Search Results (279)

In response to growing global concerns about plastic waste, the development of efficient recycling technologies for thermoplastics has become increasingly important. Polypropylene (PP), a widely used commodity resin, is of particular interest because of the urgent need to establish sustainable material circulation. However, conventional mechanical property evaluations of injection-molded products typically require dedicated specimens, which involve additional material and energy costs. As described herein, we propose a simplified mechanical model to derive Poisson’s ratio and critical expansion stress directly from standard uniaxial tensile tests of molded thermoplastics. The method based on the true stress–true strain relationship in the small deformation region was validated using various thermoplastics (PP, POM, PC, and ABS), with results showing good agreement with those of the existing literature. The model was applied further to assess changes in mechanical properties of Homo-PP and Block-PP subjected to repeated extrusion. Both materials exhibited reductions in elastic modulus and critical expansion stress with increasing extrusion cycles, whereas Block-PP showed a slower degradation rate because of thermo-crosslinking in its ethylene–propylene rubber (EPR) phase. DSC and chemiluminescence analyses suggested changes in stereoregularity and radical formation as key factors. This method offers a practical approach for evaluating recycled PP and contributes to high-quality recycling and material design. Full article

Polycarboxylate superplasticizer (PCE) is an important part of improving the overall performance of concrete. However, its synthetic raw materials are overly dependent on petrochemical products, and it also causes problems such as environmental pollution. With the development of the building material industry, the demand for petrochemical resources required for synthetic water-reducing agents will increase rapidly. Therefore, there is an urgent need to transition the synthetic raw materials of PCE from petrochemicals to biomass materials to reduce the consumption of nonrenewable resources as well as the burden on the environment. Biomass materials are inexpensive, readily available and renewable. Utilizing biomass resources to develop good-performing water-reducing agents can reduce the consumption of fossil resources. This is conducive to carbon emission reduction in the concrete material industry. In addition, it promotes the high-value utilization of biomass resources. Therefore, in this study, a biomass polyether monomer, acryloyl hydroxyethyl cellulose (AHEC), was synthesized from cellulose via the reaction route of ethylene oxide (EO) etherification and acrylic acid (AA) esterification. Biomass polycarboxylate superplasticizers (PCE-Cs) were synthesized through free radical polymerization by substituting AHEC for a portion of the frequently utilized polyether monomer isopentenyl polyoxyethylene ether (TPEG). This study primarily focused on the properties of PCE-Cs in relation to cement. The findings of this study indicated that the synthesized PCE-C5 at a dosing of 0.4% (expressed as mass fraction of cement) when the AHEC substitution ratio was 5% achieved good water reduction properties and significant delays. With the same fluidity, PCE-C5 could enhance the mechanical strength of cement mortar by 30% to 40%. This study utilized green and low-carbon biomass resources to develop synthetic raw materials for water-reducing agents, which exhibited effective water-reducing performance and enhanced the utilization rate of biomass resources, demonstrating significant application value. Full article

The present study investigated the efficacy of edible coatings formulated with gellan gum and lemon peel extract (LPE) in preserving the postharvest quality of cherry tomatoes (Solanum lycopersicum var. cerasiforme). Selected fruits exhibiting uniform ripeness and free from defects were sanitized and coated with solutions containing different HAG/LAG (high- and low-acyl gellan gum) ratios, incorporating 4.0% (w/v) LPE. Physicochemical and physiological parameters, including soluble solids content, weight loss, pH, titratable acidity, oxygen consumption, carbon dioxide and ethylene production, skin redness (a*/b* ratio), and decay incidence, were systematically assessed under storage conditions of 25 °C and 70% relative humidity. HAG-coated fruits showed the lowest weight loss (1.08%), higher soluble solids (7.11 °Brix), and greater firmness (3.11 N/mm²) compared to uncoated controls. Moreover, they exhibited reduced oxygen consumption (0.06 mg·kg⁻¹·h⁻¹), ethylene production (3.10 mg·kg⁻¹·h⁻¹), and decay rate (2%). Redness was better preserved, and decay rates were substantially (p < 0.05) reduced throughout the storage period. These findings highlight the potential of HAG-based edible coatings enriched with LPE as an innovative postharvest technology to extend shelf life, maintain quality attributes, and reduce postharvest losses in cherry tomatoes. Full article

