foamed geopolymer maintained dimensional stability up to about 1000 °C. The thermal conductivity coefficient measured on large-sized specimen blocks was 0.099 W/mK at a density of 0.753 g/cm³. These results demonstrate that fayalite slag can be effectively utilized as a precursor for sustainable geopolymer foams combining low thermal conductivity, high thermal stability, and the utilization of industrial by-products. Full article

Polylactic acid (PLA) remains poorly mineralized under mesophilic conditions relevant to home and decentralized composting. This study assessed whether bioaugmentation with Amycolatopsis orientalis, protein-based biostimulation with skimmed milk powder, or their combined application could enhance the mineralization of compression-molded amorphous PLA fragments at 28 °C in activated vermiculite. Closed respirometric bioreactors were monitored for 90 days, and the PLA mineralization extent was calculated from the cumulative CO₂ evolution after correction using treatment-specific blanks. The recovered PLA fragments were further analyzed by FTIR-ATR and DSC to provide complementary physicochemical monitoring. The final mineralization remained low, reaching 1.19 ± 1.88% for bioaugmentation, 3.49 ± 1.82% for biostimulation, and 8.75 ± 4.31% for the combined treatment. The combined treatment gave the highest mean value, which was significantly higher than bioaugmentation alone, but the individual biological replicates followed heterogeneous trajectories. In particular, BABS-3 reached 13.19% mineralization, indicating that higher responses can occur at the individual bioreactor level, although they were not consistently reproduced. FTIR-ATR and DSC revealed treatment- and replicate-dependent physicochemical changes but did not provide evidence of extensive bulk PLA transformation. These results contrast those of previous reports of higher PLA mineralization under warmer, mature compost conditions, emphasizing the complexity of the combined influence of temperature and matrix. Overall, the tested strategies were insufficient to achieve effective home compostability of PLA at 28 °C. Full article

The firing of traditional gray pottery relies on complex physicochemical reactions governing its color, dimensional accuracy, and structural stability. Unclear kiln-transformation mechanisms restrict standardized and digital production of this Chinese intangible cultural heritage. Herein, direct ink writing (DIW) was used to fabricate Hejin gray pottery green bodies from local ternary raw materials. Thermodynamic calculations, TG–DTG/DSC, XRD, XRF, and atmosphere-controlled firing tests were combined to reveal coupled phase evolution and reduction color-forming mechanisms during sintering. Two interrelated kiln-transformation processes were identified. First, sequential mineral reconstruction occurs at four critical temperatures: free water loss at 119.8 °C, two-stage dehydroxylation of hydrous silicates at 270.5 °C and 767.9 °C, and CaCO₃ decomposition at 547.9 °C. Uneven shrinkage and gas release at these temperatures induce cracking, blistering, and deformation of printed bodies. Micron-sized CaCO₃ (equivalent radius ≈ 1.31 μm) exhibits high surface energy and significantly reduces its decomposition temperature, consistent with experimental observations. Second, reducing atmospheres trigger competitive phase formation. Distinct from the conventional Fe₂O₃ → Fe₃O₄ → FeO reduction pathway, Fe oxides preferentially react with abundant Al₂O₃ to form thermodynamically stable FeAl₂O₄ spinel, yielding uniform celadon-gray tones. The final color is nearly independent of 20–90 vol% CO, and air-isolated cooling below 600 °C is mandatory to prevent secondary oxidation and reddening. This work establishes a thermodynamic framework for DIW-printed Hejin gray pottery kiln transformation, clarifies microscale defect and color-evolution mechanisms, and offers theoretical guidance for atmosphere-controlled firing and digital mass production of heritage ceramics. Full article

The development of transparent multifunctional coatings capable of combining optical properties with mechanical durability remains a significant challenge in advanced materials engineering. In this study, novel hybrid coatings based on a poly(vinyl butyral)/epoxy resin (PVB/epoxy) matrix reinforced with tungsten disulfide (WS₂) nanostructures were developed and examined for potential application in camouflage protection of glass surfaces. Camouflage aims to reduce the detectability of an object by minimizing the optical contrast between the object and its surrounding environment. For transparent substrates such as glass, this objective is particularly demanding because the transparency must be preserved while reducing unwanted surface reflection and optical signatures over relevant spectral ranges. For this purpose, in this research two types of nanostructures were investigated: fullerene-like nanoparticles (IF-WS₂) and inorganic nanotubes (INT-WS₂). The coatings were fabricated via ultrasonically assisted solution dispersion followed by casting over the glass plates and Teflon molds, and solvent evaporation. Structural, thermal, optical, and mechanical properties were systematically evaluated using SEM, FTIR, DSC, UV-Vis-NIR spectroscopy, gloss measurements, hardness testing, and cavitation wear resistance analysis. The incorporation of WS₂ nanostructures led to improved mechanical performance, with increased hardness and enhanced resistance to cavitation-induced wear. Optical characterization showed moderate reductions in reflectance and controlled transmittance in the visible and near-infrared regions, while overall transparency was maintained. The results indicate that WS₂ nanostructures contribute to both light scattering and absorption, leading to reduced specular reflection and improved optical masking potential. The findings demonstrate that hybrid PVB/epoxy/WS₂ coatings offer a promising approach for designing transparent, mechanically resistant coatings with tunable optical properties, with potential applications in protective glass systems and advanced functional surfaces. Full article

