Search Results (252)

Many researchers are interested in the behavior of voided concrete members, which are used to increase flexural capacity by increasing the section depth. However, few studies have concerned ways to expand the voids to increase the self-weight loss while maintaining the permitted carrying capacity of these members. This study deals with the effect of a void scheme to further reduce the weight of glass fiber-reinforced polymer (GFRP) one-way reinforced concrete (RC) slabs by benefiting from the anti-classical curvature of one-way RC slabs. This study also incorporates green structures by using non-degradable plastic bottles in the RC one-way slabs. Three void configurations are used in this study: straight-line, back-to-back, and front-to-front void schemes. Specimens with the straight-line void configuration achieve the highest ultimate load capacity, reaching 91% of the solid reference slab’s capacity if reinforced near the minimum reinforcement ratio and 101% if used with a 30% larger GFRP reinforcement ratio. The back-to-back curved configuration is identified as the most efficient design, providing a 10.3% reduction in self-weight while retaining 83% of the solid slab’s ultimate load capacity, as compared with the front-to-front configuration, which retains only 73%. Full article

Polyethylene terephthalate (PET) is a synthetic polymer that is widely used in the production of textiles, packaging materials, and beverage bottles. However, its high durability and resistance to abiotic degradation result in serious environmental and health problems. PETase is an enzyme that can depolymerize PET into value-added products, thereby providing an environmentally friendly strategy for PET recycling. PETaseSM14 from a marine sponge, Streptomyces sp. SM14, has a high salt tolerance and thermal stability, thus suggesting its potential for PET degradation applications. However, the substrate recognition mechanism of PETase remains unclear because the catalytic residue is buried within residues that form the substrate-binding cleft. To elucidate the molecular mechanism of PETaseSM14, all-atom molecular dynamics simulations were performed at 300, 320, and 340 K. The results revealed that the overall α/β fold remained stable at all temperatures, whereas temperature-dependent local fluctuations and conformational changes were observed in the substrate-binding cleft and N-terminal region. At 300 and 320 K, positional shifts and conformational changes in Tyr88 exposed the catalytic Ser156 to the solvent, thereby forming a potential substrate-binding cleft. In contrast, at 340 K, which is higher than the melting temperature of PETaseSM14, disruption of the charge-relay system of the catalytic triad occurs through conformational changes in His234. Substantial temperature-dependent conformational and positional changes in the N-terminal region of PETaseSM14 were observed at 320 and 340 K. These results provide mechanistic insight into the temperature-dependent active-site rearrangements and offer rational engineering strategies to enhance the efficiency of PETase for PET biodegradation. Full article

While various disturbances in organisms have been reported following long-term oral exposure to small plastic particles (microplastic particles, MPs), the effects of acute, short-term encounters remain underrepresented in scientific research. In this study, adult male Wistar rats were orally gavaged with MPs of three different sizes (~41 µm, 70 µm, or 106 µm; dose: 35 mg/kg), originating from poly(ethylene terephthalate) (PET) bottles. Twenty-four hours post-exposure, the impact on overall health indicators, including food and water intake, sensorimotor function and clinical signs of toxicity, in addition to serum biochemical markers related to organ function and oxidative stress, were assessed. Although no overt sensorimotor impairments or visible toxicity signs were observed in all MPs-treated groups, several investigated biochemical parameters were significantly altered. Water intake was also modified, whereas reduced food intake occurred only in the group treated with median-sized MPs, suggesting that acute exposure to MPs can lead to early physiological and biochemical responses. The obtained results, compared to the data extracted by using machine-learning (ML) tools and GPT-5 model within the available literature, highlighted the importance of investigating the acute effects of MPs, which may precede or contribute to long-term health consequences. Full article

Reducing dependence on fossil-based feedstocks for packaging can be achieved through three complementary strategies: minimizing packaging use, increasing closed-loop recycling rates, and expanding the adoption of renewable (e.g., biobased) packaging materials. To ensure these defossilization pathways reinforce rather than hinder one another, it is essential to understand how new biobased materials interact with existing recycling streams. With the market introduction of packaging containing the biobased polyester poly(ethylene 2,5-furandicarboxylate) (PEF) approaching, several studies have investigated blends and copolyesters of poly(ethylene terephthalate) (PET) and PEF. This study expands current knowledge of thermomechanical and crystallization behavior by examining the influence of PEF on the mechanical recycling process of bottle-grade PET. Processing behavior was assessed at various PEF contents at both laboratory and industrial scales, and the resulting recycled resin and bottles were analyzed for color, crystallization behavior, and bottle performance. Although the melting temperature decreased with rising PEF content, no negative impact on the industrial recycling process investigated was observed for PEF levels up to 10 wt%. Two notable trends emerged: increasing PEF content reduced crystallization rate, yielding bottles with higher transparency, while yellowness also increased. Ongoing research aims to understand and mitigate this rise in yellowness. Full article

