Repurposing polyethylene terephthalate plastic waste to capture carbon dioxide

Abstract

Polyethylene terephthalate (PET) is a ubiquitous polymer with a lack of viable waste management solutions besides mechanical recycling, incineration, and landfilling. Herein, we demonstrate a chemical upcycling of PET waste into materials for CO₂ capture via aminolysis. The aminolysis reaction products—a bis-aminoamide (BAETA) and oligomers—exhibit high CO₂ capture capacity up to 3.4 moles per kilogram as a stand-alone organic solid material. BAETA shows strong chemisorption featuring high selectivity for CO₂ capture from flue gas (5 to 20% CO₂) and ambient air (~400 parts per million CO₂) under humid conditions. Our thermally stable material (>250°C) enables CO₂ capture at high temperatures (up to 170°C) for multiple cycles. Scalability of the material production was demonstrated by performing aminolysis of untreated consumer waste PET of 1 kilogram. Our approach introduces a simple and straightforward solution that can address both plastic waste and carbon dioxide, offering a potential pathway toward net negative emissions.

A scalable chemical upcycling of PET waste into an efficient, durable, and selective CO₂ sorbent has been achieved.

INTRODUCTION

Polyethylene terephthalate (PET) is among the most widely produced plastics, with annual production reaching 70 million metric tons (Mt), accounting for 18% of global plastic output (1, 2). However, PET waste recycling is limited due to inadequate collection infrastructure, the complexity of sorting, and the lower market demand and economic viability of recycled PET compared to using virgin PET resin (1, 3). It is estimated that ~85 to 90% of produced PET is either incinerated to supply energy or landfilled, both of which pose environmental challenges and contribute to additional CO₂ emissions (4–7). Only a fraction—10 to 15%—of PET (8) is recycled, predominantly through mechanical (9, 10) and chemical methods (2, 11–13), yet the efficacy of these methods needs substantial improvement (14). Given the anticipated increase in PET and general plastic production and waste generation due to population growth (15), it is critical to explore alternative solutions beyond mechanical recycling, landfilling, and energy recovery (Fig. 1A).

Fig. 1. Repurposing PET plastic waste to capture carbon dioxide.

(A) PET life cycle and project motivation. (B) Alternative waste mitigation offering PET upcycling into scalable carbon capture materials [X = N(H) or O].

Upcycling of plastic waste is an emerging approach that can repurpose waste into functional applications (16). Therefore, chemical upcycling of PET waste into CO₂ capture materials can potentially address two urgent societal problems: accumulation of plastic waste and atmospheric CO₂ (17, 18). It has been estimated that carbon dioxide removal (CDR) should reach the capacity of 1.5 to 2.6 billion metric tons (Gt) annually to meet carbon neutrality by 2050 (19, 20). In this scenario, any useful CO₂-sorbent material must be produced, at least, in the order of million metric tons per year from cheap and abundant sources (21). Notably, the upcycling of PET waste for CO₂ capture has been explored by producing activated carbons via energy intensive pyrolysis (22–24) or by generating organic ligands for synthesizing metal-organic frameworks (25, 26).

By contrast, selective depolymerization reactions can offer the advantage of breaking down polymers into their corresponding monomers or modifying them into other valuable materials, allowing the creation of desired specific properties (3). Recently, we demonstrated catalytic depolymerization of polyesters under metal-free conditions using glycolysis (11). We envision that the utilization of aminolysis of PET (27–35) can provide a scalable, robust, cost-effective, and operationally simple process to access sorbents for capturing CO₂. Herein, we demonstrate the upcycling of postconsumer PET waste using low-cost 1,2-ethylenediamine (EN) into an organic molecular solid-state CO₂ sorbent, N¹,N⁴-bis(2-aminoethyl)terephthalamide (BAETA), and oligomers (OLs) via atom-economic aminolysis (Fig. 1B).

RESULTS

CO₂ sorbent synthesis from PET waste via aminolysis optimization

Amine-based sorbents are commonly used as an aqueous solution for carbon capture due to their relatively low energy requirements for regeneration [172 kJ/mol for 30 wt % monoethanolamine (MEA)] and high CO₂ sorption capacities (0.4 to 0.5 mol of CO₂ per mole of amine). However, one of the key limitations of MEA is associated with notable solvent loss at the absorber and degradation of the absorbent under thermal regeneration conditions into potentially toxic compounds for the environment (36). This leads to substantial operational costs for carbon capture for regenerating MEA. By incorporating diamine moieties within the terephthalic scaffold, we aimed to address the drawbacks associated with small amine-based aqueous sorbents, including, for example, MEA’s low boiling point (116°C), thermal stability (<120°C) (37), high vapor pressure (2.13 kPa at 25°C), volatility (38), corrosiveness, and environmental toxicity (39).