Today, the global production of plastic packaging reaches a million tons annually, resulting in significant amounts of plastic waste in the environment, which causes serious pollution issues and negatively affects the health of all living beings. However, the recycling rate for plastic packaging waste in Europe currently remains limited (~38%). With this in mind, this study focuses on the collection, characterization, and recycling, through pyrolysis, of 23 random plastic samples collected from food and non-food packaging waste in Greece. The samples were analyzed using thermal characterization techniques, such as Differential Scanning Calorimetry (DSC) and Evolved Gas Analysis (EGA), in conjunction with FTIR spectroscopy to gather important information and identify the polymers present in each sample. Furthermore, the samples underwent pyrolysis, resulting in valuable products such as the monomers styrene or ethylene, along with other useful secondary compounds, including benzoic acid, depending on the polymer type of each sample. The most prevalent polymer identified was PE (35%), while the remaining samples consisted of PET (22%), PP (22%), and PS (17%); only one sample was a blend of PE/PP. DSC facilitated the identification of the polyethylene type (LDPE, HDPE, or LLDPE). Full article

Flower senescence during transport is a major concern for exporters, as physiological disorders reduce quality and price. Extending vase life is crucial, and while 1-MCP is widely used, it requires low temperatures and is less effective in disease control. Cold plasma generated by dielectric barrier discharge produces reactive oxygen and nitrogen species (RONS), offering an alternative method for preserving cut flowers. This study compared the effectiveness of cold plasma and 1-MCP treatments on the vase life of Vanda ‘Pachara Blue’ orchids. Flowers were treated with T1 (control at 25 °C), T2 (1-MCP), and T3 (cold plasma). Both 1-MCP and cold plasma significantly reduced ethylene production (26.15 and 25.20 µL C₂H₄/kg/hr, respectively) and respiration rate (63.92 and 57.44 mg CO₂/kg/hr, respectively) compared to the control (40.93 µL C₂H₄/kg/hr and 118.21 mg CO₂/kg/hr). Vase life was extended to 19.33 days in both treatments, an 87.12% increase over the control (10.33 days). Additionally, cold plasma slightly improved water uptake and reduced petal discoloration. These findings indicate that cold plasma is a promising alternative to 1-MCP, offering effective flower preservation without the need for low-temperature conditions and potential additional benefits in floral quality. Full article

Government regulations have required consumer products—electrical and electronic components, toys, furniture, clothing, and cars— to meet ever-increasing flame resistance standards, and industry has met these norms by adding brominated fire retardants. However, end-of-life treatment and up-cycling of these plastics is challenging as the brominated compounds are endocrine disruptors, bioaccumulators, and persist in the environment. Pyrolysis, catalytic cracking, or combustion, to recover its fuel value, produces toxic brominated dibenzodioxins and dibenzofurans Here, we demonstrated the efficacy of a solvothermal treatment that extracts up to 99% of the bromine from high-impact polystyrene (HIPS) and polystyrene (PS) in electrical and electronic waste (e-waste). The process operated between 160 °C and 230 °C with ethylene glycol or triethylene glycol as the solvent and NaOH or KOH as the extraction agent (0.5 M to 2 M). The reaction rates depended on the particle size: 60 mm plastic chunks took up to between 4 and 24 h to react while fibers 3 mm in diameter reacted in less than 5 min. Full article

The packaging of perishable products, such as fruits, contributes to their preservation during storage and safe transportation. The use of suitable packaging materials contributes to forming a desirable atmosphere inside the package so that the level of respiration, transpiration, and ethylene emission can be kept low. However, it would be useful for consumers to know relevant information on the deterioration rate of different types of fruit (tree fruits, berries, stone fruits, and aggregate accessory fruits). The technology of intelligent and active packaging systems (smart packaging) enables the provision of information related to the deterioration rate of fruits to consumers and, in parallel, extends the shelf life of fruits and other plant-based foods, maintaining a high quality. Intelligent packaging systems include biosensors and gas sensors, along with microbial, freshness, and time–temperature indicators. On the other hand, the active packaging system includes the use of moisture, odor, and gas absorbers, along with antioxidant and antimicrobial agents to maintain the quality of plant-based foods and extend their shelf life. This review article aims to make an in-depth evaluation of the most relevant literature on this topic by highlighting the challenges, trends, and future directions related to different types of fruits. Full article

