Study of the glycolysis of PET by oligoesters

Production of Novel Dental Resin Monomers Using Dimethacrylated Oligoesters Derived from Chemically Recycling PET Waste

This research explores the potential exploitation of recycled PET bottles in developing dimethacrylated oligoesters to be used as alternative monomers to produce novel dimethacrylate-based dental resins. Specifically, oligoester diols derived from PET glycolysis were converted into dimethacrylated oligoesters (PET-GLY-DMs), as alternative monomers to Bisphenol-A glycidyl methacrylate (Bis-GMA). The glycolysis products were analyzed for their molecular weight using Gel Permeation Chromatography (GPC) and the successful conversion of hydroxyl to methacrylate groups via methacrylation was confirmed by FT-IR spectroscopy. A gradient substitute of Bis-GMA by PET-GLY-DM within Bis-GMA/TEGDMA mixtures was conducted, and the gained dimethacrylated matrices were light-cured followed by the evaluation of their physicochemical and mechanical properties. It was revealed that the newly synthesized resins exhibited lower viscosity, higher degree of conversion, and reduced mechanical properties compared to the control resins. However, the most important observation, related to environmental friendliness, was that the PET-GLY-DMs did not release Bisphenol-A, as measured by liquid chromatography. The proportions of PET-GLY-DMs, Bis-GMA, and TEGDMA in dental resin formulations were optimized to achieve similar handling properties to control resins while maintaining significant hardening and mechanical performance. This research highlights the sustainability of the chemical recycling of PET, in the synthesis of novel products with added environmental and economic benefit.

More Efficient Chemical Recycling of Poly(Ethylene Terephthalate) by Intercepting Intermediates

The research presented in this paper offers insight into the availability of intermediates in the depolymerization of polyethylene terephthalate (PET) to be used as feedstock to create value-added products. Monitoring the dispersity, molecular weight, end groups, and crystallinity of reaction intermediates during the heterogeneous depolymerization of PET offers insight into the mechanism by which the polymer chains evolve during the reaction. Our results show dispersity decreases and crystallinity increases while the yield of insoluble PET remains high early in the reaction. Our interpretation of this data depicts a mechanism where chain scission targets amorphous tie chains between crystalline phases. Targeting the tie-chains lowers the Mn of the polymer without changing the amount of recovered polymer flake. Chain scission of tie-chains and isolating highly crystalline PET lowers the dispersity (Đ) of the polymer chains, as the size of the crystalline lamellae guides the molecular weight of the depolymerized oligomers. When sufficient end groups of PET chains are converted to alcohol groups, the PET flakes break apart into highly crystalline and less disperse polymer. Our results also demonstrate that the oligomeric depolymerization intermediates are readily repolymerized, offering new opportunities to chemically recycle PET more effectively and efficiently, from both an energy and purification standpoint.

Preparation and characterization of water-reducible polyester resin based on waste PET for insulation varnish

Water-reducible polyester resin (WRPE) for insulation varnish was prepared from waste polyethylene terephthalate (PET), glycerol (GL), and phthalic anhydride (PA) via depolymerization and condensation. PET was depolymerized via glycolysis at different molar ratios of PET/GL (PET repeating unit/GL molar ratios: 1.6, 1.3, and 1.0) with zinc acetate as a catalyst at 220-230 °C. The resulting glycolytic products (GPs) were reacted with PA at contents of 5, 7.5, 10, 12.5, and 15 wt%, based on the total weight. The prepared WRPEs were dissolved in phenol, neutralized with aqueous ammonia to pH = 7-7.5, and diluted in water. The WRPEs were cured with hexamethoxymethyl melamine resin (HMMM, WRPE : HMMM = 70 : 30, based on the dry mass) at 140 °C for 2 h. The formation of GPs, WRPE, and WRPE-HMMM was investigated using Fourier transformer infrared spectroscopy and proton nuclear magnetic resonance spectroscopy; the thermal properties were characterized using thermogravimetric analysis and differential scanning calorimetry. The electrical insulation strength and volume resistivity of the cured films with PA content were investigated. This strength and volume resistivity first increased with increasing PA content and then decreased above 10 wt%. The results show that WRPE with a PA content of 10 wt% exhibits optimal insulation properties.

Synthesis and characterization of novel acrylamide derivatives and their use as corrosion inhibitors for carbon steel in hydrochloric acid solution

Two new acrylamide derivatives were prepared namely: "N-(bis(2-hydroxyethyl) carbamothioyl) acrylamide (BHCA) and N-((2-hydroxyethyl) carbamothioyl) acrylamide( HCA) and their chemical structures were analyzed and confirmed using IR and 1H NMR". These chemicals were investigated as corrosion inhibitors for carbon steel (CS) in 1 M HCl medium using chemical method (mass  loss, ML), and electrochemical techniques including potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The results showed that the acrylamide derivatives work well as corrosion inhibitors, with inhibition efficacy (%IE) reaching 94.91-95.28% at 60 ppm for BHCA and HCA, respectively. Their inhibition depends mainly on their concentration and temperature of the solution. According to the PDP files, these derivatives function as mixed-type inhibitors that physically adsorb on the CS surface in accordance with the Langmuir adsorption isotherm, creating a thin coating that shields the CS surface from corrosive fluids. The charge transfer resistance (R_ct) increased and the double layer capacitance (C_dl) decreased as a result of the adsorption of the used derivatives. Calculated and described were the thermodynamic parameters for activation and adsorption. Quantum chemistry computations and Monte Carlo simulations were examined and discussed for these derivatives under investigation. Surface analysis was checked using atomic force microscope (AFM). Validity of the obtained data was demonstrated by the confirmation of these several independent procedures.

