Search Results (162)

This study investigates the removal of microplastics (MPs) from simulated freshwater, brackish water, and seawater using a novel agglomeration–micro-flotation technique. This method combines particle size enlargement, facilitated by kerosene as a bridging agent, with bubble size reduction through column flotation to enhance the removal rate. Six common MP types—polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC)—were evaluated under varying salinity levels and kerosene dosages. Results showed that increasing kerosene dosage significantly improved removal rates, achieving up to ~99% recovery at 10 µL for low- and medium-density MPs (PP, PE, ABS, and PS), while a higher dosage of 30 µL was required for high-density MPs (PET and PVC). Elevated salinity levels (50–100%) promoted bubble stabilization and reduced coalescence, enhancing particle–bubble collisions and the overall flotation performance. This work addresses a key research gap in flotation-based MP removal under saline conditions and highlights the dual benefits of using kerosene—not only to enhance the removal rate but also to enable energy recovery, as both kerosene and plastics are combustible. The proposed technique presents a promising approach for microplastic remediation in aquatic environments, supporting sustainable water treatment and circular resource utilization. Full article

Most acrylate adhesives do not bond well to low-surface-energy substrates (e.g., polyethylene and polypropylene) due to the weak interaction force between the polar adhesive molecules and the substrate. To enhance the adhesion performance on low-surface-energy substrates and investigate the effects of substrate surface energy, roughness, pressure-sensitive adhesive (PSA) surface energy, viscosity, and modulus on adhesion performance, this study modifies the acrylate adhesive by incorporating a hydrogenated-terminated hydroxylated polybutadiene (HHTPB) structure with a double bond at one end. The results demonstrate an enhancement in the adhesion performance of the modified PSAs on High-Density Polyethylene (HDPE). The 24 h peel strength and loop tack increase to 4.88 N/25 mm and 8.14 N/25 mm at 20 °C, respectively, with the failure modes remaining adhesive failure. However, as the temperature increases, the peel strength decreases. The high-temperature resistance of the adhesive improves. Based on the experimental data, a mathematical model is proposed that incorporates both the wetting area and loss factor to predict peel strength. The influence of these two factors on the peel strength of the PSA is dependent on the application temperature of the adhesive. Full article

The accumulation of plastic waste poses a significant environmental challenge, necessitating sustainable solutions. This study investigates the potential of recycling waste plastics for use in the construction industry, emphasizing their integration into building materials and components. Earlier waste plastic recycling was excessively studied as an ingredient in concrete composites, roads, and other use in research. However, in this study, recycled plastic is assessed for use as a sole material for structural products. Raw plastics, including high-density polyethylene, Low-Density Polyethylene, polypropylene, polyolefin, samicanite, and virgin polyethylene, were analyzed for recycling through mechanical extrusion, and their mechanical properties were analyzed to determine their feasibility for construction applications. In this study, the extrusion process, combined with engineered dyes, was investigated with comprehensive material testing as per the ASTM standards to obtain the properties desired for construction. Advanced characterization techniques, including SEM, FTIR, and TGA, were employed to evaluate the chemical composition, thermal stability, and impurities of these waste plastics collected from municipal waste. A gas emission analysis during extrusion confirmed a minimal environmental impact, validating the sustainability of the recycling process. Municipal waste plastic has a considerable quantum of HDPE, PP, and LDPE, which was considered in this research for recycling for construction products. A total of 140 samples were recycled through extrusion and tested across shear, flexural, tensile, and compression categories: 35 samples each. The results showed that rHDPE and PP had good tensile strength and shear resistance. The findings pave the way for developing cost-effective, durable, and eco-friendly building materials, such as rebars, corrugated sheet, blocks, and other products, contributing to environmental conservation and resource efficiency for the construction Industry. Full article

