Recycling Of PET Research Articles

PET Recycling by Alcoholysis Using a New Heterogeneous Catalyst: Study and its Use in Polyurethane Adhesives Preparation

One of the most used plastics in the world is poly(ethylene terephthalate), PET, which is on the top of the list of recyclable polymers. In this work, it was studied the chemical recycling of PET by the alcoholysis reaction using diethylene glycol (DEG) and sodium metasilicate (NaMs) as catalyst. This catalyst was not used before for this kind of reaction and showed an activity as good as the most used compound (zinc acetate). The PET‐polyol was produced with the reaction conditions that showed the higher weight yield and the final product was used in polyurethane (PU) adhesives compositions. The PUs were obtained using PET‐polyol, tolylene diisocyanate (10, 20 or 30% NCOfree) and DEG as chain extender or glycerin (GLY) as crosslinker. The adhesives were poured into Pinus taeda wood and the speciments were taken into mechanical properties evaluation accordingly to ASTM D 2339‐98. The results indicated that the PU adhesives 10% NCOfree with DEG were able to support the highest shear stress force applied (7.5 Mpa).

Recycling of Waste Poly(ethylene terephthalate) Bottles by Alkaline Hydrolysis and Recovery of Pure Nanospindle-Shaped Terephthalic Acid.

Poly(ethylene terephthalate) (PET) is a versatile engineering plastic which exhibits exceptional mechanical and thermal properties. Huge amounts of PET are consumed in various industries such as food packaging industry, textile industry, in the manufacturing of audio, video tapes and X-ray films and so on. But due to its substantial fraction by volume in water bodies and its high persistence to the atmospheric and biological agents, it could be considered as a hazard substance. Thereby chemical recycling of PET serves as a solution to solid waste problem as it transforms PET into its monomers via hydrolysis. Chemical recycling of post consumed waste PET bottles via alkaline hydrolysis is the main aim of this paper. Operating parameters such as reaction time and temperature were optimized for the conversion of PET into nanospindle-shaped terephthalic acid (TPA). Depolymerization of PET was carried out via alkaline hydrolysis by varying reaction time and temperature and maximum yield of 92% was obtained at 200 °C with reaction time of 25 minutes. The formed TPA nanospindles were further characterized in detail which exhibited high crystallinity, purity and fascinating thermal and surface properties.

Enzyme-catalyzed simultaneous hydrolysis-glycolysis reactions reveals tunability on PET depolymerization products

PET depolymerization via enzymatic catalysis is one of the most promising technologies in the context of plastics circular economy. So far, hydrolysis reactions accounted for almost the totality of studies, since the glycolysis route was only recently reported. In the present work, a comparative analysis of hydrolysis and glycolysis of PET oligomers catalyzed by Humicola insolens cutinase (HiC) and Candida antarctica lipase B (CALB) showed completely distinct profiles of the reaction products and rates. Then, simultaneous hydrolysis-glycolysis reactions with varied water and ethylene glycol concentrations revealed a gradual increase of the esterified products mono(2-hydroxyethyl) terephthalate (MHET) and bis(2-hydroxyethyl) terephthalate (BHET) as the reaction medium became more organic. Erosion patterns on the PET surface during hydrolysis and glycolysis reactions were also shown to be different. The results here reported open new opportunities for the use of task-specific solvents for biotechnological PET recycling, providing versatility for the depolymerization products in different reuse technologies.

Chemical Recycling of Poly(ethylene terephthalate) (PET) by Alkaline Hydrolysis and Catalyzed Glycolysis

The poly(ethylene terephthalate) (PET) is a thermoplastic polyester, non-degradable in the environment with high resistance to chemical and physical agents. Due to the substantial amount of waste generated and accumulated in the environment, chemical recycling of post-consumer PET has been considered the most successful method for polymer recycling. This work presents results of chemical recycling of post-consumer PET via alkaline hydrolysis and glycolysis. The alkaline hydrolysis is considered the most suitable to the green chemistry and this method can be carried out using mild reaction conditions. The process results in a good yield (97%) to terephthalic acid (TPA). The catalyzed glycolysis of post-consumer PET was carried out in a short reaction time and relatively low temperature, with bis (2-hydroxyethyl) terephthalate (BHET) yield of 75%. TPA and BHET were characterized by FTIR and 1 H NMR techniques. The analyses proved to be successful in obtaining both products. Therefore, this work contributes to the chemical recycling studies of PET waste and encourages further studies along this research area. DOI: http://dx.doi.org/10.17807/orbital.v10i3.1104

