Recycled Polyethylene Terephthalate Research Articles

Endothermic–Exothermic Hybrid Foaming of Recycled PET Blends

Over the past decades, the use of polyethylene terephthalate (PET) has seen significant growth, particularly in the packaging industry. However, its long decomposition time poses serious environmental challenges. The aim of this research was to develop a process for the foaming of large quantities of recycled PET (rPET) using endothermic and exothermic foaming agents. Various formulations with different ratios of endothermic and exothermic foaming agents were prepared, as well as their mixtures. The study found that the endothermic–exothermic hybrid foaming process resulted in a finer cell-size distribution and enhanced mechanical properties, making the foams highly suitable for widespread applications. The results support the potential use of exothermic foaming agents as nucleating agents in a hybrid foaming system. In particular, the ratio of 3% endothermic and 1% exothermic foaming agents proved optimal in terms of achieving a balance between porosity and mechanical strength, thereby enabling broad industrial applicability.

The Investigation of Morphological and Mechanical Properties of Polymer-Based Electrospun Nanofiber Coated Polystyrene and Recycled Polyethylene Terephthalate Composite Materials

The Investigation of Morphological and Mechanical Properties of Polymer-Based Electrospun Nanofiber Coated Polystyrene and Recycled Polyethylene Terephthalate Composite Materials

Circular economy solutions for plastic waste: improving rheological properties of recycled polyethylene terephthalate (r-PET) for direct 3D printing

Circular economy solutions for plastic waste: improving rheological properties of recycled polyethylene terephthalate (r-PET) for direct 3D printing

Chemical recycling of polyethylene terephthalate using a micro-sized MgO-incorporated SiO2 catalyst to produce highly pure bis(2-hydroxyethyl) terephthalate in high yield

Chemical recycling is a feasible method for achieving the closed-loop recycling of polyethylene terephthalate (PET). In this strategy, post-consumer PET is depolymerized to bis(2-hydroxyethyl) terephthalate (BHET) via glycolysis, which is then repolymerized to yield recycled PET (rPET). Herein, we introduce an innovative approach for the chemical recycling of PET that focuses on glycolysis facilitated by a microsized MgO-incorporated SiO2 catalyst. This choice of catalyst is groundbreaking owing its superior glycolysis-catalysis efficiency and the ease with which it can be separated from the reaction mixture, thereby addressing the common challenges faced by traditional catalysts during PET depolymerization. By employing a heterogeneous catalyst with significantly larger particles than a conventional catalyst, we not only aimed to simplify the catalyst-removal process, thereby improving BHET purity, but also observed enhanced efficiency during the catalytic reaction that led to a superior yield of the desired product. The catalyst was synthesized using a wet impregnation method and its efficiency was evaluated at various reaction times and dosages, which revealed that the microsized MgO/SiO2 catalyst significantly outperforms traditional catalysts, to deliver a 95.1% yield of BHET with negligible amounts of metal detected in the final product. This study not only demonstrated the potential of microsized catalysts during PET glycolysis, but also contributes to the advancement of sustainable PET-recycling practices. We anticipate that the microsized MgO/SiO2 catalyst is a promising alternative for the industrial upcycling of PET waste.

A Systems Firm-Centered Perspective on the Environmental Assessment of Recyclable PET and Glass Soft Drink Containers

This paper adopts a systems firm-centered perspective on the environmental assessment of recyclable glass and PET soft drink containers. We employ LCA and discrete-event simulation modeling for the environmental assessment of the two soft drinks packaging alternatives in operational terms over the entire supply chain over a period of three years. The assessment is based on real data collected from a large soft drink producer and its suppliers. The research and practice contribution of the paper is twofold: first, it introduces a methodological framework for environmental assessment of companies’ packaging environmental impact under different product and operations strategies; and secondly, it provides a holistic environmental assessment of the two packaging materials (PET and glass) taking into account specific operational issues, such as product mix and recycling and reuse options, as well as activity interdependences and stochasticity. The results of the simulation experiments confirm at the operations system level, for glass, the importance for sustainability, to increase the number of reuse cycles (for the particular case, for significant improvement, seven reuses) and the percentage of used bottles collected for refilling (80% recovery rate), whereas for PET, to increase the percentage of recycled PET in new bottles (towards 30%).