Micro- and nanoplastics (MNPs) are increasingly contaminating atmospheric particulates, yet their influence on PM_2.5 chemistry and toxicity remains poorly understood. This study investigates how secondary MNPs derived from common products (water bottles, coffee cups, and food plates) alter the properties of PM_2.5. We evaluated PM_2.5 leaching characteristics, oxidative potential, inflammatory activity, and bacterial-based cytological and metabolomic responses after 24 h of exposure to three MNP doses. MNPs markedly altered PM_2.5 chromophoric composition, with bottle-derived (PET) MNPs inducing the strongest increases in aromaticity, humification, and slope factor, followed by coffee cups (PLA/paper) and food plates (PP). These leaching shifts aligned with polymer-specific redox behaviors: bottle-derived MNPs enhanced antioxidant enrichment at high PM_2.5, whereas cup-derived MNPs produced the most pronounced protein-denaturation-based inflammatory activity. Escherichia coli assays showed non-linear growth responses, elevated reactive oxygen species, altered carbohydrate secretion, and membrane and protein perturbations that paralleled PM_2.5 chemical reactivity. FTIR metabolomic fingerprints revealed dose- and polymer-dependent disruptions in polysaccharide, lipid, and protein domains. Overall, the results demonstrate a mechanistic cascade in which MNP exposure reshapes PM_2.5 chemistry, amplifies oxidative and inflammatory potential, and culminates in measurable cytological and metabolic stress, with polymer identity (PET > PLA/paper > PP) as the dominant driver. Full article

In recent years, sustainability and the concept of a circular economy have grown in importance within almost all industrial sectors. Especially in the chemical industry, recycling of polymer waste streams has become an important pathway to avoid plastic waste being landfilled or incinerated. Additionally, traditional carbon sources, such as fossil fuels, can be substituted with streams of recycled polymer. For example, polyethylene terephthalate (PET), which is utilized in plastic bottles and textiles, may be recycled via glycolysis. This depolymerization yields the monomer bis(2-hydroxyethyl) terephthalate (BHET). This study focuses on the thermal behavior and stability of BHET, both in pure form as well as in the presence of ethylene glycol (EG), as it results from PET glycolysis. For this, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC), powder X-ray diffraction (PXRD), and thermogravimetry (TG) were utilized. The results exhibited pure BHET polymerizing to PET at temperatures above 120 °C, while further increasing temperatures increased the reaction kinetics. Additionally, no reaction was observed in BHET/EG mixtures at any temperature investigated, which can be attributed to the presence of EG shifting the equilibrium of the reaction towards the BHET, thus inhibiting polymerization. Based on these results and the determined BHET/EG (solubility) phase diagram, potential purification strategies based on crystallization are proposed. Full article

Background: Growing interest in sustainable packaging materials, such as recycled polyethylene terephthalate (rPET), raises the question of whether they can effectively replace traditional glass in packaging cold-pressed vegetable oils, which are particularly susceptible to oxidation. Methods: Rapeseed oil and golden flaxseed oil were analyzed after 6 months of storage in glass and rPET bottles at 4 °C and 21 °C. Peroxide value, tocopherol content, sterol and oxyphytosterol profiles, color parameters, and triacylglycerol composition were evaluated using validated ISO/AOCS, HPLC, and GC methods; results were subjected to ANOVA statistical analysis. Results: Temperature was shown to be the main factor determining the rate of degradation, and flaxseed oil exhibited significantly lower oxidative stability compared with rapeseed oil. At 21 °C, a rapid increase in peroxide value, intensive tocopherol degradation, greater sterol losses, and deterioration of color were observed, particularly in samples stored in rPET. At 4 °C, the rate of change was markedly lower, and differences between glass and rPET remained minimal. Conclusions: Glass provides the best protection against oxidation; however, rPET can serve as a suitable packaging material for vegetable oils with higher oxidative stability stored under refrigerated conditions; at room temperature, it promotes a noticeable deterioration in oil quality. Full article