Structural insight into molecular mechanism of poly(ethylene terephthalate) degradation

Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and thus are widely used in daily life. However, non-biodegradability, once thought to be an advantage offered by plastics, is causing major environmental problem. Recently, a PET-degrading bacterium, Ideonella sakaiensis, was identified and suggested for possible use in degradation and/or recycling of PET. However, the molecular mechanism of PET degradation is not known. Here we report the crystal structure of I. sakaiensis PETase (IsPETase) at 1.5 Å resolution. IsPETase has a Ser–His-Asp catalytic triad at its active site and contains an optimal substrate binding site to accommodate four monohydroxyethyl terephthalate (MHET) moieties of PET. Based on structural and site-directed mutagenesis experiments, the detailed process of PET degradation into MHET, terephthalic acid, and ethylene glycol is suggested. Moreover, other PETase candidates potentially having high PET-degrading activities are suggested based on phylogenetic tree analysis of 69 PETase-like proteins.

Depolymerization Study of PET Waste Using Aminoethylethanolamine and Recycled Product Application as Polyesteramide Synthesis

Recycling of poly(ethylene terephthalate) (PET) is a global concern due to generation of large volume of its post consumer waste and serious environmental problems caused as PET does not decompose in nature readily. Present research work aims at effective recycling of waste PET from soft drink bottles by aminolysis method and further utilization of the recycled product for high performance coating application. In the present study, we report aminoethylenethanolamine (AEEA) which till date is not studied much for chemical recycling of PET, having primary and secondary amine groups together with hydroxyl groups, for aminolysis reaction. The reaction parameters were optimized for conventional and microwave assisted technique by varying the ratio of raw materials, reaction time, temperature and power. The recycled oligomeric product was separated, purified and characterized for determination of amine value, hydroxyl value and by Fourier transform infrared spectroscopy, proton NMR (1H-NMR) spectroscopy. Further polyesteramides were successfully synthesized by partial replacement of neopentyl glycol by aminolyzed oligomeric product along with sebacic acid and phthalic anhydride. These resulting polyesteramides were further cured with commercial polyisocyanate curing agents and applied on mild steel panels. The cured coatings were evaluated for their optical, mechanical, chemical, thermal and anticorrosive properties. The partial replacement of recycled product of PET wastes exhibited comparative coating performance properties with respect to polyester polyol synthesized without any component based on recycled PET waste product.

A case for closed-loop recycling of post-consumer PET for automotive foams

Striving to utilize sustainable material sources, polyester polyols made via glycolysis and esterification of recycled polyethylene terephthalate (rPET) scrap were used to synthesize flexible polyurethane (PU) foams typically found in automotive interior applications. The objective of this endeavor was to ascertain if a closed-loop model could be established with the discarded PET feedstock. In five separate formulations, up to 50% of the total polyol content (traditionally derived from petroleum-based feedstock) was replaced with the afore-mentioned sustainable recycled polyols. These foams underwent mechanical, thermal, morphological, and physical characterization testing to determine feasibility for use in an automotive interior. Young’s modulus, tensile stress at maximum load, tear resistance, and compression modulus all increased by combined averages of 121%, 67%, 32%, and 150% over the control petroleum-based formulation, respectively, in foams possessing 50% rPET polyol content. Thermal stability also increased with sustainable polyol content; thermogravimetric analysis showed that 50% mass loss temperature increased by an average of 20 °C in foams containing 30% recycled polyol. Properties of density and SAG factor remained within 5% of the control petroleum-based reference foams. After comparing these findings to traditional polyols, a compelling argument can be made for the use of post-consumer automotive and industrial feedstocks in developing high-performing interior automotive PU foams.

