ABSTRACT In this work, polylactic acid (PLA) based nanocomposites containing bimetallic nanoparticle systems were made using the injection molding method to compare the antimicrobial behavior of alloyed nanoparticles and those physically mixed to be used in biomedical and environmental applications under similar processing and testing conditions. In particular, Ag–Cu alloy, Cu–Ni alloy, Ag–Cu mixture, and Cu–Ni mixture nanoparticles were introduced in PLA at a loading of 3 wt.% metal nanoparticles and 97 wt.% PLA. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to analyze structural, morphological, and thermal properties of the composites. The results of SEM/EDS and XRD analyses revealed more homogeneous dispersion of the nanoparticles and more phase‐separated crystalline structures in the mixture systems, while the alloy systems had higher agglomeration and a single intermediate diffraction peak corresponding to alloy formation; the thermal stability of the mixtures was quite retained with degradation starting from around 320°C–360°C, and the glass transition temperature between 56.5°C and 59.5°C. The time‐kill assay was used to determine antimicrobial activity against standard laboratory Gram‐positive and Gram‐negative bacterial strains, which cause healthcare‐associated infections. Time‐dependent antibacterial activity was observed for all composites. The four nanocomposites achieved mean log 10 reductions of 0.19 to 0.86 in the first 5 to 20 min, and 0.70 to 1.16 after 1 h, whereas the PLA control reduced by 0.29 log 10 after 1 h. PLA + Cu–Ni alloy showed the maximum strain‐specific activity against Enterococcus faecalis , reaching 1.99‐log 10 reduction (98.98%) after 1 h. All composite formulations resulted in near complete killing (> 99.9%) of four out of the six strains after 8 h and six out of six strains after 24 h. Alloyed systems showed an initial strong antibacterial activity, while the physically mixed systems showed similar long‐term bactericidal activity. These results suggest that the metallurgical integration is likely attributed to increased initial antimicrobial kinetics, and the sustained release of ions over time ensures long‐term killing, resulting in a shift from a kinetics‐dominated to a diffusion‐dominated antimicrobial response over time. The results show that these bimetallic nanoparticle PLA composites can be used as tunable antibacterial materials for healthcare, packaging, and other hygienic applications, but additional safety and durability testing is needed.
ABSTRACT Bio‐based materials that valorize waste streams while enabling resource conservation are central to advancing circular and sustainable environmental solutions. This study reports the development of ionically crosslinked biochar‐encapsulated hydrogels (Bio‐H) as sustainable adsorbents for the removal of heavy metals from contaminated water systems. Cyanidioschyzon merolae‐derived biochar, produced by hydrothermal liquefaction of biomass was incorporated into calcium‐crosslinked sodium alginate using a two‐step gelation process, creating a multifunctional, biodegradable composite. Swelling behavior demonstrated that biochar incorporation significantly reduced the initial contraction observed in pristine alginate hydrogels and enabled continuous, monotonic swelling, achieving equilibrium swelling ratios of 1.16 within 7 h, substantially faster than pristine systems. The mechanical integrity of the Bio‐H was assessed by dynamic mechanical analysis (DMA). The storage modulus (G′) exceeded the loss modulus (G″) across the entire 0.1–100 Hz range with no crossover, reaching a plateau of about 372 kPa, confirming a stable, elastically dominant crosslinked network. Scanning electron microscopy revealed an open macroporous network that became textured with particulate deposits after adsorption, with EDS confirming Cu and Fe uptake. Batch adsorption experiments showed that maximum adsorption capacities were achieved at pH 4 and 298 K. The maximum equilibrium adsorption capacity for Cu2+ was 136 mg/g, whereas for Fe3+, the adsorption capacity was observed to be 1.25 mg/g. The M5 model suggests that the adsorption of both metals proceeds through a physical multilayer mechanism, which involves heterogeneous binding sites and sequential stacking of metal ions. The Bio‐H still removed the metal ions after the 3rd cycle of adsorption‐regeneration.