Unraveling the Interplay between Stability and Flexibility in the Design of Polyethylene Terephthalate (PET) Hydrolases.

The accumulation of polyethylene terephthalate (PET), a widely used polyester plastic in packaging and textiles, has led to a global environmental crisis. Biodegradation presents a promising strategy for PET recycling, with PET hydrolases (PETase) undertaking the task at the molecular level. Unfortunately, PETase operates only at ambient temperatures with low efficiency, limiting its industrial application. Current engineering efforts focus on enhancing the thermostability of PETase, but increased stability can reduce the structural dynamics needed for substrate binding, potentially slowing enzymatic activity. To elucidate the balance between stability and flexibility in optimizing PETase catalytic activity, we performed theoretical investigations on both wild-type PETase (WT-PETase) and a thermophilic variant (Thermo-PETase) using molecular dynamics simulations and frustration analysis. Despite being initially designed to stabilize the native structure of the enzyme, our findings reveal that Thermo-PETase exhibits an unprecedented increase in structural flexibility at the PET-binding and catalytic sites, beneficial for substrate recruitment and product release, compared to WT-PETase. Upon PET binding, we observed that the structural dynamics of Thermo-PETase is largely quenched, favoring the proximity between the catalytic residues and the carbonyl of the PET substrate. This may potentially contribute to a higher probability of a catalytic reaction occurring in Thermo-PETase compared to WT-PETase. We suggest that Thermo-PETase can exhibit higher PET-degradation performance than WT-PETase across a broad temperature range by leveraging stability and flexibility at high and low temperatures, respectively. Our findings provide valuable insights into how PETase optimizes its enzymatic performance by balancing stability and flexibility, which may contribute to future PETase design strategies.

Tailoring properties of PET-derived Sn-MOFs through efficiency structure defects using trifluoroacetic acid (TFA) with water-based facile and green synthesis route

BackgroundThe synthesis of Metal-Organic Frameworks (MOFs) is increasingly focused on achieving green and cost-efficient methods while producing high-quality products with abundant active sites. This approach is attracting significant attention from researchers. One promising method, modulated synthesis, stands out for its ability to induce structural defects in MOFs and enhance their active sites. However, the challenges in identifying the optimal conditions for critical factors, particularly the quantitative correlation between the modulator and crucial independent variables influencing MOFs performance, underscore the importance of research work in this field. MethodsThis study synthesized tin-based MOFs (Sn-MOFs) utilizing a linker derived from recycled polyethylene terephthalate (PET) waste. A hydrothermal approach was employed, utilizing water-like solvents and trifluoroacetic acid (TFA) as a modulator to effectively induce structural defects. Response Surface Methodology (RSM) was applied to evaluate the effects and interactions of temperature, reaction time, and TFA concentration on optimizing yield and crystalline index (CI) while simultaneously reducing the residual percentage of 1,4-benzene dicarboxylate (H2BDC) in the Sn-MOFs (DI). Significant findingsThe research revealed that temperature, reaction time, and TFA concentration significantly influenced the performance of Sn-MOFs, highlighting the considerable potential of TFA in creating active sites and enhancing the surface area and pore volume of Sn-MOFs through defect engineering. Optimal synthesis conditions for Sn-MOFs included a temperature of 148℃, a reaction time of 24 h, and a molar ratio of H2BDC/TFA of 1.7, yielding 98.51 ± 1.47 % for yield and 80.21 ± 1.32 % for CI, with no detectable residual H2BDC. The resulting Sn-MOF-150 exhibited characteristics such as high thermal and chemical stability, abundant function groups, and a unique hierarchical nanostructure composed of spherical nanoparticles. These findings further emphasize the efficacy of the synthesis approach for Sn-MOF through critical parameter optimization and defect engineering techniques.