Alkaline hydrolysis of PVC-coated PET fibers for simultaneous recycling of PET and PVC

Polyvinyl chloride (PVC)-coated poly(ethylene terephthalate) (PET) woven fibers are one of the hardest-to-recycle polymeric materials. Herein we investigate the possibility of recycling both PVC and PET through alkaline hydrolysis of PET. The coated woven fabrics were treated with NaOH, hydrolyzing the PET fibers into water-soluble sodium terephthalate, while the PVC could be removed by filtration. The PET fibers were completely hydrolyzed between 120 and 180 °C in the presence of 1 M NaOH solution, quantitatively yielding terephthalic acid. A minimum PVC dechlorination rate of 1% was simultaneously achieved at 120 °C. Furthermore, no alkaline hydrolysis of the plasticizer contained in the PVC, di(2-ethylhexyl)phthalate, was observed. Thus, the possibility of simultaneously recycling PET and PVC from PVC-coated woven fabrics was demonstrated. Kinetic analyses of PET hydrolysis and PVC dechlorination revealed that the simultaneously occurring reaction processes did not affect the progress of each other. Thus, the absence of interactions between PET, PVC, or their degradation products enables the design of a simplified recycling process without considering the interactions between the materials derived from coated woven fabrics.

Investigation into cross-contamination during cleaning efficiency testing in PET recycling

The cleaning efficiency of a PET recycling process is typically investigated by artificial contamination of post-consumer PET flakes within a so-called challenge test. Challenging of pilot plants or industrial scale lines is done be introducing a certain amount of contaminated flakes while running the process with non-contaminated flakes of different colour. After decontamination the contaminated flakes are separated from the non-contaminated flakes and only the contaminated flakes were analysed due to their residual contamination level. The European Food Safety Authority (EFSA), however, raised the question about cross-contamination, which might reduce the overall cleaning efficiency of the recycling process. Cross-contamination is defined as the transfer of surrogate contaminants from the initially contaminated to the initially not contaminated material during a challenge test. Data for the phenomenon of cross-contamination are not available in the scientific literature. Aim of the study was to close this gap by providing experimental data for cross-contamination by use of several challenge tests. As a result cross-contamination was found only at ratios of 1:1 between contaminated and non-contaminated PET flakes. At higher ratios which were typically applied in challenge tests on pilot plant or industrial scale line cross-contamination do not play a significant role. In addition, the results show that cross-contamination is negligible for volatile compounds.

Characterization of Terephthalic Acid Monomer Recycled from Post‐Consumer PET Polymer Bottles

SummaryThe idea of recycling of PET to obtain terephthalic acid (TPH) monomer is fast gaining traction; therefore it has become imperative to develop standard characterization methods to assess the purity of terephthalic acid using reliable and easily available laboratory equipment/techniques. Experimental studies on recycling of post‐consumer PET waste were conducted in a batch reactor. The PET was subjected to a de‐esterification reaction to break down the ester bonds via alkali decomposition in ethylene glycol at 155 °C under the influence of ultrasound. The end product, terephthalic acid, was characterized for the functional purity using UV‐Visible spectrophotometry, FT‐IR, and thermal methods. The terephthalic acid was ascertained by the characteristic peak at 240 nm using UV‐Visible spectrophotometer and was quantified using a commercially available standard sample of terephthalic acid. The purity of end product was confirmed using FT‐IR and thermogravimetric and differential thermal analysis.

Practical process for the chemical recycling of PET

Practical process for the chemical recycling of PET

Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods

Recycling of poly(ethylene terephthalate) (PET) is of crucial importance, since worldwide amounts of PETwaste increase rapidly due to its widespread applications. Hence, several methods have been developed, like energetic, material, thermo-mechanical and chemical recycling of PET. Most frequently, PET-waste is incinerated for energy recovery, used as additive in concrete composites or glycolysed to yield mixtures of monomers and undefined oligomers. While energetic and thermo-mechanical recycling entail downcycling of the material, chemical recycling requires considerable amounts of chemicals and demanding processing steps entailing toxic and ecological issues. This review provides a thorough survey of PET-recycling including energetic, material, thermo-mechanical and chemical methods. It focuses on chemical methods describing important reaction parameters and yields of obtained reaction products. While most methods yield monomers, only a few yield undefined low molecular weight oligomers for impaired applications (dispersants or plasticizers). Further, the present work presents an alternative chemical recycling method of PET in comparison to existing chemical methods.