EN was selected for the purpose of selective depolymerization of PET, owing to its high reactivity toward PET and high CO₂ capture capacity (40, 41). As the general source of PET, drinking bottles were used with minimal pretreatment that only included cutting and rinsing with water (see Supplementary Materials, Section 2.1). Building on the known PET aminolysis reactions (27–35), we optimized the depolymerization conditions to access the monomer BAETA and related OLs by using minimal amounts of EN relative to PET (Fig. 2, A and B). This provides atom-economical reaction conditions with high yields of the desired products. The reaction was performed either at 60°C under stirring for 24 hours or at room temperature over a period of up to 2 weeks. BAETA was obtained in up to 60% yield, along with OLs (<40%). BAETA can be separated from OLs through hot filtration, as it dissolves in hot methanol or hot water, whereas OLs are insoluble (see Supplementary Materials, Section 2). Notably, the reaction by-product ethylene glycol can be collected via distillation (Supplementary Materials, Section 2.3).

Fig. 2. PET waste upcycling into solid CO₂ sorbents via aminolysis.

(A) PET aminolysis in the literature. TBD, 1,5,7-triazabicyclo[4.4.0]dec-5-ene. (B) Reaction scheme for PET aminolysis using EN under optimized conditions. (C) PET sources used in the aminolysis reaction, including drinking bottles, food packaging, stuffing materials for toys, and textiles, along with the resulting yields of BAETA + OLs. (D) Scale-up of the PET aminolysis reaction to 1 kg of PET substrate using 2 molar equiv of EN at room temperature. r.t., room temperature. (E) Selective PET aminolysis reaction performed by mixing PET with common household waste materials.

Scale-up and PET waste-stream scope

We then tested various sources of postconsumer PET waste such as PET bottles, PET fibers, PET food packaging, and PET textiles, which were smoothly converted into BAETA (Fig. 2C). We also scaled up the depolymerization using 1 kg of untreated end-of-use consumer PET waste affording 800 g of products—BAETA-OL mixture after simple purification (Fig. 2D). Considering the diverse range of PET to be recycled directly from the postconsumer waste stream, we applied our aminolysis procedure to a mixture of waste, including food packaging (100% PET), food waste (chili mayo), disposable cups (100% polystyrene), paper (100% cellulose), aluminum foil, disposable laboratory gloves (100% nitrile butadiene rubber), wrapping film (100% polyethylene), and cotton balls (Fig. 2E). The results showed only a slight decrease in the yield of BAETA (38%) while conserving other unreacted wastes, showcasing the applicability and robustness of our depolymerization process.

BAETA sorbent thermal stability and comparison with other amines

After establishing a procedure for accessing BAETA, the initial analyses were focused on its thermal stability and CO₂ capture performance. BAETA demonstrated stability up to 220°C (fig. S2) under air, with decomposition beginning around 250°C. Thermogravimetric analyses (TGAs) of OLs presented a similar profile to BAETA, with a higher temperature (300°C; fig. S3) required for full decomposition. Both BAETA and OLs can withstand temperatures up to 250°C in CO₂, N₂, and compressed air, as detailed in Supplementary Materials, Section 2.6. Thus, BAETA and OLs could, in principle, be applied in flue gas CO₂ capture processes at high temperatures (120° to 150°C). This was further confirmed by testing the stability of BAETA in comparison with common amine sorbents such as MEA, by independently preparing sorbent-CO₂ adducts and subjecting them to thermal decomposition conditions (Fig. 3A). The BAETA-CO₂ adduct showed exceptionally high thermal stability compared to all tested CO₂ adducts. BAETA releases CO₂ only after 150°C and remains stable until 250°C, followed by oligomerization (releasing 1 equiv of diamine to form a dimer and OLs; see fig. S58). In contrast, other amine sorbents showed complete evaporation and decomposition at temperatures around 100°C. These results indicate that BAETA offers superior thermal stability as a pure organic compound, making it a suitable and effective solid sorbent for CO₂ capture applications without requiring additional support or solvent.

Fig. 3. Stability and CO₂ capture performances of BAETA and OLs.