Epoxy asphalt binder reinforced with waste polyethylene terephthalate (PET) for improving toughness

ABSTRACT The instinct brittleness of epoxy resin is one of the challenges to the durability of epoxy asphalt pavements, which may cause various failures, such as cracking, potholes and delamination. To improve the toughness of epoxy asphalts, polymer tougheners have been commonly introduced. On the other hand, the rapid accumulation of unrecycled end-of-life polyethylene terephthalate (PET) waste brings a serious environmental problem. Addressing this, the research aims to explore the use of recycled PET (rPET) as a value-added toughener for epoxy asphalt binders. To obtain this goal, waste PET bottles were cut into flakes and integrated into asphalt binders to prepare rPET modified epoxy asphalt binders. The effect of the rPET content on the phase-separated morphology, rotational viscosity and mechanical and thermal properties of epoxy asphalt binder was studied. Notably, rPET dissolved in the asphalt binder, preventing the occurrence of phase separation in the discontinuous phase of rPET modified epoxy asphalt binders. The addition of rPET increased the viscosity, dynamic modulus and the glass transition temperature (Tg) of epoxy of epoxy asphalt binder. Furthermore, the mechanical properties and low-temperature performance of epoxy asphalt binder were also augmented. Remarkably, with the addition of 3 wt% rPET, the toughness of epoxy asphalt binder increased by 48%.

Plasma-Constructed Co2P-Ni2P Heterointerface for Electro‑Upcycling of Polyethylene Terephthalate Plastic to Co-Produce Hydrogen and Formate.

Integrating electrochemical upcycling of polyethylene-terephthalate (PET) and the hydrogen evolution reaction (HER) is an energy-saving approach for electrolytic hydrogen (H2) production, along with the coproduction of formate. Herein, a novel and rapid strategy of cold plasma phosphating is employed to synthesize Co2P-Ni2P heterointerface decorated on carbon cloth (Co2P-Ni2P/CC) to catalyze H2 generation and reform PET. Notably, the obtained Co2P-Ni2P/CC exhibits eminent ethylene glycol oxidation reaction (EGOR) and HER activities, effectuating low potentials of merely 1.300 and -0.112V versus RHE at 100mAcm-2 for the EGOR and HER, respectively, also attaining an ultralow cell bias of 1.300V at 10mAcm-2 for EG oxidation assisted-water splitting. DFT and characterization results validate that the as-formed built-in electric fields in the Co2P-Ni2P heterointerface can accelerate electrons transfer and deepen structural self-reconstruction, thereby boosting effectively water dissociation and ethylene glycol (EG) dehydrogenation. Impressively, coupling HER with PET-derived EG-to-formate in a flow-cell electrolyzer assembled with Co2P-Ni2P/CC pair achieves an intriguing formate Faradaic efficiency of 90.6% and an extraordinary stable operation of over 70h at 100mAcm-2. The work exemplifies a facile and effective strategy for synthesizing metal phosphides electrocatalysts with extraordinary performance toward H2 generation of water splitting and recycling of PET.

An experimental and numerical effort on the vibration behavior of additively manufactured recycled polyethylene terephthalate glycol components

AbstractThe importance of recycling engineering components and thus obtaining low‐cost production solutions has become prominent in today's world. In this study, the mechanical and dynamic behaviors of three‐dimensional‐printed recycled polyethylene terephthalate glycol (RePET‐G) beams were investigated numerically and experimentally for the first time in the literature. Initially, the governing equations of the beams were determined according to the Bernoulli–Euler beam theory, and these equations were numerically solved using the differential quadrature method and ANSYS program. Subsequently, to validate the accuracy of the numerical models, the obtained natural frequencies were compared with experimental results. It was observed that the numerical results showed good agreement with the experimental results. Finally, the effects of beam length, infill rate, and building direction on the natural frequencies of RePET‐G beams were investigated. The outcomes showed that as the beam length changed, natural frequencies were significantly affected. Increasing the infill rate, especially for beams with vertical building direction, from 20% to 100% led to a slight decrease in the natural frequency values of the structure. Moreover, it was found that for beams with an infill rate of 100%, the natural frequency values obtained in the horizontal building direction were higher than those obtained in the vertical building direction.Highlights Printable recycled filaments have great potential for vibration applications. Sample length affects the first natural frequency value of RePETG parts. Differential quadrature and ANSYS methods can be utilized for the vibration. For the 3D‐printed samples, rising infill rate causes a natural frequency drop.