Mechanical recycling of polyethylene terephthalate (PET) is a key strategy for circular packaging applications; however, repeated thermo-mechanical processing leads to progressive polymer degradation. In this study, the effect of controlled repeated extrusion on the degradation behavior of bottle-grade PET was systematically investigated under laboratory conditions. Mechanical recycling was simulated using a co-rotating twin-screw extruder, where PET was subjected to up to four consecutive processing cycles corresponding to a cumulative residence time of 8 min. Progressive processing resulted in chain scission, reflected by a decrease in intrinsic viscosity from approximately 0.80 to 0.65 dL·g⁻¹ and a corresponding reduction in molecular weight. Melt flow rate increased accordingly, indicating a gradual loss of melt strength. Differential scanning calorimetry revealed that the glass transition and melting temperatures remained nearly unchanged, while the degree of crystallinity increased from approximately 23.0% to 29.5%, accompanied by changes in crystallization behavior. These structural changes led to reduced ductility, with elongation at break decreasing from about 84% to 60%. Optical analysis showed systematic material darkening, and a strong linear correlation between lightness (L*) and intrinsic viscosity was observed. By isolating intrinsic thermo-mechanical degradation effects under controlled processing conditions, this study enables a clearer definition of realistic reuse limits for mechanically recycled bottle-grade PET. The results indicate that bottle-grade PET retains properties compatible with demanding applications only after a limited number of thermo-mechanical processing cycles, whereas further processing restricts its usability to less demanding applications such as fibers, films, and non-food packaging. Full article

The chemical recycling process of polyethylene terephthalate (PET) was executed through aminolysis employing N, N-Diisopropylethylamine (DIPEA) as the catalytic agent, commencing with the systematic collection and comprehensive purification of discarded PET bottles to remove contaminants and additives. The depolymerization reaction utilized hydrazine as the primary amine source, facilitating the cleavage of ester bonds within the polymer matrix under controlled temperature and pressure conditions. The synthesis of the diamine compound, terephthalohydrazide, was successfully achieved through this catalytic aminolysis pathway, demonstrating high conversion efficiency and product selectivity. The resulting terephthalohydrazide served as a crucial intermediate and was subsequently utilized for the further synthesis of bis-1,3,4-Oxadiazole derivatives through a comprehensive methodology rigorously aligned with the fundamental principles of green chemistry, including atom economy, reduced waste generation, and environmentally benign reaction conditions. A diverse series of six distinct products derived from various carboxylic acids employed in the cyclization synthesis of bis-1,3,4-Oxadiazoles were systematically produced under optimized reaction parameters. These products were meticulously characterized using advanced nuclear magnetic resonance (NMR) spectroscopy techniques, including both ¹H and ¹³C NMR analyses, confirming their structural integrity and chemical composition. This sequential approach represents a significant advancement in heterocyclic synthesis methodology, using sustainable pathways to find structural diversity. Full article

Plastic is a key industrial innovation with wide ranging applications. However, its extensive production, consumption, and inadequate disposal practices have created a complex environmental challenge, resulting in escalating ecological and public health impacts. This study examines plastic waste management practices in the rural coastal communities of Kendwa, Nungwi, Paje, and Michamvi, located near tourist hotels in Zanzibar’s Northern and Southern districts, Tanzania. Structured interviews, observation checklists, and participatory workshops were used to assess the types of plastic waste generated and the level of community engagement in disposal practices. Findings indicate that single-use polyethylene terephthalate (PET) and high-density polyethylene (HDPE) packaging, particularly beverage bottles and other disposable items from hotels, dominate the waste stream. Nungwi and Kendwa demonstrate proactive responses, supported by a professional waste management company and NGO-led awareness programs promoting sustainable practices. In contrast, Paje and Michamvi continue to face challenges from tourism-linked waste, highlighting disparities in local management capacity. Despite positive initiatives in Nungwi and Kendwa, persistent littering remains a problem due to weak enforcement, limited infrastructure, and inconsistent community compliance. To address these gaps, the study recommends implementing waste bank programs alongside financial sustainability measures and community empowerment initiatives, to reinforce existing efforts and advance more sustainable waste management. Full article

HDPE caps are collected together with PET bottles, which have been recycled into new bottles for decades. Due to Deposit Return Schemes, the bottle caps are sorted by type and are suitable to be recycled again for sensitive applications e.g., food contact. While there are evaluation criteria for mechanical PET recycling processes, no such evaluation crite-ria have been published for recycled HDPE caps in food contact. As part of the study, possible evaluation criteria are derived from other polymers or applications and critically discussed. Recycling of post-consumer caps from beverage bottles into new HDPE caps in direct contact with food is realistic even if worst-case considerations on the evaluation criteria are applied. The required cleaning efficiencies are within a range that is technically feasible for today’s mechanical HDPE recycling processes. The evaluation criteria can be used for a preliminary assessment of post-consumer HDPE recyclate in food contact. Based on the evaluation, the recycling of HDPE caps is to be submitted as a novel technology according to Regulation 2022/1616. Full article