Corrigendum

This Corrigendum is in reference to the manuscript “ Optimizing synthesis of PET oligomers end capped with phthalic/maleic anhydride via recycling of off grade PET using design of experiments” Journal of Thermoplastic Composite Materials, September 2014, 27: 1256–1277, DOI: 10.1177/0892705712470266, by Ali Reza Zahedi, Mehdi Rafizadeh, and Faramarz Afshar Taromi. On page 1256 the affiliation of Ali Reza Zahedi reads as: Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Islamic Republic of Iran. Authors forgot to write Dr Zahedi’s affiliation correctly. His affiliation is: School of New Technologies, Iran University of Science and Technology, Tehran, Iran

Sodium titanium tris(glycolate) as a catalyst for the chemical recycling of poly(ethylene terephthalate) via glycolysis and repolycondensation

Poly(ethylene terephthalate) (PET) was chemically recycled through glycolysis with ethylene glycol (EG) and repolycondensation of its main depolymerized product bis(2-hydroxyethyl terephthalate) (BHET). In this process, synthesized sodium titanium tris(glycolate) was used as a new catalyst for both reactions. The catalytic efficiency and selectivity of sodium titanium tris(glycolate) in both reactions has been investigated and compared with conventional catalysts used in glycolysis or polycondensation. The results indicate that sodium titanium tris(glycolate) is a desirable catalyst for chemical recycling of PET because it can present high catalytic activity and selectivity not only in glycolysis but also in repolycondensation, which means high cost of the catalysts separation between two reactions during chemical recycling process could be avoided. Meanwhile, a mechanism of the glycolysis of PET catalyzed by sodium titanium tris(glycolate) was proposed based on the results of interactions among BHET, EG and catalysts revealed by infrared spectroscopy.

Chemical Recycling of PET Wastes with Different Catalysts

Chemical recycling of polyethylene terephthalate, known as PET, has been the subject of increased interest as a valuable feedstock for different chemical processes. In this work, glycolysis of PET waste granules was carried out using excess ethylene glycol in the presence of different simple chemicals acting as catalysts, which are, namely, categorized in ionic liquids, metal salts, hydrotalcites, and enzymes. From every category, some materials as a sample were used, and the one which is going to bring the best result is noted. The effect of some parameters such as temperature, pressure, amount of sample, material ratio, and stirring rate was investigated. As a result we compared the best of each category with the others and final result is shown.

Microwave assisted glycolysis of poly(ethylene terephthalate) catalyzed by 1‐butyl‐3‐methylimidazolium bromide ionic liquid

ABSTRACTThe combination of ionic liquid (IL) associated with microwave energy may have some potential application in the chemical recycling of poly (ethylene terephthalate). In this processes, glycolysis of waste poly (ethylene terephthalate) recovered from bottled water containers were thermally depolymerized with solvent ethylene glycol (EG) in the presence of 1‐butyl‐3‐methyl imidazolium bromide ([bmim]Br) as catalyst (IL) under microwave condition. It was found that the glycolysis products consist of bis (2‐hydroxyethyl) terephthalate (BHET) monomer that separated from the catalyst IL in pure crystalline form. The conversion of PET reach up to 100% and the yield of BHET reached 64% (wt %). The optimum performance was achieved by the use of 1‐butyl‐3‐methyl imidazolium bromide as a catalyst, microwave irradiations temperature (170–175°C) and reaction time 1.75–2 h. The main glycolysis products were analyzed by 1H NMR, 13C NMR, LC‐MS, FTIR, DSC, and TGA. When compared to conventional heating methods, microwave irradiation during glycolysis of PET resulted in short reaction time and more control over the temperature. This has allowed substantial saving in energy and processing cost. In addition, a more efficient, environmental‐friendly, and economically feasible chemical recycling of waste PET was achieved in a significantly reduced reaction time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41666.