Apricots, known for their unique flavor and health advantages, experience external quality deterioration after harvest due to their climacteric characteristics, leading to a decrease in shelf life. This research examines the effects of 1-Methylcyclopropene (1-MCP) application on the post-harvest quality and volatile compound profiles of ‘Jizaohong’ apricots when stored under ambient conditions. After harvesting, apricots underwent treatment with 0.5, 1.0, and 1.5 µL L⁻¹ of 1-MCP for a duration of 24 h, subsequently being stored at ambient temperature (20 ± 1 °C). The results demonstrate that 1-MCP treatments reduced decay, respiration rates, and ethylene production, while also preserving fruit firmness and maintaining skin coloration. Furthermore, the application of 1-MCP markedly diminished the emission of volatile compounds in ‘Jizaohong’ apricots, while linear discriminant analysis (LDA) effectively distinguished between the treated fruits and the untreated controls. The correlation analysis revealed a relationship between the response values of the electronic nose and the quality of the fruit, supporting its potential for swift and non-invasive assessment. Among the concentrations evaluated, 1.0 µL L⁻¹ 1-MCP demonstrated the highest efficacy in minimizing decay and improving quality, whereas 1.5 µL L⁻¹ 1-MCP did not show notable variations in firmness or ethylene suppression. Thus, the application of 1.0 µL L⁻¹ 1-MCP after harvest serves as an effective method for preserving the quality of ‘Jizaohong’ apricots and prolonging their shelf life, while also enabling swift, non-invasive evaluations using the electronic nose. Full article

The selective chlorination of ethane to 1,2-dichloroethane offers a promising route for upgrading ethane, yet its efficiency remains constrained by limited mechanistic insights into gas-phase chlorine-radical-mediated pathways, which govern target product selectivity and competing dehydrochlorination side reactions. This work systematically decouples the kinetics of ethane chlorination and chloroethane functionalization under varying Cl₂ concentrations, revealing that chlorine radicals govern product distribution through thermodynamically favored pathways. This results in an interesting phenomenon whereby the product ratio between 1,1-C₂H₄Cl₂ and 1,2-C₂H₄Cl₂ maintains a constant 2:1 stoichiometry regardless of Cl₂ concentration variation. A critical observation is that the rate of all chlorination steps remains independent of alkane concentrations, highlighting the dominant role of chlorine radicals in rate-determining steps. Furthermore, ethylene byproducts are demonstrated to originate from the dechlorination of chlorine-radical-induced 2-chloroethyl radicals derived from chloroethane, rather than the direct dehydrochlorination of chloroethane itself. These insights into the dual role of chlorine radicals—mediating both the chlorination and dehydrochlorination pathways—establish a foundational framework for integrating gas-phase radical chemistry with catalytic engineering strategies to suppress undesired side reactions and enable scalable, selective ethane chlorination. Full article

Space charge injection in polypropylene (PP) significantly weakens the stability of HVDC cables. Impact polypropylene copolymer (IPC) is often used as insulation material for AC cables, but in the DC field, IPC has the problem of space charge accumulation. This is because there is a multi-phase structure inside the IPC to which ethylene monomer was added in the production process, and the difference in physicochemical properties of each phase is an important reason for the accumulation of space charge inside the material. In this work, the vinyl phases and propenyl phases of two types of IPC were separated. The film samples were prepared and tested at 30 °C and 50 °C for DC electrical conductivity, and at 30 °C, 50 °C, and 80 °C for space charge. The experimental results show that the DC conductivity of vinyl phases is significantly higher than that of propenyl phases in both types of IPC. The degrees of mismatch between the DC conductivity of vinyl phase and that of propenyl phase are different in the two types of IPC, and the mismatch degree of DC conductivity is from several times to hundreds of times. The conductivity of the two vinyl samples is ohmic. The conductivity of the two propenyl phases shows nonlinearity under different electric field intensity, and the mismatch degree of the two phases increases with temperature. Compared to untreated IPC, at all test temperatures, the maximum space charge density of the propenyl samples is much lower, which can be reduced by about 1/3 at 50 °C and by about 50% at 80 °C. The density of heteropolar charge produced by impurity ionization in the samples and the depth of electrode injection both decreased. At each temperature, the distortion rate of the electric field in propenyl samples is lower than that in IPC, the distortion rate can be reduced by more than 15%, and the distortion rate can be reduced by nearly half at 80 °C. The charge dissipation characteristic of propenyl samples during depolarization is also optimized compared with IPC samples, the time required for charge dissipation to reach stability is shortened, and the residual charge density in the sample is reduced at the end of depolarization. In addition, the relevance between the variation of DC conductivity of phases and space charge characteristics was discussed according to SCLC (space charge limited current) theory. This work provides a feasible reference for the manufacture of high-reliability polypropylene-based cable material with excellent insulation performance. Full article