Mechanical and physical characteristics of concrete mixed with sugarcane bagasse ash and recycled polyethylene terephthalate

The goal of this study was to produce sustainable concrete by reducing reliance on cement, which contributes to high carbon footprints, and natural sand, which is being depleted. Sugarcane bagasse ash (SCBA) was used to partially replace cement at 5 %, 10 %, and 15 %, while recycled polyethylene terephthalate (RPET) was used to partially replace sand at 5 %, 10 %, 15 %, and 20 %. The effects of these substitutions on concrete's mechanical and physical properties were examined after 28 days of water curing. The study observed a decrease in fresh density by 0.36 %–2.67 % with SCBA and RPET inclusion. The slump values ranged between 93 mm and 140 mm, indicating good workability. The reference concrete's compressive strength was 39.65 MPa, while the mix with 5 % SCBA and 10 % RPET achieved 38.23 MPa. This mix also showed a 1.2 % higher split tensile strength than the reference concrete. Although the reference concrete's flexural strength was the highest at 4.56 MPa, all SCBA-RPET mixes remained within 86 % of this value. All modified mixes weighed less than the reference concrete, with the compressive strength-to-weight ratio of the mix with 5 % SCBA and 10 % RPET being closest to the reference mix with only a 2.44 % reduction. These findings suggest that SCBA and RPET can be effectively used to produce sustainable concrete with comparable mechanical properties to conventional concrete.

Eco‐friendly synthesis of non‐isocyanate polyurea using PET and CO2 upcycling: A double green approach

AbstractFrom the perspective of sustainability, this research explored both the recycling of polyethylene terephthalate (PET) and the conversion of carbon dioxide (CO2) into polymer materials. To this end, a series of copolyurea specimens were synthesized through the polycondensation of carbon dioxide with hexamethylenediamine (HDA) and terephthalic dihydrazide (TDH), where TDH was derived from the chemical recycling of PET via the aminolysis method. FTIR spectroscopy, 1H NMR, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) characterized the products of PET recycling and synthesized copolyureas. Additionally, we sought to identify the optimal parameters for both the recycling and copolymerization processes. The results of identification analyses for both the recycling and copolymerization reactions confirmed the formation of the desired structures. An increase in the hard segment (TDH) led to discrepancies between the intended and actual monomer ratios in the synthesis, possibly due to dimethyl sulfoxide (DMSO) solubility issues or unreacted TDH. Furthermore, the TGA analysis indicated that the initial degradation temperature (Td,5%) of the copolymer increased with the proportion of aromatic rings in the hard segment, underscoring the complex interactions within the copolymer matrix affecting its thermal and structural properties. The DSC results revealed that for copolyureas with the formula HDAxTDH100–x (where x = 50, 60, 70, 80, 90), reducing the x fraction or increasing the TDH content lowered the melting temperature. Furthermore, at a high percentage of TDH, the melting point disappeared entirely due to the destruction of the crystalline structure, indicating a critical threshold where the copolymer transitions from a semi‐crystalline to an amorphous state.

Determination of Diffusion Coefficients of Bisphenol A (BPA) in Polyethylene Terephthalate (PET) to Estimate Migration of BPA from Recycled PET into Foods

Bisphenol A (BPA) is a known substance that is found in food contact materials as an intentionally added as well as a non-intentionally added substance. Traces of BPA were found as a non-intentionally added substance in recycled PET (rPET). In 2023, the EFSA proposed a new TDI of 0.0002 µg/kg bw/d, which is lower than the previous (temporary) TDI of 4 µg/kg bw/d by a factor of 20,000. The TDI of 0.0002 µg/kg bw/d would translate for a default 60 kg person eating one kilogram of food into a migration limit of 0.012 µg/kg in the food. This very low migration limit is a challenge to measuring BPA levels in food. A solution is to use migration modeling to establish maximum concentrations in rPET for different food contact applications. Precise diffusion coefficients for BPA in PET were determined within this study by use of migration kinetics. In June 2024, the European Commission proposed a new migration threshold limit for BPA of 1 µg/kg, which should be understood as a detection limit. From the results of this study, it can be concluded that a BPA concentration in the PET bottle wall of 297 mg/kg (3% acetic acid), 255 mg/kg (10% ethanol), and 192 mg/kg (20% ethanol) after storage for 365 d at 25 °C is in compliance with the migration threshold limit of 1 µg/kg. These maximum concentrations are far above the measured BPA concentrations on rPET bottles in Europe between 2019 and 2023. Therefore, the new proposed migration threshold limit for BPA cannot be exceeded.

