Search Results (252)

The demands of the green economy necessitate modern polymer materials that are not only environmentally friendly but also durable and capable of long service life. Bio-based polylactide (PLA) polyesters have gained significant traction in various industrial markets; however, their application in specialized sectors is hindered by high brittleness. This study extensively examines the effects of 1–5% of synthetically obtained tetracyclosiloxane (CS) and octaspherosilicate (OSS) derivatives with methacrylate (MA) and trimethoxysilyl (TMOS) groups as functional modifiers for PLA. The research provides a detailed characterization of PLA/CS and PLA/OSS materials, including a comparative analysis of mechanical properties such as tensile, flexural, and dynamic resistance. Notably, incorporating 5% CS-2MA-2TMOS into PLA resulted in a remarkable 104% increase in impact resistance. The study further evaluates the influence of these modifications on thermal properties (DSC, TGA), heat deflection temperature (HDT), and surface character (WCA). The miscibility between the organosilicon additives and PLA was assessed using oscillatory rheometry and SEM-EDS analysis. The melt-rheology analysis explained the mechanisms behind the interaction between the CS and OSS additives with the PLA matrix, highlighting their lubricating effects on the melt flow behavior. The study was complemented by XRD structural analysis and verification of the structure of PLA-based materials by optical microscopy and SEM analysis, demonstrating a plasticizing effect and uniform distribution of the modifiers. The findings strongly suggest that, even at low concentrations, organosilicon additives serve as effective impact modifiers for PLA. Full article

The increasing accumulation of plastic waste—especially from packaging and post-consumer sources—calls for the development of sustainable recycling strategies. Due to the challenges associated with sorting mixed waste, directly processing waste streams offers a practical approach. Polyethylene terephthalate (PET) and high-density polyethylene (HDPE) are common consumer plastics, but they are difficult to recycle together due to immiscibility and degradation. In mixed waste, recycled HDPE (r-HDPE) often contaminates the recycled PET (r-PET) stream. Additive manufacturing (AM) offers a promising solution to upcycle these mixed polymers into functional products with minimal waste. This study investigates the processing and characterization of r-PET/r-HDPE blends for AM, focusing on the role of compatibilizers in enhancing their properties. Blends were melt-compounded using a twin-screw extruder to improve dispersion, followed by direct pellet-based 3D printing. A compatibilizer (0–7 php) was incorporated to improve miscibility. Rheological testing showed that the 5 php compatibilizer optimized viscosity and elasticity, ensuring smoother extrusion. Thermal analysis revealed a 30 °C increase in crystallization temperature and a shift in decomposition temperature from 370 °C to 400 °C, indicating improved thermal stability. Mechanical testing showed a tensile strength of 35 MPa and 17% elongation at break at optimal loading. Scanning electron microscopy (SEM) confirmed reduced phase separation and improved morphology. This work demonstrates that properly compatibilized r-PET/r-HDPE blends enable sustainable 3D printing without requiring polymer separation. The results highlight a viable path for the conversion of plastic waste into high-value, customizable components, contributing to landfill reduction and advancing circular economy practices in polymer manufacturing. Full article

In recent years, coffee waste by-products have been incorporated into polymer blends to reduce environmental pollution. In this study, coffee parchment (CP) was incorporated into biodegradable polylactic acid (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) polymer blends to prepare ribbons through the extrusion process. Extracted green coffee bean oil (CO) was used as a plasticizer, and CP was used as a filler with and without functionalization. A solution of chitosan nanoparticles (ChNp) as a coating was applied to the ribbons. For the raw material, proximal analysis of the CP showed cellulose and lignin contents of 53.09 ± 3.42% and 23.60 ± 1.74%, respectively. The morphology of the blends was observed via scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) showed an increase in the ribbons’ thermal stability with the functionalization. The results of differential scanning calorimetry (DSC) revealed better miscibility for the functionalized samples. The mechanical properties showed that with CP incorporation into the blends and with the ChNp coating, the Young’s modulus and the tensile strength decreased with no significant changes in the elongation at break. This work highlights the potential of reusing different by-products from the coffee industry, such as coffee oil from green beans and coffee parchment as a filler, and incorporating them into PLA PBAT biodegradable polymer blend ribbons with a nanostructured antimicrobial coating based on chitosan for future applications in food packaging. Full article