The application of 1-methylcyclopropene (1-MCP) is widely used to extend the storage life of climacteric fruits, such as ‘Rocha’ pears. However, the suppression of ethylene’s action by 1-MCP often results in excessive ripening delay, compromising fruit quality and consumer acceptance. In this study, we investigated the potential of glyoxylic acid (GLA) to counteract the effects of 1-MCP and promote ripening. To evaluate this, ‘Rocha’ pears treated with 1-MCP were exposed to 3% (m/v) GLA and stored at 20 ± 2 °C for 15 days. Typical ripening indicators, such as firmness, skin color, ethylene production, respiration rate, volatile organic compounds (VOCs), sugars, and the activity of ethylene biosynthetic enzymes, were measured. Our results indicate that GLA did not induce significant effects on the ripening response, as ethylene production remained comparable to that of the control. Consequently, no significant changes in firmness, skin yellowing, or sugar content were observed in the GLA-treated pears. However, GLA significantly increased respiration rates (approximately 57%) and induced higher emissions of stress-associated VOCs, including hexanal, (E)-2-hexenal, and ethanol. This suggests that GLA may influence metabolic pathways related to energy metabolism and redox homeostasis without necessarily triggering ethylene-induced ripening. This study provides new insights into the interactions between GLA, 1-MCP, and fruit development, contributing to the development of alternative strategies to manage the effects of 1-MCP in ‘Rocha’ pear storage. Full article

Aluminum hydroxide (ATH) is an environmentally friendly flame retardant widely employed in polymers. However, the high loading of ATH, due to its limited efficiency, potentially compromises other properties, including mechanical properties. This work explores a feasible ball milling strategy for high-efficiency ATH-based flame retardants (PPA-ATH and PPOA-ATH), fabricated by employing phenylphosphinic acid (PPA) and phenylphosphonic acid (PPOA) as surface modifiers and water as the processing solvent. The characterization study of PPA-ATH and PPOA-ATH demonstrates that ball milling effectively reduces their particle size, enhances their specific surface area, and improves their dispersibility within the ethylene-vinyl acetate (EVA) matrix. PPOA-ATH exhibited superior capabilities in enhancing the thermal stability and flame retardancy of EVA composites compared to PPA-ATH. The incorporation of PPOA-ATH resulted in the retarding in the temperature at 50% mass loss by 21 °C and an increase in the char residue of 34.5% at 700 °C. Furthermore, PPOA incorporation led to reductions of 81.0% in the peak heat release rate, 48.1% in the total heat release, 73.7% in the peak smoke production rate, and 41.2% in the total smoke production compared to neat EVA. This green modification strategy successfully addresses the application limitations of ATH, providing a feasible and environmentally friendly method for high-efficiency ATH-based flame retardant fabrication. Full article