ABSTRACT Energy losses due to friction and wear are a major challenge for the energy efficiency and sustainability of mechanical systems, motivating the development of green tribology strategies. This review provides a critical and integrative analysis of biopolymers derived from renewable resources, including cellulose, chitin, alginate, and starch as constituents of lubricants and tribological coatings. Contrary to previous reviews, this work introduces a mechanistic classification that connects biopolymer chemical properties such as charge, hydrophilicity, and molar mass to main lubrication mechanisms, including interfacial adsorption, hydrated lubrication, viscoelastic dissipation, and biopolymer‐nanoparticle hybrid systems. A quantitative synthesis of the literature data shows that modified biopolymers and nanocomposites consistently achieve better tribological performance than their unmodified counterparts. Wear reductions exceeding 50% and 0.05 as a coefficient of friction are reported for systems based on chitosan, modified cellulose, and zwitterionic hydrogels reinforced with nanofillers under moderate to high loads. Chemical modification strategies and controlled nanoparticle incorporation have also been reported to improve thermo‐oxidative stability, depending on whether stability is assessed via viscosity retention, oxidation‐induction time, or chemical integrity during high‐temperature aging (typically in the ~120°C–150°C range). This review identifies the most promising biopolymer–modification–nanoparticle combinations, highlights the current limitations related to the heterogeneity of experimental parameters, and proposes guidelines for the rational design of high‐performance, sustainable biolubricants aimed at reducing the energy and environmental footprint of tribological systems.
ABSTRACT Thermoresponsive shape memory polymers derived from segmented thermoplastic polyurethanes (TPUs) present a compelling integration of processability, elasticity, and programmable deformation. This study involves the incorporation of octamethyl polyhedral oligomeric silsesquioxane (OMP) into an aliphatic polyether‐based TPU through solution casting followed by melt blending to create mechanically robust shape‐memory nanocomposites. This study systematically examined the effect of OMP loading (1–4 wt.%) on microphase morphology, short‐range ordering, thermomechanical behavior, and shape‐memory performance. Microscopic studies and X‐ray diffraction studies indicate that low to intermediate OMP contents facilitate homogeneous dispersion and inhibit hard‐segment aggregation, whereas higher loadings lead to OMP–OMP self‐association and the formation of rigid OMP‐rich domains. DSC and DMA indicate that OMP influences segmental dynamics through modifications in hydrogen bonding, heat‐capacity increments, and elevation of storage modulus, thus adjusting elastic energy storage and dissipation. The nanocomposite with 2 wt.% OMP demonstrated the optimal balance of tensile strength, extensibility, and viscoelastic contrast, achieving a peak shape recovery of 97.0% with values decreasing to 80.2% over five repeated cycles alongside significant shape fixity of 94.0%–84.0%. Cyclic thermomechanical tests demonstrated enhanced durability and recovery retention for this composition, while thermally triggered recovery experiments revealed rapid and complete recovery, underscoring its responsiveness to practical stimuli. This study demonstrates that melt‐blended TPU/OMP nanocomposites function as effective thermally programmable shape‐memory materials and clarifies the structure–property relationships that influence their performance.
ABSTRACT The development of sustainable, high‐performance materials has intensified the demand for natural fiber‐reinforced polymer (NFRP) composites. However, the inherent limitations of natural fibers, such as low interfacial bonding and high moisture absorption, necessitate advanced hybridization and filler modification. This study investigates the mechanical, physical, and morphological characteristics of a novel five‐layer hybrid composite. The system utilizes a symmetrical Jute/JUCO/Glass/JUCO/Jute stacking sequence reinforced with an epoxy matrix and synergistically enhanced by copper oxide (CuO) and titanium dioxide (TiO 2 ) microparticles. Fabricated via hand layup, the composites were evaluated at filler loadings of 1, 2, and 3 wt%. Results indicate that CuO at 3 wt.% yielded up to approximately 63.68% increase in tensile strength as compared to the control sample, while TiO 2 reached peak flexural strength and modulus at 42.15 MPa and 2.4 GPa, respectively. Impact strength trends suggest an increase of 121% with CuO and 85.25% with TiO 2 . Physical testing revealed that porosity and water absorption were reduced when microparticles were added, with TiO 2 providing better moisture resistance, as determined by the water absorption test. Improved fiber‐matrix interfacial adhesion was found in both micro‐filler systems by scanning electron microscopy analysis. These findings indicate that microfiller incorporation can enhance selected mechanical and physical properties of hybrid natural fiber composites. Specifically, the TiO 2 ‐reinforced hybrid composite (T‐3) demonstrated properties comparable to automotive interior components, suggesting potential for non‐structural or semi‐structural applications. However, the scope of the present study is limited to short‐term mechanical and physical evaluation, and additional investigations, particularly on fatigue performance, thermal stability, and long‐term environmental durability, are necessary to substantiate their suitability for demanding structural applications.