Currently, the development of oil reservoirs with high water cut faces numerous challenges, including poor economic efficiency, difficulties in residual oil recovery, and a lack of effective development technologies. In light of these issues, this paper conducts research on gas drive development during the high water cut stage in middle–high permeability reservoirs and introduces an innovative technical approach for air thermal miscible flooding. In this study, the Enhanced Oil Recovery (EOR) mechanism and the dynamic characteristics of thermal miscible flooding were investigated through laboratory experiments and numerical simulations. The N₂ and CO₂ flooding experiments indicate that gas channeling is likely to occur when miscible flooding cannot be achieved, due to the smaller gas–water mobility ratio compared to the gas–oil mobility ratio during the high water cut stage. Consequently, the enhanced recovery efficiency of N₂ and CO₂ flooding is limited. The experiment on air thermal miscible flooding demonstrates that under conditions of high water content, this method can form a stable high-temperature thermal oxidation front. The high temperature, generated by the thermal oxidation front, promotes the miscibility of flue gas and crude oil, effectively inhibiting gas flow, preventing gas channeling, and significantly enhancing oil recovery. Numerical simulations indicate that the production stage of air hot miscible flooding in reservoirs with middle–high permeability and high water cut can be divided into three phases: pressurization and drainage response, high efficiency and stable production with a low air–oil ratio, and low efficiency production with a high air–oil ratio. These phases can enable efficient development during the high water cut stage in medium to high permeability reservoirs, with the theoretical EOR range expected to exceed 30%. Full article

This study develops highly flexible, biodegradable polymer blends using bio-based polyhydroxyalkanoate (PHA) polymers for Fused Deposition Modeling (FDM) 3D printing. A Design of Experiment (DoE) approach optimized blend compositions by varying crystallinity levels of three PHAs, processed via twin-screw extrusion. Rheological analysis revealed that PHA blends exhibited 30–50% lower viscosity than PLA at low shear rates, ensuring improved processability. Tensile testing confirmed favorable mechanical properties, with elongation at break exceeding 2000%, significantly surpassing PLA (29%). Differential scanning calorimetry (DSC) indicated partial miscibility and crystallinity reductions of up to 50%, influencing printability. Optimized 3D printing parameters demonstrated minimal warping for blends with crystallinity below 18%, ensuring high-dimensional stability. During home composting tests, PHA blends showed significant degradation within two months, whereas PLA remained intact. Scanning electron microscopy (SEM) confirmed microbial degradation. Cytotoxicity tests demonstrated that the blends were non-toxic, supporting applications in tissue engineering. These findings highlight the potential of PHA-based blends as sustainable, high-performance materials for biomedical, packaging, and environmental applications. Full article

The shock absorbers in the landing gear absorb and dissipate a significant amount of kinetic energy generated from impacts during the landing and taxiing phases to ensure the stability and safety of the aircraft. The nitrogen–oil binary system is a commonly used energy absorption medium in these shock absorbers. Nevertheless, the interplay of interfacial mass transfer dynamics, microscopic dissolution behavior, and pressure drop in the aviation hydraulic oil–N₂ system under landing conditions necessitates further elucidation. Thus, we investigated the interfacial mass transfer characteristics of the oil–gas mixing process using molecular dynamics (MD) for analyzing the dissolution mechanism of N₂ in the aviation hydraulic oil system. The results show that as system pressure and temperature increase, the degree of oil–gas mixing intensifies. Under conditions of 373 K, 35 MPa and 433 K, 20 MPa, the diffusion coefficient, interfacial thickness, and system energy reach their maximum values. An increase in system pressure facilitates the occurrence of oil–gas mixing until the interface disappears at the minimum miscibility pressure (MMP), with the obtained MMP value being 107 MPa. Finally, the solubility of N₂ molecules in aviation hydraulic oil under different conditions was statistically analyzed, which is identified as the root cause of the pressure drop in the shock absorber’s gas chamber. This study innovatively applies molecular dynamics simulations to unveil, for the first time, the dissolution mechanism of N₂ in aviation hydraulic oil at the molecular scale, overcoming experimental limitations in observing extreme pressure–temperature conditions. This research elucidates the behavior of aviation hydraulic oil and N₂ under different thermodynamic conditions, making it easier to capture the patterns of phenomena that are difficult to observe in extreme environments. The research findings not only enhance the microscopic understanding of oil–gas mixing within the shock absorber but also provide valuable guidance for optimizing energy dissipation efficiency, improving damping characteristics, and enhancing safety in aircraft landing gear systems. Full article