Eco-friendly strain-hardening cementitious composites with recycled PET fine aggregate: Mechanical behavior and environmental benefits

The production of strain-hardening cementitious composites (SHCC) heavily relies on natural fine aggregates. This study employs recycled PET fine aggregates to prepare PET-modified SHCC (P-SHCC). The physical properties and mechanical behavior of P-SHCC with different PET volume replacement ratios (0 %, 25 %, 50 %, 75 %, and 100 %) are experimentally investigated. The microstructures were examined to analyze the impact of additional defects induced by the interfacial transition zone between recycled PET and cementitious matrix. The multiple cracking behavior was discussed based on the crack parameters. The results indicate that the incorporation of PET significantly enhances the ultimate strain and crack control capability of SHCC while reducing the material's density. Furthermore, energy consumption, carbon emission, and comprehensive environmental indexes were employed to analyze the environmental benefits. The findings demonstrate the feasibility of preparing SHCC with recycled PET fine aggregate, particularly in enhancing the strain capacity and environmental benefits.

A Promising Recycling Strategy via Processing Polypropylene/Recycled Poly(ethylene terephthalate): Reactive Extrusion Using Dual Compatibilizers.

Enhancing interfacial adhesion in polypropylene (PP)/recycled polyethylene terephthalate (rPET) blends is crucial for the effective mechanical recycling of these commercial plastic wastes. This study investigates the reactive extrusion of PP/rPET blends using a dual compatibilizer system comprising maleic anhydride grafted polypropylene (PP-g-MA) and various glycidyl methacrylate (GMA)-based compatibilizers. The effects of backbone structure and reactive group on the morphological, mechanical, and thermal characteristics were systematically studied. This study sheds light on the effective compatibilization mechanisms using characterization methods such as Fourier Transform Infrared Spectroscopy (FTIR) and morphological analyses (SEM). The results indicate that GMA-based compatibilizers play a bridging role between rPET and PP-g-MA, resulting in improved compatibility between the blend components. A combination of 3 phr PP-g-MA and 3 phr ethylene-methyl acrylate glycidyl methacrylate terpolymer (EMA-GMA) significantly improves interfacial adhesion, leading to synergistic enhancements of mechanical performance of the blend, up to 217% and 116% increases in elongation at break and impact strength, respectively, compared to the uncompatibilized sample. Moreover, a significant improvement in onset temperature for degradation is observed for the dual compatibilized sample, with 40 °C and 33 °C increases in onset temperature relative to the uncompatibilized and the single compatibilized samples. These findings underscore the immense potential of tailored multi-component compatibilizer systems for upgrading recycled plastic waste materials.

Development of Multi-Walled Carbon Nanotube-Integrated Recycled Polyethylene Terephthalate Electrospun Antibacterial Face Mask

In this study, electrospun nanofiber membranes were successfully fabricated by modifying recycled polyethylene terephthalate (r-PET) with multi-walled carbon nanotubes (MWCNTs) for face mask applications. The recycling of PET bottles ensures effective waste management, while the electrospinning process facilitates the creation of delicate nano-range fibers. The inclusion of MWCNTs aimed to assess the antibacterial activity of the resulting nanomembranes. The fabricated samples underwent comprehensive characterization, including scanning electron microscopy (SEM), ultimate tensile testing, particulate filtration efficiency (PFE) testing, Fourier transform infrared spectroscopy (FTIR), and antibacterial sensitivity assays, revealing significant findings. MWCNTs incorporation led to minor bead formation in the membranes, with fiber diameters ranging from 446 to 862 nm. However, MWCNTs resulted in reduced stiffness and tensile properties due to the disruption of polymer chain alignment. The nanofiber membranes demonstrated effective filtration of 0.3 µm particulates, achieving filtration rates between 96 to 97%Functional group analysis confirmed the presence of both r-PET and MWCNTs in the composites. Although the r-PET/MWCNTs 12 kV membrane lacked an antibacterial zone of inhibition, it exhibited reductions of 28.64% for S. aureus and 31.9% for E. coli. These results collectively underscore the potential of r-PET/MWCNTs samples as an alternative nanofibrous membrane material for face masks. J. of Sci. and Tech. Res. 5(1): 63-74, 2023

Advancing Analytical Techniques in PET and rPET: Development of an ICP-MS Method for the Analysis of Trace Metals and Rare Earth Elements.