ABSTRACT Robotic rotational molding represents a major advancement over conventional techniques by integrating automation, electric heating, and advanced cooling. This process enables cost‐effective production of stress‐free hollow polymer parts with improved quality. A key development is the Robomould system, which uses a robotic arm to control mold movement and electrically heated molds instead of a traditional oven, allowing for superior control over the layer‐thickness distribution. Although the Robomould concept targets a wide range of product geometries, the experimental validation in this work focuses on a single axisymmetric 82 L liner without internal features. Typically, a rock‐and‐roll movement is applied, but current practice still relies on trial and error to define suitable movement and heating parameters, often causing long set‐up phases. To address this, a simple and computationally inexpensive movement model is proposed to estimate thickness distribution for given parameters. The model considers only product geometry and movement, neglecting thermal effects and dynamic powder effects. A volumetric mesh of the product is used to simulate powder distribution, and the powder–mold contact time of each element is translated into local thickness distribution estimation. Despite its simplicity, experimental validation demonstrates strong predictive value, supporting faster process set‐up by reducing reliance on trial and error.
ABSTRACT High‐performance amorphous thermoplastics such as polyetherimide ( PEI ) are widely used in aerospace applications; however, thick‐walled sections are prone to internal void formation due to volumetric shrinkage and premature gate solidification. In this work, the influence of processing variables on void mitigation in thick‐walled PEI components was investigated using an industrially constrained experimental design. Analysis of variance showed that thermal parameters dominated defect variation, with cooling time and mold temperature contributing 50.4% and 30.15%, respectively. Linear regression identified gate freeze time ( GFT ) as a practical process indicator of pressure‐transmission efficiency, exhibiting a strong negative correlation with the maximum void diameter ( r = −0.964, R 2 = 0.930). A regression‐derived threshold of 5.61 s corresponded to the aerospace specification limit of 0.75 mm, and a conservative production target of 6.5 s was recommended based on the 95% prediction interval analysis. Under optimized conditions (160°C mold temperature, 40 s cooling time), the process achieved a GFT of 8.0 s and produced no ultrasonically detectable voids (maximum void diameter < 0.1 mm). Scrap rates decreased from 18.7% to 1.1%, reducing manufacturing cost per accepted part. These findings establish GFT as a practical mechanistic indicator for process‐window development in thick‐walled high‐performance thermoplastics.