The inherent brittleness of bio-based poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) significantly restricts its industrial applications despite its industrial compostability. Blending with elastomeric polymers addresses mechanical limitations; however, interfacial incompatibility compromises miscibility as our previous work established. Herein, we investigate coffee oil epoxide (COE) as a bio-based plasticizer for PHBV/natural rubber (NR) blends in sustainable packaging applications. COE, derived from spent coffee grounds, was incorporated into PHBV/NR/peroxide/coagent composites via twin-screw extrusion. FTIR spectroscopy with chemometric analysis confirmed successful COE incorporation (intensified CH₂ stretching: 2847, 2920 cm⁻¹; reduced crystallinity), with PCA and PLS-DA accounting for 67.9% and 54.4% of spectral variance. COE incorporation improved optical properties (7.73% increased lightness; 21.9% reduced yellowness). Rheological characterization through Cole–Cole and Han plots demonstrated enhanced phase compatibility in the PHBV/NR/COE blends. Mechanical testing showed characteristic reductions in flexural properties: strength decreased by 16.5% and modulus by 36.8%. Dynamic mechanical analysis revealed PHBV/NR/COE blends exhibited a single relaxation transition at 32 °C versus distinct glass transition temperatures in PHBV/NR blends. Tan δ deconvolution confirmed the transformation from bimodal distribution to a single broadened peak, indicating enhanced interfacial interactions and improved miscibility. These findings demonstrated COE’s potential as a sustainable additive for biodegradable PHBV-based packaging while valorizing food waste. Full article

Active food packaging is a significant trend in recent years in the food industry. This paper presents the results of studies on selected properties of a mixture of polylactide and polycaprolactone containing 1 or 5 wt.% of tannic acid. The function of tannic acid was to improve the miscibility of the polymers used and to give the obtained composition antibacterial properties. Studies were carried out on color and transparency, microscopic analysis, water vapor permeability, mass flow rate, static tensile properties, impact strength, dynamic mechanical analysis, thermogravimetry and differential scanning calorimetry. The obtained results did not confirm the compatibilizing effect of tannic acid, because the obtained mechanical properties were slightly worse than those of materials without the addition of this compound. However, the obtained mixture was characterized as having biocidal properties against two strains of Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538P). Antibacterial properties together with acceptable processing, mechanical and thermal properties indicate that the presented polymer material may be a potential material for the production of active food packaging. Full article