Despite the extensive use of recycled polyethylene terephthalate (rPET) in food contact materials (FCMs), research on the presence of heavy metals (HMs) and rare earth elements (REEs) during various recycling stages (e.g., flakes, granules, and preforms) remains limited. This study aimed to address these gaps by validating a rapid and sensitive analytical method to quantify 26 HMs and 4 REEs in PET and rPET matrices. An ICP-MS method was validated per EURACHEM guidelines, assessing linearity, limits of detection (LOD), limits of quantification (LOQ), accuracy, and repeatability. The method was employed for initial screening of HMs and REEs classified as non-intentionally added substances (NIASs) in PET and rPET samples. The findings showed high accuracy and reliability, with recovery rates between 80% and 120%. Analysis revealed varying concentrations of HMs and REEs, with the highest levels in 100% rPET preforms, notably Zn, Cu, and Al among HMs, and La among REEs. The study identified critical contamination points during the recycling process, highlighting the need for targeted interventions. This research provides a crucial analytical framework for assessing HMs and REEs in PET and rPET, ensuring FCM safety compliance and supporting efforts to enhance rPET product safety, promoting public health protection and advancing the circular economy.

Cryogenic Insulation-Towards Environmentally Friendly Polyurethane Foams.

Cryogenics is the science and technology of very low temperatures, typically below 120 K. The most common applications are liquified natural gas carriers, ground-based tanks, and propellant tanks for space launchers. A crucial aspect of cryogenic technology is effective insulation to minimise boil-off from storage tanks and prevent frost build-up. Rigid closed-cell foams are prominent in various applications, including cryogenic insulation, due to their balance between thermal and mechanical properties. Polyurethane (PU) foam is widely used for internal insulation in cryogenic tanks, providing durability under thermal shocks and operational loads. External insulation, used in liquified natural gas carriers and ground-based tanks, generally demands less compressive strength and can utilise lower-density foams. The evolution of cryogenic insulation materials has seen the incorporation of environmentally friendly blowing agents and bio-based polyols to enhance sustainability. Fourth-generation physical blowing agents, such as HFO-1233zd(E) and HFO-1336mzz(Z), offer low global warming potential and improved thermal conductivity. Additionally, bio-based polyols from renewable resources like different natural oils and recycled polyethylene terephthalate (PET) are being integrated into rigid PU foams, showing promising properties for cryogenic applications. Research continues to optimise these materials for better mechanical performance and environmental impact.

Novel selection of recycled PET surrogates based on non-targeted screening of non-intentionally added substances and chemometrics

Waste PET is utilized to produce recycled PET (rPET) through bottle-to-bottle recycling in order to reduce environmental pollution. However, non-intentionally added substances (NIAS) may be generated during rPET production, potentially posing a threat to food safety. In this study, a non-target screening of 13 batches with a total of 39 rPET samples was performed using GC-QTOF-MS and 240 compounds were tentatively identified. It was worth noting that the detection of phthalate esters in rPET from China, such as bis(2-ethylhexyl) phthalate, exhibits a higher diversity (17 different types) and frequency (7.8 %–100 %) in comparison with related studies. Subsequently, based on the principles for selection of surrogates used in challenge test, seven molecular descriptors were selected as variables for compound characterization, followed by principal component analysis (PCA) for representation. Based on this analysis and referencing the EFSA and FDA surrogate suggestion lists, eight surrogates were proposed for China, namely chlorobenzene, toluene, benzophenone, bis(2-ethylhexyl) terephthalate, methyl salicylate, methyl stearate, 1-phenyldecane and phenylcyclohexane. High-throughput detection methods were developed for each surrogate with the regression correlation coefficients over 0.999, spiked recoveries ranging from 99.3-107.5 %, LODs of 0.003–2.192 ng/mL, LOQs of 0.009–7.306 ng/mL, RSD of 0.71–4.23 %, respectively. This research provides foundational data and methodological support for the evaluation of rPET challenge testing in China, offering technical support for subsequent safety assessments of rPET.

Predicting Dyeing Properties and Light Fastness Rating of Recycled PET by Artificial Neural Network

Predicting Dyeing Properties and Light Fastness Rating of Recycled PET by Artificial Neural Network