Circulating fluidized bed (CFB) fly ash exhibits immense potential as a supplementary cementitious material, yet its application is limited by volumetric instability related to delayed ettringite formation. This study investigates the effect of grinding and ultrafine grinding on hydration behavior, microstructure, and long-term volumetric stability of CFB fly ash–cement composites using isothermal calorimetry, XRD, SEM-EDS, TG-DSC, and MIP. Results show that increasing fineness shortens the induction period and advances the second hydration peak by ~6 h. The cumulative heat release of the UCFA system reaches 95.2% of plain cement (85 h). Ultrafine grinding improves hydration activity and reduces total pore volume by 7.32% compared with cement and 22.18% compared with RCFA, leading to denser microstructures and higher compressive strength. Mechanistically, grinding modifies the outer sulfate-bearing layer, accelerating sulfate dissolution and early ettringite formation, while promoting CaO exposure and pozzolanic reactions. Long-term tests up to 730 days confirm that UCFA significantly reduces linear expansion, indicating improved volumetric stability. These results demonstrate that ultrafine grinding simultaneously enhances hydration reactivity and long-term stability, providing a feasible route for high-value utilization of CFB fly ash in cementitious systems. Full article

To evaluate the durability of desert sand concrete (DSC) in a semi-buried saline-alkali soil environment, this study examined DSC with a 30% desert sand replacement rate, using ordinary concrete (OC) as a control. A 180-day mixed salt attack test was conducted under continuous axial compressive loads (0, 30% f_c, and 50% f_c) and semi-immersion in a mixed salt solution (5% NaCl + 5% Na₂SO₄). Macroscopic and microscopic tests were conducted to reveal the damage evolution patterns of DSC, and a life prediction model was established using a nonlinear Wiener process. The results indicate that after 180 days of semi-immersion, under identical exposure media and load levels, DSC exhibited overall better durability retention compared with OC. A 30% f_c load helped reduce pore connectivity in the DSC, suppressing the development of harmful and highly harmful pores and delaying performance degradation, whereas a 50% f_c load promoted microcrack propagation and pore connectivity, accelerating degradation. Under mixed salt semi-immersion conditions, the “wick effect” caused distinct regional damage in DSC; compared with the corresponding soaking section, the adsorption section showed 3.84–5.17% lower K_n values for compressive strength and a 25.57–42.52% higher proportion of harmful and highly harmful pores. The developed nonlinear Wiener model can reasonably characterize the relative degradation process of DSC under different exposure conditions, and the predicted trends are in good agreement with the results of macro- and micro-scale analyses. Full article

This study comprehensively investigates the thermal and mechanical degradation behavior of molded glass-fiber-reinforced plastic (GFRP) grating composites subjected to temperatures ranging from 80 °C to 320 °C. Three types of industrially produced GFRP gratings—open-type (OG), thin closed-skin (CG), and thick closed-skin (TCG)—were evaluated using mechanical, microstructural, chemical, and crystallographic analyses. Three-point bending tests revealed that TCG-type specimens exhibited superior thermal resistance, experiencing only a 43.9% loss in strength at 320 °C, whereas OG-type specimens showed significant resin degradation, fiber–matrix decomposition, and microcrack formation at temperatures above 200 °C. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed significant resin degradation, fiber–matrix decomposition, and microcrack formation. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) confirmed substantial mass loss and structural disintegration at temperatures above 200 °C. Dynamic Mechanical Analysis (DMA) results revealed that the glass transition temperature (Tg) occurred at approximately 115–120 °C. The second-order regression model developed to estimate flexural strength under increasing temperature provided high accuracy (R² > 0.99) for all grating types. It should be noted that this investigation focuses on the short-term thermo-mechanical response under fundamental flexural loading to provide an accurate baseline for preliminary engineering design. The findings emphasize that the effect of temperature should be considered a critical parameter in the structural design of GFRP systems, especially in industrial environments with temperatures above 120 °C. Accordingly, tables for material selection and load-carrying capacity should be recalibrated to account for short-term temperature effects. Full article