To address the limitations of poly (lactic acid) (PLA), it was blended with poly (methyl methacrylate) (PMMA) as a toughening component, using MgO nanoparticles (NPs, 0.075–0.15 wt%) as a catalyst. SEM pictures confirmed the good miscibility of the blends. Mechanical tests showed a slight decrease in elastic modulus and tensile strength for the PLA/PMMA125 sample containing 0.125% MgO. Yet, elongation at break rose by over 60% and impact strength increased by over 400% compared to pure PLA. Also, MgO facilitated the shifting of the glass transition temperature (T_g) of both polymers in DSC curves. Additionally, the absence of cold crystallization in PLA, coupled with reductions in its melting temperature (T_m) and crystallinity, were identified as critical factors contributing to improved miscibility within the reactive blend. Melt flow index (MFI) evaluation indicated a decrease in viscosity, while water contact angle measurements revealed an increase in polar groups on the surfaces of the MgO-containing samples. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the effective distribution and dispersion of NPs throughout the blend, along with a significant decrease in crystallinity. Moreover, DFT calculations were performed to better understand the role of MgO in the reaction. The findings offered key insights into the reaction mechanism, confirming that MgO plays a crucial role in facilitating the transesterification between PLA and PMMA. These findings underscore the enhanced performance of exchange reactions between the active groups of both polymers in the presence of MgO, leading to the formation of PLA-PMMA copolymers with superior miscibility and mechanical properties. Finally, a cell culture assay confirmed the blend’s non-toxicity, showing its versatile potential. Full article

In this paper, the geometric effect on flow structure and mixing performance of two miscible fluids (deionized water and glycerol) in a planetary centrifugal mixer (PCM) during the spin-up is numerically evaluated, using the OpenFOAM interMixingFoam solver. Six different aspect ratios, specifically 0.5, 1, 1.25, 1.5, 2, and 2.5, are considered. The flow structure in each geometric configuration is illustrated by the liquid interface and vorticity isosurface represented by the Q criterion, while the mixing performance is evaluated in terms of a mixing index $MI$. As the aspect ratio increases from small to large, $MI$ first increases and then decreases. The peak $MI$ at the end of spin-up reaches 0.196 for the aspect ratio of 1.25, rather than the other five aspect ratios in our study. The mechanism analysis shows that under an aspect ratio of 1.25, the vortex structure is most violently dissipated, the interface collapse degree is the largest, and the low-velocity region volume is the smallest, which enhances the chaotic convection mixing. Full article

Immiscible Al–Sn–Cu alloys may offer attractive properties, attaining superior tribological and mechanical properties when Sn-rich soft particles are homogeneously distributed in the reinforced Al–Cu matrix. In this paper, the solidifications of both Al-10 wt.% Cu-10 wt.% Sn and Al-10 wt.% Cu-20 wt.% Sn alloys were investigated to analyze the successive stages that occur during the controlled cooling of these alloys, from the initial formation of the α-Al dendritic array to the final eutectic reaction. In particular, we focus on the liquid-phase demixing occurring during the solidification path, which leads to the formation of Sn droplets in the melt through a nucleation-growth process. Horizontal directional solidifications were performed on thin samples in a Bridgman-type furnace, with in situ and real-time observations using X-ray radioscopy. Two different behaviors have been found concerning liquid separation: for the low-Sn-content alloy, liquid demixing occurs in one single step, whereas for the high-Sn-content alloy, it is a two-step process, with first the nucleation of a few small Sn droplets followed by a sudden formation of a large amount of wide Sn droplets. The possible causes of these different behaviors are discussed in relation to the literature, namely, either a switch from immiscible to miscible liquids or a transition from the binodal region to the spinodal region. Full article

CO₂ flooding technology for tight oil reservoirs not only effectively addresses the challenge of low recovery rates, but also facilitates geological CO₂ sequestration, thereby achieving the dual objective of enhanced CO₂ utilization and secure storage. However, in the development of continental sedimentary tight oil reservoirs, the high content of heavy hydrocarbons in crude oil leads to an elevated minimum miscibility pressure (MMP) between crude oil and CO₂, thereby limiting the process to non-miscible flooding. Conventional physical and chemical methods, although effective in reducing MMP, are often associated with high costs, environmental concerns, and limited efficacy. To address these challenges, we propose a novel approach utilizing petroleum hydrocarbon-degrading bacteria (PHDB) to biodegrade heavy hydrocarbons in crude oil. This method alters the composition of crude oil, thereby lowering the MMP during CO₂ flooding, facilitating the transition from non-miscible to miscible flooding, and enhancing oil recovery. Results demonstrated that, after 7 days of cultivation, the selected PHDB achieved a degradation efficiency of 56.4% in crude oil, significantly reducing the heavy hydrocarbon content. The relative content of light-saturated hydrocarbons increased by 15.6%, and the carbon atom molar percentage in crude oil decreased from C8 to C6. Following the biodegradation process, the MMP of the lightened crude oil was reduced by 20.9%. Core flood experiments indicated that CO₂ flooding enhanced by PHDB improved oil recovery by 17.7% compared to conventional CO₂ flooding. This research provides a novel technical approach for the green and cost-effective development of tight oil reservoirs with CO₂ immiscible flooding. Full article