(A) Thermal stability of the BAETA-CO₂ adduct compared with diamine-CO₂ adducts under a 100% N₂ flow of 90 ml/min, heating rate: 1°C/min. (B) CO₂ uptake profile of BAETA at various temperatures; 90 ml/min, 100% CO₂ flow. (C) CO₂ uptake at 150°C under simulated flue gas conditions (15% CO₂ + compressed air: 78% nitrogen, 21% oxygen, ~1% argon, and trace gases like CO₂). (D) Oxidative stability of BAETA and its CO₂ capture performance after repeated exposure to air at 100°C; CO₂ capture performed at 150°C, 90 ml/min, 100% CO₂ flow for sorption and 100% N₂ for desorption. (E) Recyclability profile at 150°C, 90 ml/min, flow of 15% CO₂ + 85% N₂ for sorption and 100% N₂ for desorption. (F) CO₂ uptake using pelletized BAETA (at 150°C, 90 ml/min, 15% CO₂ + 85% N₂ flow for sorption and 100% N₂ for desorption). (G) CO₂ absorption at r.t. under 1 atm CO₂ at different RH levels. (H) DAC performance at 75% RH and r.t. Blue: CO₂ concentration in air before the capture column; purple: CO₂ concentration of the processed air after the BAETA filter.

CO₂ capture at elevated temperature and flue gas application

After confirming the thermal stability of BAETA, we evaluated BAETA in terms of gravimetric CO₂ uptake performance at various temperatures. Enhanced performance of CO₂ uptake was observed at elevated temperatures, with the highest gravimetric uptake observed at 150°C [15 wt % for BAETA (Fig. 3B) and 3.8 wt % for OLs (fig. S12)]. Kinetic studies showed an activation energy of 150 kJ/mol for BAETA (Supplementary Materials, Section 4.5), consistent with its observed CO₂ capture behavior, suggesting chemisorption to form a carbamate. This result shows that BAETA has a higher energy requirement for CO₂ capture at equilibrium compared to other amine-based solvents, which typically have a heat of absorption around 80 to 100 kJ/mol (42). The high activation energy of BAETA implies slower CO₂ capture at a low temperature. However, more stable adduct formation is plausible, suggesting enhanced selectivity for CO₂ capture and reliable performance under elevated temperatures of flue gas. Further investigations into the CO₂ capture capabilities of BAETA under flue gas conditions (using 5 to 10% CO₂ in N₂ flow) revealed that the rate and capacity of CO₂ absorption decreased only a small fraction, achieving up to 11 to 13 wt % CO₂ uptake (Fig. 3C and fig. S15). BAETA showed comparable CO₂ uptake performance with a gas mixture of 15% CO₂ and 85% synthetic air at 120° to 150°C (Fig. 3C, blue curve, and fig. S18).

Oxidative stress and durability over multiple thermal treatment cycles

Amine-based sorbents are prone to oxidative degradation due to prolonged exposure to oxygen, heat, and impurities in flue gases. Amine-functionalized resins, such as commercial Lewatit resin, tend to be more stable than MEA-based liquid amines; however, they still suffer from oxidative degradation (43–47). To demonstrate the potential applications of BAETA in flue gas treatment and direct air capture (DAC), its oxidative stability was tested by exposing BAETA to air at 100°C for 60 min, followed by a CO₂ capture cycle at 150°C (Fig. 3D and fig. S22A). The performance was then compared with commercial Lewatit resin (fig. S22B). As shown in Fig. 3D and fig. S22A, BAETA retains its CO₂ capture and release performance after exposure to air at 100°C for 60 min, maintaining a constant CO₂ uptake of 14 wt % over five cycles. In contrast, Lewatit (fig. S22B) initially captures only 2.25 wt % CO₂, and its performance deteriorates after each exposure to hot air, reaching a CO₂ uptake of only 1.7 wt % by the fifth cycle. This demonstrates the remarkable thermal and oxidative stability of BAETA.

Because of its demonstrated efficiency after repeated oxidative stress at high temperatures, we continued investigating the durability of BAETA under flue gas conditions by performing 40 consecutive cycles of CO₂ capture and desorption at an elevated temperature (150°C). A gas mixture comprising 15% CO₂ and 85% N₂ was selected for the absorption phase (30 min), and a 100% N₂ flow (20 min) was used for the desorption step. Over this range of 40 cycles at a constant temperature of 150°C, the CO₂ capture capacity of BAETA exhibited no detectable decrease, indicating the effectiveness of BAETA as a recyclable and durable CO₂ sorbent (Fig. 3E). To further illustrate the processability of BAETA, a pelletization test was performed without any additional binders, providing pellets with comparable CO₂ capture capacity to the original powder form (Fig. 3F).