ABSTRACT The growing demand for environmentally responsible materials has accelerated research into green composites that utilize recycled polymers and waste‐derived fillers. However, balancing mechanical strength, thermal stability, and compatibility among multiple fillers remains a key challenge. This study addresses this by formulating recycled high‐density polyethylene (rHDPE) composites reinforced with wood powder (WP) and calcium carbonate (CaCO3), and modified with ground tyre powder (GTP) and maleic anhydride grafted polyethylene (MAPE). The wood powder serves as a renewable lignocellulosic reinforcement to improve stiffness and reduce material cost, while calcium carbonate acts as an inorganic filler enhancing thermal stability and rigidity. Ground tyre powder is incorporated primarily as a waste valorization strategy to address the environmental challenge of end‐of‐life tyres. MAPE (5 wt%) functions as a compatibilizer to strengthen interfacial bonding between the hydrophilic and hydrophobic phases. Composites containing 0–25 wt% WP were prepared with fixed levels of CaCO3 (5 wt%), GTP (5 wt%), and MAPE (5 wt%) via extrusion and injection molding. The 0 wt% WP formulation serves as an internal baseline (rHDPE +5% MAPE +5% CaCO3 + 5% GTP), not neat rHDPE. Mechanical testing revealed marked increases in tensile strength, stiffness, and modulus with higher WP content, with optimal performance at 25 wt% WP. Elongation at break decreased accordingly, indicating the expected stiffness–ductility trade‐off. Thermogravimetric analysis (TGA) demonstrated notable improvements in char yield attributed to the cumulative contributions of CaCO3 and tyre‐derived residues, while differential scanning calorimetry (DSC) indicated reduced crystallinity. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of constituent materials and showed spectral features consistent with enhanced interfacial compatibility, although covalent bond formation could not be definitively confirmed without complementary techniques (e.g., XPS). The findings demonstrate that combining lignocellulosic and inorganic fillers with recycled polymers and waste rubber yields composites with superior rigidity, strength, and thermal stability. This work provides a foundational formulation and processing protocol for sustainable composite development, while explicitly acknowledging that mechanistic interpretations of interfacial chemistry and filler synergy require further validation through controlled experimental designs and direct morphological/spectroscopic evidence.
ABSTRACT This study investigates the effects of long jute (LJ) fiber reinforcement on the mechanical, thermal and sound transmission loss (STL) properties of polypropylene (PP)‐based biocomposites. Long fiber thermoplastics (LFT) are increasingly used in various industries, including automotive applications, due to their superior mechanical performance and lightweight characteristics. The biocomposites were fabricated using an LFT‐G production line, incorporating different weight fractions of LJ fibers (20, 30, and 40 wt.%) into PP. The sound insulation properties of the composites were analyzed through STL measurements. Compared to neat PP, PP‐40LJ exhibited an STL increase of approximately 45% at 100 Hz and 55% at 1000 Hz, indicating improved frequency‐dependent sound attenuation with increasing jute fiber content. Mechanical characterization was performed through tensile, flexural, and impact tests, while morphological analysis was conducted via scanning electron microscopy (SEM). Thermomechanical performance was significantly enhanced, as evidenced by an increase in heat distortion temperature (HDT) from 57.9°C to 126.6°C and Vicat softening temperature (VST) up to 104.4°C, indicating a higher service temperature for the composites. These findings highlight the potential of LJ fiber‐reinforced PP composites for lightweight applications requiring enhanced sound insulation and thermal properties.
ABSTRACT In this study, graphene oxide (GO)‐modified poly (phenylene oxide, PPO) anion exchange membranes (F/GO) were developed for application in anion exchange membrane electrolyzers (AEMELs). The incorporation of GO enhanced membrane hydration, ion‐exchange capacity, and hydroxide‐ion conductivity, resulting in an ~15% increase in current density at 2.0 V and 80°C (0.551 A/cm2) compared with the pristine membrane (0.480 A/cm−2). The F/GO membranes also showed enhanced hydrogen production rates and an HHV‐based energy efficiency of 76% at 0.5 A/cm2 and 80°C. These results underscore the potential for F/GO membranes in scalable AEMEL applications. Mechanical and alkaline stability tests confirmed robustness under harsh conditions. These findings demonstrate that the incorporation of GO provides a simple, scalable, and potentially lower‐cost modification strategy compared with highly engineered polymer architectures, while also improving overall electrolyzer performance, highlighting the potential of GO‐modified membranes for practical hydrogen production in AEMEL systems.
ABSTRACT In this study, chaste berry oil and red clover extract were combined for the first time in nanoemulsion and nanofiber form. To that end, it was first demonstrated that nanoemulsions could be prepared separately using chaste berry oil and red clover extract, followed by the production of red clover extract‐in‐chaste berry oil nanoemulsions. All components were added individually and in combination to prepare pectin‐stabilized emulsions, yielding the following results: Regardless of the type of nanoemulsion, the use of pectin led to a substantial increase in droplet size (e.g., from 113–233 to 287–845 nm red clover extract‐in‐chaste berry oil). Pectin/herbal component nanofibers were able to be obtained when a feed rate of 0.5 mL/h was used under an applied voltage of 15 kV and the needle‐collector distance was set to 21 cm. While the fiber diameter of pure pectin nanofibers was approximately 400 nm, the addition of herbal components with/without surfactant to the solutions increased the fiber diameters (713–823 nm for red clover extract‐in‐chaste berry oil). In addition, nanofibers with large fiber diameters exhibited generally big pore sizes.