This study examines the effects of mastication time and the addition of a plasticizer (acetyl tributyl citrate (ATBC)) on the properties of non-vulcanized polylactic acid/natural rubber (PLA/NR) blends using a factorial design, along with the impact of changing the weight ratio of the blends. The results reveal the formation of plasticized PLA (P-PLA)-based thermoplastics with enhanced ductility. ATBC functions as both a PLA plasticizer and a compatibilizer in the binary PLA/NR system. However, improving compatibility requires the exclusive use of masticated NR with an appropriate mastication time (60 min) before blending. Optimal properties are achieved at a P-PLA/NR weight ratio of 90/10, maximizing the impact strength (~35.40 J/m) and toughness (~7.21 × 10⁶ MJ/m³). However, higher NR contents lead to reduced mechanical performance due to poor interfacial bonding. Thermal analysis reveals superior miscibility and dispersion in blends with a lower NR content (10 wt%), while the addition of plasticizers and NR leads to a decrease in the glass transition temperature (T_g) of the blends. The results suggest potential applications for developing biodegradable products with enhanced flexibility and improved low-temperature performance. The incorporation of ATBC can enhance material properties without relying on conventional synthetic compatibilizers. Full article

Novel biobased double crystalline poly(butylene succinate)-b-poly(butylene 2,5-thiophenedicarboxylate) (PBS-b-PBTh) multiblock copolyesters with excellent thermal and mechanical properties were prepared from two hydroxyl-terminated PBS-diol and PBTh-diol prepolymers via a chain extension reaction. Both PBS and PBTh segments were semicrystalline, with the aliphatic PBS segment being the soft segment while the aromatic PBTh segment was the hard segment. In the case of PBS-b-PBTh, the two segments were partially miscible in the amorphous region; moreover, the melting temperature of each segment still remained very high compared with that of each homopolyester PBS and PBTh. The melt crystallization behavior of both segments was enhanced in the case of PBS-b-PBTh, which was attributed to different mechanisms. The crystal structure study revealed that both segments crystallized separately and showed the characteristic diffraction peaks, respectively. Compared with that of PBS, PBS-b-PBTh displayed a significant increase in the elongation at break while still maintaining a relatively high break strength. This research provides some new insights to synthesize biobased polyesters with excellent thermal and mechanical properties, which should be interesting from a sustainable viewpoint. Full article

The conventional near-infrared laser transmission welding (LTW) process for joining dissimilar transparent polymers is limited by the need to incorporate optical absorbents, which compromises joint performance and raises biocompatibility concerns. To address these issues, this study proposed a surface modification technique using femtosecond laser ablation prior to the welding process. Experiments involved 520 nm femtosecond laser ablation of transparent polymers, followed by LTW of dissimilar transparent polymers using an 808 nm laser, with subsequent characterization and mechanical property evaluations. A maximum joint strength of 13.65 MPa was achieved. A comprehensive investigation was conducted into the physical and chemical mechanisms through which laser ablation improved the welding performance of dissimilar transparent polymers. The results demonstrated that laser ablation generated microstructures that serve as substitutes for optical absorbents while also facilitating the formation of numerous oxygen-containing functional groups. These enhancements improve miscibility and bonding performance between dissimilar polymers, enabling absorbent-free welding between ablated polycarbonate (PC) and polystyrene (PS). This work confirms both the feasibility and potential application of this process for direct LTW of dissimilar transparent polymers. Full article