The increasing environmental concerns surrounding plastic waste have intensified recycling efforts, particularly in the textile industry, where poly(ethylene terephthalate) (PET) is widely used for sustainable material production. The growing use of recycled PET (rPET) in textiles has prompted the need for reliable analytical methods to detect and quantify rPET content. This study differentiates between virgin and recycled PET by simulating mechanical recycling through five reprocessing cycles of three distinct PET grades, assessing changes in crystalline structure, intrinsic viscosity, molecular weight, and specific degradation markers. Differential Scanning Calorimetry revealed bimodal melting behaviour in reprocessed samples, while intrinsic viscosity and Gel Permeation Chromatography indicated molecular degradation. Notably, the release of dimethyl terephthalate (DMT) and dimethyl isophthalate (DMiP) was consistently observed as a function of degradation. These markers were identified and quantified using High-Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC), with GC offering higher sensitivity and lower matrix interference. This study demonstrates that DMT and DMiP are robust chemical indicators of PET degradation and recycled content. This analytical approach, combining thermal, rheological, and chromatographic techniques, provides a scientifically sound and potentially cost-effective basis for traceability systems, certification protocols, and regulatory compliance in sustainable textile production. Full article

This study explores the potential use of Polyethylene Terephthalate (PET) plastic bottles as void makers in short reinforced concrete columns under pure axial compression. Such a scheme promotes sustainability by decreasing the consumption of concrete and reducing the pollution that comes with the disposal of PET bottles. The experimental component of this study consisted of testing 16 reinforced concrete columns divided into two groups, based on the cross-section dimensions. One group contained eight columns of a length of 900 mm with a net cross-sectional area of about 40,000 mm², while the second group contained eight columns of a length of 1100 mm with a net cross-sectional area of about 62,500 mm². The diameter of the void within the small cross-section group was 100 mm and within the large cross-section group was 265 mm. The experimental program includes pairs of solid and corresponding void specimens with consideration of the size of the longitudinal steel reinforcement, lateral tie spacing, and concrete compressive strength. The tests are conducted using a universal test machine under displacement-controlled loading conditions with the help of strain gauges and Linear Variable differential transformers (LVDTs). The analysis of the test results showed that the columns that were embedded with a small void that occupied about 30% of the core area exhibited reductions of 9% in the ultimate capacity, 14% in initial stiffness, 20% in ductility, and 1% in residual strength. On the other hand, the columns that contained a large void occupying about 60% of the core area demonstrated reductions of 24% in the ultimate capacity, 34% in initial stiffness, and 26% in ductility, although the residual strength was slightly increased by 5%. The reason for the deficiency in the structural response in the latter case is because the void occupied a significant fraction of the concrete core. The theoretical part of this study showed that the ACI 318 code provisions can reasonably predict the uniaxial compressive strength of columns embedded with PET bottles if the void does not occupy more than 30% of the concrete core. This study confirmed that short columns embedded with relatively small voids made from PET bottles and subjected to pure axial compression create a balance between sustainability benefits and a structural performance tradeoff. Full article

The growing use of plastics in food packaging has raised concerns about chemical migration into consumables, posing potential health risks. Ensuring the safety of packaging materials is a critical public health priority. This study aimed to validate an analytical method for qualitative and quantitative determination of BPs in bottled water and evaluate their presence in PET and rPET matrices. The method was validated through recovery tests for eight BPs (Bisphenol A, Bisphenol S, Bisphenol F, Bisphenol AF, Bisphenol AP, Bisphenol B, Bisphenol Z, and Bisphenol P). Linearity (R² ≥ 0.990) and high recovery rates proved the method’s stability, reliability, and accuracy. For bottled water, LODs ranged 0.030–0.075 µg/L and LOQs 0.10–0.25 µg/L; for PET/rPET, LODs were 0.00030–0.00075 mg/kg and LOQs 0.0010–0.0025 mg/kg. Mean recoveries in bottled water were in the range 89–109%, in PET from 94% to 117%, and in rPET from 106% to 118%. The results showed that BPA was quantifiable in all matrices, while other BPs remained below the limit of quantification. The validated method provides a robust tool for assessing bisphenol contamination and supports ongoing efforts to enhance food safety and inform regulatory frameworks for sustainable PET recycling. Full article