The increasing demand for sustainable road construction materials necessitates innovative solutions to overcome the challenges of Recycled Asphalt Pavement (RAP), including aged binder brittleness, reduced flexibility, and durability concerns. Waste Plastic Aggregates (WPA) offer a promising alternative; however, their thermal aging behavior and interactions with RAP remain insufficiently understood. This study evaluates the performance of RAP-based asphalt mixtures, incorporating three types of WPA—Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), and Polypropylene (PP)—under three thermal aging conditions: mild (60 °C for 7 days), moderate (80 °C for 14 days), and severe (100 °C for 30 days). The mixtures were designed with 30% RAP content, 10% and 20% WPA by aggregate weight, and SBS-modified binder rejuvenated with 2% and 4% sewage sludge bio-oil by binder weight. It is considered that thermal aging may impact the performance of WPA in RAP mixtures; therefore, this study evaluates the durability and mechanical properties of RAP mixtures incorporating LDPE, HDPE, and PP under varying thermal aging conditions to address these challenges. The results showed that incorporating WPA and bio-oil significantly enhanced the mechanical performance, durability, and sustainability of asphalt mixtures. Marshall Stability increased by 12–23%, with values ranging from 12.6 to 13.2 kN for WPA-enhanced mixtures compared to 12.7 kN for the control. ITS improved by 15–20% in dry conditions (1.34–1.44 MPa) and 12–18% in wet conditions (1.15–1.19 MPa), with TSR values reaching up to 82.64%. Fatigue life was extended by 28–43%, with load cycles increasing from 295,600 for the control to 352,310 for PP mixtures. High-temperature performance showed a 12–18% improvement in softening point (57.3 °C to 61.2 °C) and a 23% increase in rutting resistance, with rut depths decreasing from 7.1 mm for the control to 5.45 mm for PP mixtures after 20,000 passes. These results demonstrate that combining RAP, WPA, and bio-oil produces sustainable asphalt mixtures with superior performance under aging and environmental stressors, offering robust solutions for high-demand applications in modern infrastructure. Full article

This study focuses on the deposition of microplastics (MPs) on urban beaches along the central São Paulo coastline, utilizing advanced methodologies such as remote sensing, GNSS altimetric surveys, µ-Raman spectroscopy, and machine learning (ML) models. MP concentrations ranged from 6 to 35 MPs/m², with the highest densities observed near the Port of Santos, attributed to industrial and port activities. The predominant MP types identified were foams (48.7%), fragments (27.7%), and pellets (23.2%), while fibers were rare (0.4%). Beach slope and orientation were found to facilitate the concentration of MP deposition, particularly for foams and pellets. The study’s ML models showed high predictive accuracy, with Random Forest and Gradient Boosting performing exceptionally well for specific MP categories (pellet, fragment, fiber, foam, and film). Polymer characterization revealed the prevalence of polyethylene, polypropylene, and polystyrene, reflecting sources such as disposable packaging and industrial raw materials. The findings emphasize the need for improved waste management and targeted urban beach cleanups, which currently fail to address smaller MPs effectively. This research highlights the critical role of combining in situ data with predictive models to understand MP dynamics in coastal environments. It provides actionable insights for mitigation strategies and contributes to global efforts aligned with the Sustainable Development Goals, particularly SDG 14, aimed at conserving marine ecosystems and reducing pollution. Full article

In this work, the viscoelastic behavior of high-density polyethylene (HDPE) and polypropylene (PP) was studied through stress relaxation experiments conducted at different strain levels. The main objective was to evaluate classical, fractional, and conformable derivatives to analyze molecular mobility, using statistical methods to identify the most accurate representation of the viscoelastic response. Besides the coefficient of determination (R²), the average absolute deviation (AAD) and mean squared error (MSE) were used as evaluation metrics, along with a multivariate analysis of variance (MANOVA) and the response surface methodology (RSM) to optimize the correspondence between experimental data and model predictions. The findings demonstrate that the spring-pot, Fractional Maxwell (FMM), Fractional Voigt–Kelvin (FVKM), and Kohlrausch–Williams-Watts (KWW) models effectively describe stress relaxation under statistical criteria. However, a joint analysis using RSM revealed that the choice of mathematical model significantly influences the outcomes. The FVKM was identified as the most effective for HDPE, while the KWW model best characterized PP. These results highlight the importance of optimization tools in advancing the characterization of polymer viscoelasticity. The ability to select the most accurate models for HDPE and PP under varying conditions can directly improve the performance and durability of products in critical industrial sectors such as packaging, automotive, and medical devices, where long-term mechanical behavior is crucial. By offering a framework adaptable to other materials and modeling approaches, this work provides valuable insights for optimizing polymer processing, improving product design, and enhancing the reliability of polymer-based components in a range of industrial applications. Full article