ABSTRACT This study examines the influence of processing strategy on the thermal and mechanical properties of polyetherimide (PEI)‐carbon nanotube‐expanded graphite composites. Two melt compounding approaches, single‐step (SS) and two‐step (TS) were evaluated at identical filler loadings (15 wt% EG, 0.5 wt% CNT, plus additives). Both approaches enhanced the in‐plane thermal conductivity relative to neat PEI (k0 = 0.22 W/m K). The SS approach achieved 5.75 ± 0.5 W/m K, approximately 20% higher than TS (4.8 ± 0.5 W/m K), attributed to greater graphite exfoliation and improved formation of conductive pathways. However, TS better preserved mechanical properties. These findings highlight the trade‐off between thermal performance and mechanical strength, underscoring the importance of processing strategies for optimizing multifunctional PEI hybrid composites.
ABSTRACT Growing interest in sustainable engineering materials has accelerated the development of natural fiber‐reinforced polymer composites as alternatives to synthetic fiber systems. This study fabricated and characterized epoxy‐based composites reinforced with palm‐derived fibers in two laminate configurations prepared by hand lay‐up: (S1) date palm mesh/date palm bark fiber/date palm mesh and (S2) date palm mesh/palmyra palm husk fiber/date palm mesh. Mechanical performance was evaluated through tensile, flexural, and Charpy impact testing, while thermal conductivity was measured to assess heat‐transfer behavior; microstructural and structural characterization was performed using scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The S1 laminate exhibited higher tensile strength (16.3 MPa) and elongation at break (13.4%) than S2 (8.0 MPa and 6.2%, respectively), and also showed greater impact energy absorption (0.95 N m for S1 vs. 0.77 N m for S2). Thermal conductivity differed markedly between the laminates, with S1 showing a higher conductivity (0.95 W/m K) and S2 exhibiting lower conductivity (0.303 W/m K), indicating improved insulating behavior for the husk‐fiber composite. XRD patterns indicated semi‐crystalline characteristics in both composites, with S1 showing a stronger crystalline contribution (higher diffraction intensity), consistent with a larger fraction of ordered cellulose domains in the reinforcement. SEM observations further revealed improved fiber–matrix wetting and fewer voids in S1 compared with S2, supporting more efficient load transfer and reduced defect‐driven failure. Overall, the results demonstrate that palm‐based reinforcements can yield lightweight epoxy composites with tunable mechanical and thermal performance depending on fiber type and morphology.
ABSTRACT This study analyzes the effect of MgO, Al2O3, and TiO2 metal oxide fillers on the physico‐mechanical and thermal behavior of kenaf/carbon fiber‐reinforced epoxy hybrid composites. Pb3O4‐treated kenaf fibers were combined with carbon fiber mats to create a kenaf–carbon–kenaf (KCK) layered system, fabricated using the hand lay‐up method. Metal oxide fillers were added at concentrations of 1% and 2% to examine their effects on mechanical and physical properties. The tensile test results revealed that the 2% MgO delivered the highest strength of 93.74 MPa, surpassing the control sample (91.3 MPa) and also outperforming the Al2O3 and TiO2 incorporated sample. Flexural strength reached the maximum of 128.28 MPa with 2% of MgO, which is 41.98% higher than that of the control sample (90.35 MPa). The maximum impact strength was obtained at 2% Al2O3 at 56.4 KJ/m2, a 37.46% increase from the control sample (41.03 KJ/m2). In terms of moisture resistance, 2% TiO2 demonstrated the best performance, showing the lowest water absorption. Additionally, the inclusion of metal oxide fillers improved the thermal properties. The higher diffusivity of 2% TiO2 (0.198 mm2/s) and MgO (0.191 mm2/s) with lower volumetric specific heat (1.24 MJ/m3·K) indicates rapid heat transfer, whereas the lower diffusivity of Al2O3 (0.147 mm2/s) and the control (0.116 mm2/s) with higher volume specific heat favors insulation performance. Al2O3 at 2% provides high thermal conductivity while maintaining moderate heat retention. Morphological analysis revealed that 2 wt.% MgO incorporated samples had good fiber‐matrix adhesion, but increased Al2O3 and TiO2 loadings had voids and agglomeration.