After subjecting BAETA to repeated thermal treatment cycles, a gradual decrease in CO₂ capture efficiency was observed due to oligomerization via transamidation occurring under CO₂ capture cycling conditions of Fig. 3E (150°C with a N₂ flow of 90 ml/min). A by-product of the transamidation is EN, which is released during oligomerization. However, the presence of CO₂ stabilizes the material and prevents this oligomerization (fig. S19). To ensure long-term stability of BAETA, optimizing the thermal treatment cycling rate and duration will be necessary to maintain BAETA’s sorption capacity. In this context, the desorption time was adjusted and optimized to ensure that a small amount of CO₂ remains on the sorbent, leading to optimized conditions and recycling experiments up to 150 cycles, which balances regeneration while maintaining stability (see Supplementary Materials, Section 3.6 and fig. S16).

Carbon capture at different relative humidity levels and direct air capture application

Because the resulting CO₂ adducts of BAETA showed remarkable stability, we presumed that a carbon capture process can be spontaneous even at low CO₂ concentrations (47). Although BAETA showed no CO₂ uptake at low temperatures under our experimental conditions, the exposure of BAETA at room temperature to ambient laboratory air showed notable CO₂ uptake (Supplementary Materials, Sections 3.2 and 3.3). It is believed that water lowers the energy barrier for CO₂ capture directly from the air, thereby facilitating the formation of carbamate and/or bicarbonate salts assisted by ambient humidity (48, 49). Therefore, we tested the impact of humidity for BAETA and OLs in carbon capture by modulating the relative humidity (RH), ranging from 0 to 100% RH, at 25°C from 1 atm CO₂ for 7 days (Fig. 3G and Supplementary Materials, Section 3.12). BAETA and OLs both showed an increase in CO₂ capture capacity as the humidity level increases. Notably, lower capacity (4 to 6 wt %) was observed at lower humidity levels than 50% RH, whereas the highest CO₂ capture capacity was observed at a high RH (up to 12 wt %).

The application potential in DAC was evaluated with a continuous CO₂ capture experimental setup (figs. S28 and S29) with a filter containing BAETA (1.5 g) at a continuous airflow of 5.4 ml/min at room temperature. The RH was monitored and maintained at 75% to promote DAC. It was observed that BAETA was capable of purifying air to sequestrate CO₂ for more than 13 days (Fig. 3H), resulting in 83 liters of air processed and 0.063 g of CO₂ captured with a capture efficiency of 88% based on the total CO₂ passed through the column that was determined by reference CO₂ sensor (no BAETA filtration, blue plot) and compared with CO₂ concentration data after BAETA DAC filter (see experimental details in Supplementary Materials, Section 3.11).

Thermodynamic properties of BAETA

The thermal properties of BAETA were determined by conducting calorimetry (25 mM aqueous sorbent solution at 25°C; Supplementary Materials, Section 4.4), providing a heat of absorption of −37.2 kJ/mol (first equivalent of CO₂) and −33.6 kJ/mol (second equivalent of CO₂). When compared with benchmark systems (e.g., MEA: −37.4 kJ/mol and EN: −39.7 kJ/mol under identical conditions), the heat of absorption of BAETA is close to MEA. For BAETA in solid form, up to 130° to 140°C or heating was required to fully desorb CO₂ from BAETA under reduced pressure (~5 mmHg). It is noteworthy here that BAETA showed high thermal stability in boiling water under air, implying the possibility of using steam for the desorption step (Supplementary Materials, Section 3.14). Owing to the exceptional water, heat, and oxidation stability of BAETA, the use of boiling water was sufficient to desorb >99% CO₂ within 20 min in a preliminary test (12.5 mM BAETA in 6 ml of D₂O).