This work provides a comprehensive study of a density separation treatment through sucrose solution for the removal of microplastics (MPs) from marine sediments. The theoretical determination of flotation velocities for 1.0 mm diameter spherical MPs with a density of 1.3 g/cm³ at various solution temperatures and sucrose contents was performed. An optimal velocity of 1.03 m/h was observed with a 70% sucrose solution at 50 °C. The validation of theoretical velocities was carried out through experimental tests at optimal operating conditions for polypropylene (PP), high-density polyethylene (HDPE), polylactic acid (PLA), and polyvinyl chloride (PVC) as target MPs. The results showed an experimental floating velocity slightly lower than the theoretical predictions for PP, HDPE, and PLA. PVC, instead, characterized by a higher density than the separation solution, showed a settling velocity 42% lower than the theoretical one. Further tests were performed to assess the solid-to-liquid (S/L) ratio effect on MPs’ separation efficiency. The results showed an optimal S/L of 75 kg/m³ with 80% PVC removal and total PP, HDPE, and PLA removal. Finally, the design and cost optimization of a longitudinal settling tank were proposed for the pilot/real-scale treatment. The observed outcomes provided in-depth details useful for the development of an environmentally sustainable treatment for the preservation of marine areas. Full article

The increasing demand for sustainable construction practices has prompted the exploration of innovative materials, such as waste plastics, to enhance both the environmental and mechanical performance of concrete, particularly for rigid pavements. This review investigates the mechanical properties of concrete incorporating four types of waste plastics—high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), and polypropylene (PP). The primary focus is on how these materials affect key mechanical properties, including compressive strength, tensile strength, and flexural strength. The analysis reveals that HDPE and PP, at optimal levels (5–10%), can enhance flexural and crack resistance, making them suitable for non-structural applications. Conversely, LDPE and PVC tend to reduce both compressive and tensile strengths at higher substitution levels due to poor bonding with cementitious materials. Despite these challenges, incorporating waste plastics into concrete presents significant environmental and economic benefits, including plastic waste reduction and lower reliance on natural aggregates. The review also highlights the need for further research on improving plastic–cement bonding through surface treatments and hybrid mix designs. This study contributes to the growing body of knowledge aimed at promoting the use of waste plastics in concrete, offering insights for the development of sustainable, high-performance construction materials. Full article

Hernia repair is the most common surgical operation applied worldwide. Mesh prostheses are used to support weakened or damaged tissue to decrease the risk of hernia recurrence. However, the patches currently used in clinic applications have significant short-term and long-term risks. This study aimed to design, produce, and characterize a three-layered semi-resorbable composite hernia mesh using the electrospinning technique, where the upper layer (parietal side) was made of non-resorbable polypropylene (PP-Cl) fibers, the partially resorbable middle layer was made of PP-Cl and polycaprolactone (PCL) fibers, and the fully resorbable lower layer (visceral side) was made of H. perforatum oil-loaded polyethylene glycol (PEG) fibers. The extracellular matrix-like fibrous structure of the patches provided low density and high porosity, minimizing the risk of long-term foreign body reactions, and the hydrophilic/hydrophobic character of the surfaces and the detected swelling rates supported biocompatibility. The patches exhibited mechanical properties comparable to commercially available products. Controlled release of therapeutic oil could be achieved from the oil-integrated patches due to the dissolution of PEG in the acute process. In vitro cell culture studies with the L929 mouse fibroblast cell line revealed that the meshes do not have a cytotoxic nor a biomaterial-induced necrotic effect that will induce apoptosis of the cells. The visceral side of the meshes exhibited non-adherence of cell-like structures to the surface due to the dissolution of PEG. The composite hernia patches were concluded to reduce the risk of adhering to internal organs in the hernia area, have the potential to be used in in vivo biomedical applications, and will support the search for an ideal hernia mesh that can be used in the treatment of abdominal hernias. Full article

