Prerequisites for successful recycling of polymer waste

An increasing awareness of ecological problems will enhance all activities towards recycling of polymers. In other words, we have to expect a fast increasing amount of recycled polymers. Today, most activities concentrate on the economical feasible part of recycling - waste of higher prized plastics, only slightly contaminated plastic waste. Public pressure and legislation request solutions for heavily contaminated commodity plastics from household waste as well. The strategy to produce thick walled, profiles out of comingled plastics will be a contribution towards, but not the solution of the problem. We have to make the serious attempt to separate specific polymers like PE, PS, PET from the waste and to introduce these recyclates into the plastic market. In other words, we have to establish closed loops for all our products. Tremendous problems lay ahead of us in order to accomplish it. We need markets for recyclate, we have to change specifications accordingly, we have to improve existing technologies for work up, we have to develop “raw material” specifications when we turn waste in an economic good, we have to develop scenarios for unsufficient economics. The paper will deal with all these aspects in detail and will discuss the present situation in Germany.     

Advances and approaches for chemical recycling of plastic waste

The global production and consumption of plastics has increased at an alarming rate over the last few decades. The accumulation of pervasive and persistent waste plastic has concomitantly increased in landfills and the environment. The societal, ecological, and economic problems of plastic waste/pollution demand immediate and decisive action. In 2015, only 9% of plastic waste was successfully recycled in the United States. The major current recycling processes focus on the mechanical recycling of plastic waste; however, even this process is limited by the sorting/pretreatment of plastic waste and degradation of plastics during the process. An alternative to mechanical processes is chemical recycling of plastic waste. Efficient chemical recycling would allow for the production of feedstocks for various uses including fuels and chemical feedstocks to replace petrochemicals. This review focuses on the most recent advances for the chemical recycling of three major polymers found in plastic waste: PET, PE, and PP. Commercial processes for recycling hydrolysable polymers like polyesters or polyamides, polyolefins, or mixed waste streams are also discussed.     

Recycling of polyethylene terephthalate (PET Or PETE) plastics – An alternative to obtain value added products: A review

Waste management is become one of the world's most pressing issues. Plastic is one of the most widely utilised materials in the modern world. Plastic manufacturing and usage have risen globally in recent decades due to its low weight and outstanding mechanical properties. Plastic has a wide range of applications due to such good properties include lightweight, high strength, and extended durability. Because of plastics are non- or low-biodegradable, a vast quantity of plastic waste is generated every day, making waste disposal the most pressing matter globally. Furthermore, improper waste disposal pollutes the environment. An ecologically friendly approach is necessary to locket these issues. One of the solutions is to recycle this sort of garbage. There are many plastic recycling technologies available, however practically all of them have certain restrictions. Chemical recycling of plastic, on the other hand, has been shown to be more efficient than other recycling methods. This article provides a quick overview of chemical recycling of PET post-consumer waste and the synthesis of potentially value-added products such as dye or dyestuffs, bolaform surfactant, bio-degradable polyesters, drug carrier, Metal-organic framework (MOF), bio-degradable polymeric scaffolds, polyurethane foam and coating materials etc.     

The Cradle-to-Cradle Life Cycle Assessment of Polyethylene terephthalate: Environmental Perspective

Over the last several years, the number of concepts and technologies enabling the production of environmentally friendly products (including materials, consumables, and services) has expanded. One of these ways is cradle-to-cradle (C2C) certified^TM. Life cycle assessment (LCA) technique is used to highlight the advantages of C2C and recycling as a method for reducing plastic pollution and fossil depletion by indicating the research limitations and gaps from an environmental perspective. Also, it estimates the resources requirements and focuses on sound products and processes. The C2C life cycle measurements for petroleum-based poly (ethylene terephthalate) (PET) bottles, with an emphasis on different end-of-life options for recycling, were taken for mainland China, in brief. It is considered that the product is manufactured through the extraction of crude oil into ethylene glycol and terephthalic acid. The CML analysis method was used in the LCIA for the selected midpoint impact categories. LCA of the product has shown a drastic aftermath in terms of environmental impacts and energy use. But the estimation of these consequences is always dependent on the system and boundary conditions that were evaluated throughout the study. The impacts that burden the environment are with the extraction of raw material, resin, and final product production. Minor influences occurred due to the waste recycling process. This suggests that waste degradation is the key process to reduce the environmental impacts of the production systems. Lowering a product’s environmental impact can be accomplished in a number of ways, including reducing the amount of materials used or choosing materials with a minimal environmental impact during manufacture processes.     