ABSTRACT As firefighting efforts increase daily, the use of fire‐resistant materials is also on the rise. However, those materials sometimes create other problems. The discovery that halogenated fire retardants are toxic is one example. Another issue is that inorganic minerals used to provide fire resistance can degrade some mechanical properties in polymer composites. This study aims to prevent the deterioration in mechanical properties caused by the high amount used of huntite and hydromagnesite minerals. In this context, polypropylene‐based composites were developed using huntite‐hydromagnesite, calcite, zeolite, and an intumescent flame retardant. Seventeen different formulations were prepared by twin‐screw extrusion and hot pressing, and then their thermal, mechanical, and flame‐retardant properties were characterized. It was concluded that flame retardancy, as assessed by the UL94 test, reached a V0 rating with only 40% huntite‐hydromagnesite, compared to the conventional 60% load with 10%–20% calcite, zeolite, and intumescent flame retardant. LOI values exceeded 29%, demonstrating strong flame retardant performance. Furthermore, as the main objective of this study, it was observed that tensile strength increased from 23.6 ± SD MPa for HH‐only composites to 25.7 ± SD MPa for hybrid formulations, indicating partial recovery relative to HH‐filled systems. All mechanical properties remained inferior to neat polypropylene.
ABSTRACT Hybrid fiber‐reinforced polymer composites combining natural and synthetic reinforcements offer a promising route toward lightweight and sustainable structural materials. In this study, carbon fiber–palm tree fiber reinforced epoxy hybrid composites were fabricated using a hand lay‐up technique with a symmetric sandwich‐type stacking sequence, where carbon fiber layers were placed on the outer surfaces and palm tree fibers formed the core. Mechanical performance was evaluated through tensile, flexural, and impact tests, while microstructural characteristics and chemical interactions were analyzed using scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. The tensile test results showed tensile strengths ranging from 62.5 to 81.1 MPa, with a maximum Young's modulus of 3.2 GPa and tensile strain values between 3.2% and 3.5%, suggesting possible load sharing between constituents. Flexural testing revealed flexural strengths between 207.3 and 311.0 MPa and flexural moduli ranging from 21.2 to 36.35 GPa, demonstrating the dominant load‐bearing role of the carbon fiber outer layers under bending. Impact testing showed energy absorption values between 1.1 and 2.2 N.m, with average impact energy of 1.47 N.m, which may be associated with the presence of palm fiber layers. SEM analysis revealed mixed‐mode fracture features that are consistent with the observed mechanical behavior. FTIR analysis indicated the presence of characteristic functional groups suggesting chemical compatibility between constituents. Overall, the results demonstrate that carbon fiber–palm tree fiber hybrid composites fabricated via hand lay‐up exhibit mechanically viable performance levels for non‐critical lightweight structural applications, while highlighting the influence of fabrication‐induced variability on structural reliability.
Global plastic production currently exceeds 400 million metric tons annually. Due to the short service life of plastic products, the amount of waste is constantly rising. Recycling this heterogeneous waste is essential; however, the diverse composition of plastic waste presents challenges in reprocessing, easily resulting in polymer blends. This study combined X-ray computed tomography (X-CT) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) to characterize real, unwashed recycled plastic blend. Low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and polyethylene terephthalate (PET) wastes were melt-blended using two different temperatures: 210 degrees C and 270 degrees C, typical for processing of polyolefins and PET, respectively. Unlike studies based on clean laboratory blends, this study quantified PET dispersion and the influence of contaminants and processing temperatures on mechanical properties. The findings revealed that higher processing temperatures resulted in a more uniform structure by reducing PET particle size and void content, but decreased tensile strength and elastic modulus by 7% and 10%, respectively, due to thermomechanical degradation, as evident by a reduction in molecular weight. These findings highlight the challenge of optimizing processing conditions for heterogeneous plastic waste, where structural uniformity and mechanical performance can conflict. Balancing these factors is essential for effective use of recycled materials.