This study investigates the tensile and flexural properties of self-reinforced polylactic acid (SrPLA) and poly(ethylene terephthalate) (SrPET) for prosthetic socket applications. These self-reinforced polymer (srP) composites utilize both a matrix and reinforcement made from the same material, resulting in an optimal matrix–interface bond that significantly enhances mechanical properties compared to traditional bulk polymers and composites. Prosthetic sockets serve as a critical interface between an amputee’s residuum and the prosthetic components, such as pylons and feet. Conventional socket materials, including monolithic high-density polyethylene and polypropylene, as well as advanced fillers reinforced with thermoset resins, often fall short in strength or affordability, particularly for amputees in low- to middle-income countries. In this study, we employed srP composites with various architectural stitch densities, aiming to achieve superior material properties. The results demonstrate that these materials exhibit higher strength and strain capabilities than many existing prosthetic materials. Notably, the low-density srPET composites achieved a tensile strength of 85.11 MPa and a strain of 19.7%, while high-density srPLA exhibited a failure strength of 36.65 MPa and a strain of 1.4%. Additionally, our findings reveal that the stiffness of both srPLA and srPET increases as the density of the reinforcement decreases. Overall, this study suggests that srP composites represent a viable and sustainable alternative for the manufacturing of prosthetic sockets, offering both enhanced performance and cost-effectiveness. Full article

The phase separation of high-density polyethylene (HDPE)–polypropylene (PP) blends was studied using atomic force microscopy in tapping mode to obtain height and phase images. The results are compared with those from scanning electron microscopy imaging and are connected to the thermomechanical properties of the blends, characterised through differential scanning calorimetry, dynamic mechanical analysis (DMA), and tensile testing. Pure PP, as well as 10:90 and 20:80 weight ratio HDPE–PP blends, showed a homogeneous morphology, but the 25:75 HDPE–PP blends exhibited a sub-micrometre droplet-matrix structure, and the 50:50 HDPE–PP blends displayed a more complex co-continuous nano/microphase-separated structure. These complex phase separation morphologies correlate with the increased loss modulus (viscous properties) of the corresponding blends as measured by DMA, demonstrating the potential for the creation of strong and simultaneously tough, energy-absorbing materials for numerous applications. Full article

Various plastics and biomass wastes, such as polypropylene (PP), low- or high-density polyethylene (LDPE/HDPE), and lignin, have become some of the most concerning wastes nowadays. In this context, this study aimed to investigate the possibility of applying thermochemical processes for the valorization of these materials. The experiments were carried out using a thermogravimetric analyzer on individual plastic and lignin samples and their mixtures at different mass ratios of 1:1, 1:2, 1:3, and 1:4. The gaseous products evolved during the pyrolysis process were analyzed by combined thermogravimetric and Fourier-transform infrared spectroscopy (TG-FTIR) and chromatography-mass spectrometry (Py-GC/MS) to analyze the functional groups and chemical composition of the obtained pyrolysis products. The results showed that the main functional groups of lignin monitored by TG-FTIR were aromatic and aliphatic hydrocarbons, while all plastics showed the same results for hydrocarbons. The investigation confirmed that mixing these types of plastics with lignin at different mass ratios led to increased recovery of higher-value-added products. Py-GC/MS analysis showed that the greatest results of compound recovery were achieved with lignin and LDPE/HDPE mixtures at 600 °C. At this temperature and with a mass ratio of 1:3, the plastic’s radicals enhanced the depolymerization of lignin, encouraging its wider decomposition to hydrocarbons that can be applied for the production of value-added chemicals and bio-based energy. Full article

Oyster farming plays a crucial role in sustainable food production due to its high nutritional value and relatively low environmental impact. However, in a scenario of increasing production, it is necessary to consider the issue of plastic use as a limitation to be addressed. A life cycle assessment (LCA) was conducted on oyster farming in La Spezia (Italy) as a case study, utilizing 1 kg of packaged oysters as the functional unit. Fossil-based plastics and wooden packaging were identified as the primary environmental concerns. To analyze potential strategies for reducing the environmental impact of oyster farming, alternative scenarios were considered wherein fossil-based materials were replaced with bio-based materials. Specifically, this study examined the substitution of the current packaging, consisting of a wooden box and a polypropylene (PP) film, with a fully recyclable PP net. Additionally, polylactic acid (PLA), polyhydroxyalkanoates (PHAs), and bio-based polyethylene terephthalate (Bio-PET) were proposed as alternatives to virgin high-density polyethylene (HDPE) and PP for buoys, oyster bags, and boxes. Among the scenarios analyzed, the sole effective strategy to reduce the impact of plastics on the process is to replace them with PHA. In the other cases, the high energy consumption of their non-optimized production renders them disadvantageous options. However, the assessment must include the effects of degradation that traditional plastics can have in the marine environment, an aspect that potentially renders natural fibers more advantageous. The use of PP net packaging has demonstrated high efficacy in reducing impacts and provides a foundation for considering the need to combine sustainability and marketing with current legislation regarding food packaging. Full article