Unsaturated Polyester Resin Nanocomposites Based on Post-Consumer Polyethylene Terephthalate

A method for producing nanocomposites of unsaturated polyester resins (UPR) based on recycled polyethylene terephthalate (PET) as a matrix has been proposed. The upcycling method involves three successive stages: (1) oligoesters synthesis, (2) simultaneous glycolysis and interchain exchange of oligoesters with PET, (3) interaction of the obtained resins with glycol and maleic anhydride. UPRs were characterized by FTIR spectroscopy and gel permeation chromatography. The mechanical properties of nanocomposites obtained on the basis of these resins and titanium dioxide have been investigated. It has been shown that 1,2-propylene glycol units, despite their lower reactivity, significantly improve the properties of UPR. The most promising nanocomposite sample exhibited tensile strength 112.62 MPa, elongation at break 157.94%, and Young's modulus 29.95 MPa. These results indicate that the proposed method made it possible to obtain nanocomposites with high mechanical properties based on recycled PET thus allowing one to create a valuable product from waste.

Mechanistic aspects of poly(ethylene terephthalate) recycling-toward enabling high quality sustainability decisions in waste management

Since plastic waste pollution is a severe environmental concern in modern life, the demand for recycling poly(ethylene terephthalate) (PET) has increased due to its versatile applications. Taking advantage of plastic recycling methods creates the chances of minimizing overall crude oil-based materials consumption, and as a result, greenhouse gasses, specifically CO₂, will be decreased. Although many review articles have been published on plastic recycling methods from different aspects, a few review articles exist to investigate the organic reaction mechanism in plastic recycling. This review aims to describe other processes for recycling bottle waste of PET, considering the reaction mechanism. Understanding the reaction mechanism offers practical solutions toward protecting the environment against disadvantageous outgrowths rising from PET wastes. PET recycling aims to transform into a monomer/oligomer to produce new materials from plastic wastes. It is an application in various fields, including the food and beverage industry, packaging, and textile applications, to protect the environment from contamination and introduce a green demand for the near future. In this review, the chemical glycolysis process as an outstanding recycling technique for PET is also discussed, emphasizing the catalysts' performance, reaction conditions and methods, degradation agents, the kinetics of reactions, and reprocessing products. In general, a correct understanding of the PET recycling reaction mechanism leads to making the right decisions in waste management.

Dual-catalytic depolymerization of polyethylene terephthalate (PET)

Limiting our plastic waste and finding greener, more sustainable solutions for disposal is a current environmental priority.

Novel polyester diol obtained from PET waste and its application in the synthesis of polyurethane and carbon nanotube-based composites: swelling behavior and characteristic properties

Novel PUs and PU/CNTs were prepared from PET bottle waste and were characterized by a wide range of characterization methods.

Preparation and testing of a solid secondary plasticizer for PVC produced by chemical degradation of post-consumer PET

Post-consumer poly(ethylene therephthalate) (PET) obtained from milled water bottles was chemically degraded by glycolysis, using suitable amounts of diethylene glycol (DEG) and Ca/Zn stearate as catalyst system. The process was carried out by employing a melt mixer as the chemical reactor, which is the facility generally used for plastic compounding. The degraded PET products were first characterized from structural and thermal point of view by Fourier transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance ((1)H NMR), Size exclusion chromatography (SEC) Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA), and thereafter used alone or together with di(2-ethylhexyl) phthalate (DEHP) in poly(vinyl chloride) PVC formulations. The plasticization was, in fact, accomplished by using a binary system consisting of DEHP as primary plasticizer and a degraded PET product as secondary plasticizer (SP). The obtained materials were characterized through the main methods used to assess flexible PVC compounds: hardness in Shore A scale, thermal properties and quantitative migration of the plasticizer. The solid secondary plasticizer obtained from post-consumer PET improves both the processing characteristics and the thermal stability of the final flexible PVC compounds while maintaining their hardness within the top values of the Shore A scale. In addition, a considerable reduction of the plasticizers migration (23%) was obtained by optimizing the formulation.

Reactive Processing of Thermoplastic Polymers: A Review of the Fundamental Aspects

The review is devoted to the fundamental aspects of the reactive processing of thermoplastic polymers. First of all, some reactive processing examples, including polymer grafting (vinyl silane, maleic anhydride) and/or functionalization, bulk polymerization (urethane, lactams, acrylate, ∊-capolactone), polyester modification and new copolymers synthesis, are presented. From a fundamental point of view, the review covers the state of the art in the domains of rheology (specifically modelling of rheo-kinetics), diffusion and mixing in highly viscous reactive or non reactive media. Finally, 1, 2 and 3-D simulation of the reactive extrusion process in twin-screw extruder is reported at the end of the review.

Synthesis of amphiphilic poly(tetraethylene glycol succinate) and the thermosensitivity of its aggregation in water

Amphiphilic biodegradable polyester, poly(tetraethylene glycol succinate) (PTEGSuc), was synthesized via melt polycondensation of tetraethylene glycol and succinic acid on catalysis of p-toluenesulfonic acid. It was observed that PTEGSuc could self-assemble into micelles in water. In addition, thermosensitivity of PTEGSuc aggregation in water was first found in the experiment, and the critical aggregation temperatures could be controlled by solution concentration. Transmission electron microscopy was used to investigate the micellar morphologies of PTEGSuc in different solvents. It was found that particle shape is almost round although the micellar morphology is different depending on the solvent used. Based on the perfect properties, especially in micelle formation and thermosensitivity, PTEGSuc is promising in biomedical field as carrier of drug delivery system, scaffold of tissue engineering, and other medical devices.