Mango fruits are susceptible to cold stress under prolonged storage. Melatonin (MT) is a phytohormone well known for enhancing the tolerance and overall quality of various tropical and subtropical fruits during cold storage. This study investigated the effects of MT treatment on the postharvest quality of mango fruits during prolonged cold storage. Mangoes were treated with different concentrations of MT (1.0 mM (T1), 1.5 mM (T2), 2.0 mM (T3), and 2.5 mM (T4)) and stored for 45 days under cold conditions (15 °C and 90% relative humidity). Control fruits had no MT treatments. Various physicochemical, phytochemical, antioxidant, and enzymatic activities were monitored every 5 days throughout the storage period. MT treatment significantly reduced the weight loss and decay rates compared to control samples, with T3 and T4 treatments showing superior effectiveness. Due to severe decay in the control samples, the storage period was terminated on day 25, whereas the MT treatment protected the mango fruits and allowed for the completion of all 45 days of storage. The MT treatments effectively maintained color characteristics, reduced respiration rates, and suppressed ethylene production in mango fruits compared to the control samples. Higher MT concentrations preserved firmness and controlled malondialdehyde accumulation (p < 0.05). Chemical properties, including the starch content, total soluble solids, and titratable acidity, were better maintained in MT-treated fruits. The treatments also enhanced the retention of phytochemicals (ascorbic acid, total phenolic, and total flavonoid contents) and improved antioxidant activities against DPPH and ABTS radicals. Furthermore, MT treatment effectively regulated the activities of browning-related enzymes (polyphenol oxidase (PPO) and peroxidase (POD)), cell wall-degrading enzymes (polygalacturonase (PG), pectin methylesterase (PME), and lipoxygenase (LOX)), and antioxidant enzymes (superoxide dismutase (SOD) and ascorbate peroxidase (APX)). The results demonstrate that MT treatment, particularly at higher concentrations (T3 and T4), effectively extends the storage life and maintains the quality of mango fruits during prolonged cold storage. Full article

Packaging materials mainly serve the function of protecting products. The most common representative of this group is poly(ethylene terephthalate) (PET), which is not biodegradable and therefore, its waste might be burdensome to the environment. Thus, this work aims to develop outlines for obtaining polyester-based systems, preferably biobased ones, intended for the packaging industry and their detailed characterization. The obtained multilayer systems based on two biobased thermoplastic polyesters, i.e., poly(ethylene 2,5-furandicarboxylate) (PEF) and the “double green” polylactide (PLA), were subjected to various analyses, i.e., UV-Vis spectrophotometry, microscopic evaluation, tensile tests, differential scanning calorimetry (DSC), oxygen transmission rate (OTR), water absorption tests, surface analyses, and biofilm formation. The best possible arrangement was selected in terms of the packaging industry. It was proven that the elastic modulus was significantly higher for multilayer systems, whilst higher-strength parameters were observed for PLA single foils. Regardless of thickness, PLA and PEF foils exhibit similar absorption values in cold water. Moreover, PEF foils demonstrated significantly better barrier properties towards oxygen gas compared to PLA foils of the same thickness. However, a multilayer system composed of two PLA foils with a single inner PEF foil had an OTR value only slightly higher than that of the PEF foil alone. PEF was also found to be a material that exhibited a limited formation of bacterial biofilm, particularly strains of S. aureus and E. coli. All of the above findings clearly confirm the sensibility of the research topic undertaken in this work on the application of biobased thermoplastic polyesters in the packaging industry. Full article

Ethylene glycol (EG) is a contaminant in the wastewater of airports because it is commonly used in aircraft deicing fluids during the cold season in northern regions. Ethylene glycol by itself has relatively low toxicity to mammals and aquatic organisms, but it can lead to a substantial increase in chemical and biological oxygen demands. The contamination of water with EG facilitates the rapid growth of microbial biofilms, which decreases the concentration of dissolved oxygen in water and negatively affects overall biodiversity. The development of a simple method to decompose EG with high efficiency and low operating costs is important. This study revealed that ethylene glycol can be completely oxidized using UV-C activated hydrogen peroxide (H₂O₂/UV-C) at a high rate (up to 56 mg L⁻¹ h⁻¹) at an optimum EG:H₂O₂ molar ratio of 1:10–1:15. Air purging the reaction mixture at 1000 cm³ min⁻¹ increases the EG mineralization rate up to two times because the simultaneous action of UV-activated H₂O₂ and O₂ (H₂O₂ + O₂/UV-C) leads to a synergistic effect, especially at low EG:H₂O₂ ratios. The kinetics and mechanism of EG degradation are discussed on the basis of the concentration profiles of ethylene glycol and intermediate products. Full article