The natural and laboratory-accelerated weathering of wood–plastic composites (WPCs) based on high-density polyethylene (HDPE) and polypropylene (PP) plastics was investigated in this study. Injection molded samples of WPCs with different loadings of wood fiber ranging from 0 to 36 wt.% of wood were subjected to laboratory-accelerated weathering and natural weathering. The integrity of samples weathered to different extents was tested using a standard tensile test and surface hardness test to investigate the dependence of these properties on the duration of weathering exposure. Tensile data were used to identify the loading of wood fibers in either plastic matrix that afforded superior ultra-violet (UV) stability. Tensile measurements under uniaxial strain yielded average values of tensile strength (TS), low-extension modulus (E), and elongation at break (EB). Both natural weathering outdoors and accelerated weathering in the laboratory showed that the TS and EB decreased while the E increased with the duration of exposure for all samples tested. The change in the average TS of composites with the duration of exposure offers valuable insights. The correlation between the tensile and hardness data for the WPC samples was explored. After naturally weathering at two exposure sites, the hardness of the WPCs was found to decrease between 8% to 12.5%, depending on the composition and exposure location parameters. Furthermore, no marked difference in performance with increasing wood fiber beyond 18 wt.% was observed. WPCs can be a key parameter in environmental sustainability by being used in the building and packaging industries, which reduces carbon emissions and waste generation. Full article

In order to reveal the effects of microplastics (MPs) on the growth and rhizosphere soil environmental effects of wheat (Triticum aestivum L.), three microplastic types (polypropylene MPs (PP-MPs), high-density polyethylene MPs (HDPE-MPs), and polylactic acid MPs (PLA-MPs)), particle sizes (150, 1000, and 4000 μm), and concentrations (0.1, 0.5, and 1 g·kg⁻¹) were selected for a pot experiment under natural environment conditions. The differences in germination rate (GR), germination inhibition rate (GIR), growth characteristics, physicochemical properties, and enzymatic activities of wheat in rhizosphere soil were analyzed using statistical analysis and variance analysis. The results show that the germination rate of wheat seeds decreased under different MPs, and the HDPE-MPs, medium particle size (1000 μm), and medium concentration (0.5 g·kg⁻¹) had the greatest inhibitory effect on wheat seed germination. The effects of MPs on wheat seed growth characteristics were inconsistent; the germination potential (GP), germination index (GI), and vitality index (VI) showed a significant decreasing trend under the PLA-MPs and medium-concentration (0.5 g·kg⁻¹) treatment, while the mean germination time (MGT) showed a significant increasing trend; the GP and MGT showed a significant decreasing and increasing trend under the high-particle-size (4000 μm) treatment, respectively, while the GI and VI showed a significant decreasing trend under the medium-particle-size (1000 μm) treatment. The growth characteristics of wheat plants showed a significant decreasing trend under different MPs, with the SPAD, nitrogen concentration of the leaves, and plant height decreasing the most under PLA-MP treatment, the SPAD and nitrogen concentration of leaves decreasing the most under low-particle-size (150 μm) and low-concentration (0.1 g·kg⁻¹) treatments, and the decreases in plant height under the high-particle-size (4000 μm) and high-concentration (1 g·kg⁻¹) treatments being the largest. There were significant increasing trends for ammonium nitrogen (NH₄⁺), total phosphorus (TP), soil urease (S-UE), soil acid phosphatase (S-ACP), and soil sucrase (S-SC) under different microplastics, while the PLA-MPs had a significant increasing trend for nitrate nitrogen (NO₃⁻) and a significant decreasing trend for pH; there was a significant decreasing trend for total nitrogen (TN) under the HDPE-MPs and PLA-MPs, and for each particle size and concentration, the PLA-MPs and low-concentration (0.1 g·kg⁻¹) treatments showed a significant decreasing trend for soil catalase (S-CAT). The research results could provide certain data and theoretical bases for evaluating the effects of MPs on crop growth and soil ecological environments. Full article