Structural changes during CO₂ sorption determined by solid-state NMR and electron diffraction

Our PET-derived CO₂ sorbent, BAETA, is most effective for CO₂ capture as a solid, without the need for dissolution or additional solid support. Therefore, we used solid-state analysis techniques: Fourier transform infrared (FTIR) spectroscopy, solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and three-dimensional electron diffraction (3D ED) on the BAETA-CO₂ adduct to elucidate the high thermal stability of the CO₂ adduct and the CO₂ uptake mechanism. The BAETA-CO₂ adduct was directly obtained from our standard CO₂ capture and DAC conditions (Fig. 4A). Infrared spectra indicate additional peaks (1579 and 1444 cm⁻¹ of C═O stretch and 3322 cm⁻¹ N─H stretch from carbamate) after CO₂ treatment regardless of CO₂ capture conditions using concentrated or diluted CO₂ (Fig. 4B). Further structural studies of the BAETA-CO₂ by solid-state ¹³C and ¹⁵N cross-polarization/MAS NMR (CP/MAS NMR) spectroscopy verified the nature of the CO₂ capture (Fig. 4C, blue and magenta: before and after CO₂ exposure, respectively). After CO₂ uptake, a new species was obtained, which was assigned to ammonium carbamate (50–52) with an unsymmetrical structure. This is confirmed by ¹³C solid-state NMR (ss-NMR), where a new C═O peak at 164 parts per million (ppm) appears after CO₂ sorption, indicating carbamate formation. In addition, the original C═O peak from the BAETA amide bond splits into two distinct signals, suggesting an asymmetrical molecule where one amine group binds CO₂ as carbamate whereas the other is protonated. Further evidence from ¹⁵N ss-NMR supports this structure, with peaks at 32 ppm (R─NH₃⁺) and 85 ppm (R─NHCO₂⁻), as well as a new amide peak at 110 ppm. The complete disappearance of the original amine peak at 22 ppm confirms that all BAETA molecules undergo quantitative conversion to BAETA-CO₂. The use of ¹³C-labeled CO₂ further verifies the chemisorption mechanism, where the intense 164 ppm C═O peak provides direct evidence of carbamate formation (Fig. 4C). The observed peak differentiation before and after CO₂ capture follows the same pattern regardless of the sorption conditions (whether thermally induced or humidity driven), indicating a uniform structural transformation upon CO₂ capture (for full ss-NMR spectra, see Supplementary Materials, Section 4.3).

Fig. 4. Structural changes of BAETA during CO₂ absorption.

(A) Proposed carbamate formation reaction of BAETA under CO₂ capture conditions. (B) FTIR spectra of BAETA: after DAC (burgundy), after thermal CO₂ capture at 150°C (purple), and lean BAETA (blue). (C) Solid-state ¹⁵N and ¹³C (carbonyl region only) CP/MAS NMR spectra of BAETA (blue) and BAETA-CO₂ (magenta) using ¹H-¹⁵N CP (left), ¹H-¹³C CP (middle), and ¹H-¹³C CP with ¹³C-labeled CO₂ (right); full spectra in Supplementary Materials, Section 4.3. (D) Structure of BAETA-CO₂ obtained by ED. Green lines between nitrogen and oxygen atoms indicates distances of hydrogen bonding (N─H···O) and are measured to be between 2.7 and 2.9 Å.

DISCUSSION

The chemical structure of this stable carbamate species was unambiguously determined by solving the crystal structure via ED (Supplementary Materials, Section 4.2). The molecule is asymmetric, with an ammonium group on one side and the carbamate on the other side, stabilized by four hydrogen bond donors by neighboring molecules (Fig. 4D). We hypothesize that the amide hydrogen bonding donors/acceptors of BAETA are crucial for the observed thermal and chemical stability of BAETA-CO₂, as illustrated in many examples in amide-based organic materials (53, 54). To support our hypothesis that hydrogen bonding is crucial for CO₂ capture at high temperatures, we synthesized a modified BAETA derivative where the two secondary amide groups were methylated to tertiary amides (Supplementary Materials, Section 6). This N-methylated BAETA (N-Me-BAETA) showed a maximum uptake of CO₂ only up to 2.5 wt % at 150°C under 100% CO₂ conditions, compared to 13 wt % CO₂ uptake for BAETA under identical conditions (fig. S63). Although the thermal stability profiles were similar (fig. S2 for BAETA and fig. S62 for N-Me-BAETA), the methylated derivative showed degradation based on the NMR spectroscopic analysis after CO₂ exposure (fig. S64). These findings highlight the critical role of secondary amide functional groups in the high-temperature CO₂ capture and overall performance of BAETA.