Recent Developments in the Chemical Recycling of Postconsumer Poly(ethylene terephthalate) Waste

Global production and consumption of poly(ethylene terephthalate) (PET) products has increased dramatically over the past few decades. World consumption of PET has exceeded 13 million tonnes, of which about 1.5 million tonnes is exclusively consumed by the packaging sector itself. However, this tremendous increase in PET consumption has resulted in the accumulation of an enormous quantity of waste, the disposal of which is complex day by day. Among different PET recycling methods, chemical recycling (chemolysis) is the most successful method to convert PET into its monomers/oligomers. This review presents in detail recent developments in the chemical recycling (glycolysis and aminolysis) of PET. The wide spectrum of depolymerizing agents used, the reaction conditions, catalysts, products of depolymerization, and their potential applications are described.

Polyesteramide resin from PET waste and fatty amide

Purpose – The purpose of this paper is synthesis of polyesteramide resin from jatropha oil and monomer from recycling of poly(ethylene terephthalate) (PET) to get the excellent benefit of individual structure. Along with the synthesis of polyesteramide resin, this research work will also help in recycling of PET waste and help for the conversion of monomer obtained from recycling of PET to value-added application. Design/methodology/approach – Polyesteramide resin was synthesized by conventional method, i.e. by converting jatropha oil to corresponding fatty amide, i.e. hydroxyl ethyl jatropha oil fatty acid amide (HEJA), and treating it with dicarboxylic acid, i.e. sebacic acid but bis(2-hydroxyethyl) terepthalamide (BHETA) is added, i.e. monomer of PET, and then resin synthesis is carried out. Synthesized resin is cured with isocyanate and used for coating application. Coating is characterized for physical, mechanical, thermal and anticorrosive properties. Findings – Coating shows excellent balance of flexibility and hardness due to structural difference in BHETA and HEJA. Aromatic structure of BHETA was helpful for increasing hardness and for retardation of degradation, and at the same time, aliphatic structure of HEJA was helpful for increasing flexibility of the coating. Amide linkage present in both help for better adhesion of coating to metal surface, which also helps to improve the mechanical properties and anticorrosive properties. Practical implications – This method is the practical solution for synthesis of polyesteramide resin and then coating from PET waste and jatropha oil. Hence the method developed is simple and it helps for recycling of PET waste and conversion of recycled product to value-added material. Originality/value – To the best of the authors’ knowledge, this is the first study which use jatropha oil (fatty amide of jatropha oil) and PET waste (monomer of PET waste) simultaneously for the synthesis of polyesteramide resin and then coating.

Poly (ethylene terephthalate) recycling for high value added textiles

AbstractThis study reviews the problems in the use and disposal of poly (ethylene terephthalate) (PET) and includes the concise background of virgin and recycled PET as well as their possible applications. The current state of knowledge with respect to PET recycling method is presented. Recycling of PET is the most desirable method for waste management, providing an opportunity for reductions in oil usage, carbon dioxide emissions and PET waste requiring disposal because of its non-degradability. Advanced technologies and systems for reducing contamination, mechanical and chemical recycling, and their applications are discussed, and the possibility of diverting the majority of PET waste from landfills or incineration to recycling is suggested.

Acrylonitrile–butadiene rubber functionalization for the toughening modification of recycled poly(ethylene terephthalate)

ABSTRACTThe incorporation of functionalized acrylonitrile–butadiene rubber (NBR) into recycled poly(ethylene terephthalate) (PET) was introduced as an effective route for modifying the properties of PET and as a new method for PET recycling as well. To achieve modified NBR, glycidyl methacrylate (GMA) was grafted onto NBR with optimized reactive mixing, in which the highest grafting degree and lowest gel content were generated. PET/NBR blends with and without GMA functionalization were produced by melt mixing, and the mechanical properties, dynamic mechanical thermal properties, and phase morphologies of the systems were determined and compared. We found that low amounts of peroxide initiator (dicumyl peroxide) and high levels of the GMA monomer in the presence of the styrene comonomer led to the maximum grafting degree and suppressed the competing rubber crosslinking and GMA homopolymerization reactions. The blend compatibility with PET determined from dynamic mechanical thermal analysis spectra and scanning electron microscopy images was greatly improved when the NBR‐grafted GMA was used instead of the neat NBR in the blend recipes. As a result, the rubber phase dispersed in the PET matrix more finely, and the impact strength of the blend advanced very significantly. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40483.