Value-Added Use of Waste PET in Rubberized Asphalt Materials for Sustainable Pavement

Waste poly(ethylene terephthalate) (PET) drinking bottles and end-of-life scrap rubber tires are common municipal solid wastes discarded and produced every day, which are usually disposed of in landfills and stockpiles, occupying a great quantity of land and causing serious environmental issues. This study aims to first turn waste PET into two value-added derived additives under the chemical treatment of two amines, namely triethylenetetramine (TETA) and ethanolamine (EA), respectively, and then adopt them in association with crumb rubber (CR) to modify virgin bitumen for preparing various rubberized asphalt mixtures. Subsequently, the high- and low-temperature properties of the rubberized binder modified by PET additives (PET-TETA and PET-EA) were comparatively characterized through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, while the rutting resistance, fatigue resistance, and dynamic modulus of the further fabricated mixtures were evaluated and validated through mixture tests. The results obtained indicate that 2 wt.% PET-TETA and PET-EA contribute to increase the rutting failure temperature of asphalt rubber from 82.2 °C to 85.5 °C and 84.2 °C, respectively, retaining the high grade of PG 82; the low-temperature grade of asphalt rubber slightly decreased from PG-28 to PG-22 as the additive was added; the rut depth slightly changed from 3.10 mm to nearly 3.70 mm; and PET-TETA exhibits the potential to be capable of extending the fatigue life of asphalt rubber in contrast with PET-EA at different stress levels within 450 kPa. Based on the findings of this study, the developed recycling approach is considered to be applicable to not only alleviate the environmental concerns caused by the landfills and stockpiles of those wastes but also make them valuable for building more durable pavement.

Synthesis of High Performance Thiophene–Aromatic Polyesters from Bio-Sourced Organic Acids and Polysaccharide-Derived Diol: Characterization and Degradability Studies

In this work, the feasibility of replacing petroleum-based poly(ethylene terephthalate) (PET) with fully bio-based copolyesters derived from dimethyl 2,5-thiophenedicarboxylate (DMTD), dimethyl 2,5-dimethoxyterephthalate (DMDMT), and polysaccharide-derived 1,6-hexanediol (HDO) was investigated. A systematic study of structure-property relationship revealed that the properties of these poly(thiophene–aromatic) copolyesters (PHS(20–90)) can be tailored by varying the ratio of diester monomers in the reaction, whereby an increase in DMTD content noticeably shortened the reaction time in the transesterification step due to its higher reactivity as compared with DMDMT. The copolyesters had weight-average molar masses (Mw) between 27,500 and 38,800 g/mol, and dispersity Đ of 2.0–2.5. The different polarity and stability of heterocyclic DMTD provided an efficient mean to tailor the crystallization ability of the copolyesters, which in turn affected the thermal and mechanical performance. The glass transition temperature (Tg) could be tuned from 70–100 °C, while the tensile strength was in a range of 23–80 MPa. The obtained results confirmed that the co-monomers were successfully inserted into the copolyester chains. As compared with commercial poly(ethylene terephthalate), the copolyesters displayed not only enhanced susceptibility to hydrolysis, but also appreciable biodegradability by lipases, with weight losses of up to 16% by weight after 28 weeks of incubation.

Efficient glycolysis of PET catalyzed by a metal-free phosphazene base: the important role of EG-

Developing efficient metal-free catalyst for the glycolysis of waste poly(ethylene terephthalate) (PET) with ethylene glycol (EG) has attracted increasing attention due to the demanding require for high-quality monomer used in...

An Efficient Protein Evolution Workflow for the Improvement of Bacterial PET Hydrolyzing Enzymes

Enzymatic degradation is a promising green approach to bioremediation and recycling of the polymer poly(ethylene terephthalate) (PET). In the past few years, several PET-hydrolysing enzymes (PHEs) have been discovered, and new variants have been evolved by protein engineering. Here, we report on a straightforward workflow employing semi-rational protein engineering combined to a high-throughput screening of variant libraries for their activity on PET nanoparticles. Using this approach, starting from the double variant W159H/S238F of Ideonella sakaiensis 201-F6 PETase, the W159H/F238A-ΔIsPET variant, possessing a higher hydrolytic activity on PET, was identified. This variant was stabilized by introducing two additional known substitutions (S121E and D186H) generating the TS-ΔIsPET variant. By using 0.1 mg mL−1 of TS-ΔIsPET, ~10.6 mM of degradation products were produced in 2 days from 9 mg mL−1 PET microparticles (~26% depolymerization yield). Indeed, TS-ΔIsPET allowed a massive degradation of PET nanoparticles (>80% depolymerization yield) in 1.5 h using only 20 μg of enzyme mL−1. The rationale underlying the effect on the catalytic parameters due to the F238A substitution was studied by enzymatic investigation and molecular dynamics/docking analysis. The present workflow is a well-suited protocol for the evolution of PHEs to help generate an efficient enzymatic toolbox for polyester degradation.

Analysis of Triboelectrostatic Separation Process of Mixed Poly(ethylene terephthalate) and High-Density Polyethylene

The aim of this study was to investigate and analyze the separation process of poly (ethylene terephthalate) and high-density polyethylene mixture. The research studied the influence of parameters of tribocharging and separation processes on the quality of separation. The research was carried out using a developed test stand consisting of a test tribocharger and a dedicated drum-type electrostatic separator. Both the separator and the tribocharger have been designed as automated test benches to assess the quality of plastic separation. In order to assess the quality of electrostatic separation of plastics, an original method based on the use of a dedicated vision system was used. The research was conducted in two stages. Firstly, the influence of the tribocharging process parameters on the efficiency of the process, i.e., the charge collected, was investigated. The next stage of the research was focused on the analysis of the influence of the separation process parameters on its effectiveness. The obtained results were presented and discussed. On the basis of the conducted research, the parameters of the tribocharging and separation processes affecting their effectiveness were determined.

Two Stages Thermal and Catalytic Cracking of Polyethylene Terephthalate to Fuel Production

PET (polyethylene terephthalate) is made up of polymerized repeating units of the ethylene terephthalate monomer (C10H8O4). PET is a recyclable plastic with the number 1 as its identification code. PET, which has a molecular weight of 192 gm/mole and contains 62.5 percent carbon, 33.3 percent oxygen, and 4.2 percent hydrogen, is utilized as synthetic fiber, polyester, plastic packaging, and soft drink containers all over the world. The main purpose of this study is to convert PET waste into liquid hydrocarbon fuel. Because PET use has risen significantly over the world, and the bulk of garbage is thrown into the soil rather than recycled, posing an environmental risk. During the heat breakdown phase, PET decomposes. It creates very strong and solid non-biodegradable terephthalic acid and benzoic acid complexes. To obtain liquid hydrocarbon fuel from PET, at 250-300℃, calcium hydroxide Ca(OH)2 is used as a catalyst in this study.