Although the high stability of ammonium carbamate of BAETA implies high CO₂ uptake at high temperatures, regeneration of BAETA with high thermal energy is also apparent. However, lower regeneration temperatures of our sorbents can be aided by pressure swing desorption and by using steam for large scale deployment (55, 56), as shown in a preliminary test with continuous carbon capture and desorption experiments using heated humid air (120° to 135°C; fig. S36). Depolymerization of PET using various amine nucleophiles offers an avenue to explore thermally stable organic amide-based materials. This approach addresses the limitations of small organic molecules for carbon capture—thermal decomposition and evaporative amine-solvent loss (57)—thus opening possibilities for CO₂ capture at higher temperatures, which is crucial for industrial exhaust stream treatment (58). Nevertheless, it potentially provides an alternative and holistic solution to mitigate single-use plastic waste accumulation, by enhancing the value of end-of-life PET through an atom-economic upcycling process for scalable carbon dioxide capture.

MATERIALS AND METHODS

All chemicals, unless explicitly specified, were sourced from commercial suppliers and used as received. Carbon dioxide (CO₂) was used directly from a cylinder with a purity of 99.7%, without any further treatment for reactions. The solvents used were HPLC (high-performance liquid chromatography) grade. Analytical TLC (thin-layer chromatography) was conducted on precoated Merck DC-Alufolien SiO₂ 60 F254 TLC plates, which had a thickness of 0.2 mm. Liquid-state ¹H and ¹³C NMR spectra were recorded at 500 and 126 MHz, respectively, on a Bruker Avance III spectrometer equipped with a Broad Band Fluorine–Observe (BBFO) probe. Chemical shifts (δ) were reported in parts per million (ppm), and coupling constants (J) were expressed in Hertz (Hz). The notation for NMR multiplicity included s (singlet), bs (broad singlet), d (doublet), t (triplet), q (quartet), and m (multiplet). All ss-NMR analyses of natural abundance samples were performed at 16.4 T on a Bruker Avance II spectrometer equipped with a 4-mm HXY MAS probe at a 12-kHz MAS rate. Carbon spectra (¹H-¹³C CP) were acquired with 1024 scans, a relaxation delay of 2.5 s, and an acquisition time of 50 ms. Nitrogen spectra (¹H-¹⁵N CP) were acquired with 78,000 scans, a repetition delay of 3 s, and an acquisition time of 25 ms. For both, the CP was optimized on U-¹³C,¹⁵N l-alanine with a 30% ramp on the ¹³C or ¹⁵N radio frequency (rf) channel, respectively. Spinal64 was used for ¹H decoupling during acquisition with an rf field strength of 100 kHz. The BAETA-¹³CO₂ complex was analyzed at 16.4 T (700 MHz for ¹H) on a Bruker Avance III HD spectrometer equipped with a 1.3-mm HCND probe at a 60-kHz MAS rate. A carbon spectrum (¹H-¹³C CP) was acquired with 12.288 scans, a repetition delay of 3 s, and an acquisition time of 15 ms. The CP was optimized on U-¹³C,¹⁵N l-alanine with a 30% ramp on the ¹³C rf channel. Spinal64 was used for ¹H decoupling during acquisition with an rf field strength of 142 kHz. Chemical shifts were calibrated indirectly through the adamantane peak observed at a low frequency (29.5 ppm relative to tetramethylsilane). FTIR spectra were recorded using a Bruker ALPHA-P FTIR spectrometer with a single-reflection attenuated total reflection (ATR) module. Electron microscopy images and 3D ED measurements were performed on a Rigaku XtaLAB Synergy-ED (59), equipped with a LaB₆ source operating at 200 kV (λ = 0.0251 Å). Heat of absorption and reaction rate constants were determined by conducting calorimetry experiments using a heat flow instrument (TAM 2277, TA Instruments, New Castle, DE, USA). EN was obtained from Sigma-Aldrich. Drinking bottles were collected directly from end users. TGA was conducted using a Discovery TGA instrument from TA Instruments (New Castle, DE, USA). The samples were subjected to a constant nitrogen flow of 25 ml/min and heated in platinum TGA pans from room temperature to 600°C at a heating rate of 10°C/min. TGA results were analyzed to determine the thermal decomposition and the first derivative of TGA (dTGA) temperatures of the samples, using Trios v5.1.1.46572 software from TA Instruments. Differential scanning calorimetry (DSC) analysis was carried out using a Discovery DSC instrument from TA Instruments (New Castle, USA). Samples weighing 4 to 5 mg were placed in Tzero aluminum pans with a perforated lid. Analyses were conducted under a nitrogen flow of 50 ml/min, with a linear heating rate of 10°C/min from 30° to 300°C.

Supplementary Materials

This PDF file includes:

Supplementary Text

Tables S1 to S14

Figs. S1 to S64

References