The growing interest in sustainable rubber materials motivates the use of renewable resources for the development of advanced materials. Lignin, valued for its abundance, biodegradability, and mechanical strengths, emerges as a promising alternative filler in rubber composites. This study produced composites using nitrile rubber (NBR) and a 70:30 blend of NBR with carboxylated nitrile rubber (XNBR), each incorporating 40 parts per hundred of rubber (phr) of kraft lignin. Two methods were tested for incorporating lignin: direct addition of 40 phr of lignin powder to the rubbers or compounding using masterbatches of NBR/lignin and XNBR/lignin, each with 130 phr of lignin produced by co-coagulation. Results revealed that NBR/XNBR/lignin composites show thinner, more aligned lignin particles than NBR/lignin composites, with the masterbatch technique further reducing particle size. All lignin-filled rubbers exhibited an increased reaction rate constant of vulcanization, lower covalent crosslink density, and higher ionic crosslink density compared to unfilled rubber. Notably, composites made with lignin masterbatch exhibited a reduced Payne effect, as well as higher tensile and tear strengths, than those made using lignin powder. These findings suggest that incorporating lignin via a masterbatch and blending with XNBR offers a compelling strategy for enhancing the properties of NBR-based rubber composites.
In this study, organometallic complexes were introduced at 0.05 wt% to modify the performance of a 70/30 LLDPE/PP waste blend during a single recycling cycle under high shear. Four complexes (C8-Ti, C8-Zr, C18-Ti, and C18-Zr), based on Titanium (Ti) or Zirconium (Zr) with phosphate esters of different alkyl chain lengths (PC8 or PC18), were incorporated under high-shear mixing, and their effects on structural, thermal, morphological, and mechanical properties were investigated. Sequential processing of the unmodified waste increased PP crystallinity from 16.1% to 42.7% and reduced total crystallinity from 30.4% to 24.5%, indicating progressive phase separation. Upon additive incorporation, total crystallinity further decreased to 27.9% for C18-Ti and 29.3% for C8-Ti, while C18-Zr showed a slight increase to 35.2%, indicating structure-dependent effects on phase packing. T_onset values ranged from 409 degrees C to 444 degrees C across all formulations, indicating essentially unchanged thermal stability. Mechanical testing showed that Charpy impact strength increased by up to 50%, rising from 11.3 to approximately 16.7 kJ/m2 (ISO 179-1), without detrimental effects on tensile properties, as confirmed by statistical analysis (ANOVA). Fracture analysis indicated that Ti-containing samples exhibited more fibrillation, whereas Zr-containing systems showed finer, small-void fracture surfaces. Overall, the findings demonstrate that these organometallic complexes represent a potentially scalable additive strategy for improving mechanical performance in mixed-waste polyolefin streams within a single high-shear recycling cycle.
Enhanced Oil Recovery techniques, particularly chemical flooding, have been used to improve oil displacement efficiency, while the use of synthetic polymers often faces challenges related to ecotoxicity and instability under high temperature and salinity conditions. Biopolymers has been investigated because of their eco-friendly nature, shear-thinning behavior, and structural flexibility. However, native biopolymers still face limitations when exposed to harsh reservoir conditions. To overcome these challenges, the incorporation of nanoparticles has recently been investigated as a strategy to form hybrid biopolymer–nanoparticle systems. These systems have been reported to improve viscosity retention, thermal and salt resistance, wettability alteration, reduction of interfacial tension, and adsorption control, which can increase recovery efficiency. This review highlights recent progress in hybrid biopolymer–nanoparticle systems, focusing on their underlying mechanisms, experimental findings, and prospects for advancing sustainable Enhanced Oil Recovery technologies.