Biodegradability of conventional and bio-based plastics and natural fiber composites during composting,anaerobic digestion and long-term soil incubation

Plastics are a major constituent of municipal solid waste that pose a growing disposal and environmental pollution problem due to their recalcitrant nature. To reduce their environmental impacts and allow them to be transformed during organic waste recycling processes, various materials have recently been introduced to improve the biodegradability of plastics. These include conventional plastics amended with additives that are meant to enhance their biodegradability, bio-based plastics and natural fiber composites. In this study, the rate and extent of mineralization of a wide range of commercially available plastic alternative materials were determined during composting, anaerobic digestion and soil incubation. The biodegradability was assessed by measuring the amount of carbon mineralized from these materials during incubation under conditions that simulate these three environments and by examination of the materials by scanning electron micrography (SEM). The results showed that during a 660 day soil incubation, substantial mineralization was observed for polyhydroxyalkanoate plastics, starch-based plastics and for materials made from compost. However, only a polyhydroxyalkanoate-based plastic biodegraded at a rate similar to the positive control (cellulose). No significant degradation was observed for polyethylene or polypropylene plastics or the same plastics amended with commercial additives meant to confer biodegradability. During anaerobic digestion for 50 days, 20–25% of the bio-based materials but less than 2% of the additive containing plastics were converted to biogas (CH₄ + CO₂). After 115 days of composting, 0.6% of an additive amended polypropylene, 50% of a plastarch material and 12% of a soy wax permeated paper pulp was converted to carbon dioxide. SEM analysis showed substantial disintegration of polyhydroxyalkanoate-based plastic, some surface changes for other bio-based plastics and coconut coir materials but no evidence of degradation of polypropylene or polypropylene containing additives. Although certain bio-based plastics and natural fibers biodegraded to an appreciable extent in the three environments, only a polyhydroxyalkanoate-based resin biodegraded to significant extents during the time scale of composting and anaerobic digestion processes used for solid waste management.     

Quality assurance of recycled engineering plastics using blend technology

The automotive, electrical and electronic sectors account for over 12% of all plastics consumed. A large fraction of these polymers are engineering plastics representing a value considerably higher than that of commodity thermoplastics; hence, mechanical recycling including upgrading efforts appears economically attractive. This paper shows some methods of upgrading the property profile of ABS from dismantled automobiles using polymer blend technology. The results for blends of ABS with PC or PA are reported. The aim of blending of the waste materials is twofold: to reduce the number of plastic materials to be recycled in car dismantling plants, and to improve properties of the ABS scrap, which is the main engineering plastic in the waste stream from automobiles.     

Polymer and its effect on environment

This is an era where plastic pollution is increasing hazardously. Plastics are spreading all over the environment due to this it's a big threat to the equilibrium of the environment and health of the human beings. Its not due to their properties but it is also a strong carrier of pesticides, poly aromatic hydrocarbons, diphenyl, pharmaceutical products etc. Majorly plastics are being used everywhere like in packaging, water bottles etc. We have about to reach the stage where we require to produce biodegradable or recyclable plastic. It reduces the usage of oil, CO₂ emission and reduces the quantity of waste to be disposed. Phthalates, BPA and others should be banned in plastic products which are in direct contact with food, children and bio-degradable plastics should be more used. Our study focused on varieties of plastics, its hazardous impact on the environment especially on the environment, its recycling strategies and use of biodegradable materials.     

The stable hydrogen and oxygen isotope variation of water stored in polyethylene terephthalate (PET) bottles

A set of bottled waters from a single natural spring distributed worldwide in polyethylene terephthalate (PET) bottles has been used to examine the effects of storage in plastic polymer material on the isotopic composition (delta18O and delta2H values) of the water. All samples analyzed were subjected to the same packaging procedure but experienced different conditions of temperature and humidity during storage. Water sorption and the diffusive transfer of water and water vapor through the wall of the PET bottle may cause isotopic exchange between water within the bottle and water vapor in air near the PET-water interface. Changes of about +4 per thousand for delta2H and +0.7 per thousand for delta18O have been measured for water after 253 days of storage within the PET bottle. The results of this study clearly indicate the need to use glass bottles for storing water samples for isotopic studies. It is imperative to transfer PET-bottled natural waters to glass bottles for their use as calibration material or potential international working standards.     

A short review on latest developments in catalytic depolymerization of Poly (ethylene terephathalate) wastes

Chemical recycling of plastic wastes is top among the effective management of the solid wastes. Particularly the post-consumer polyethylene terephthalate (PET) plastic wastes mainly generated from the disposal of beverage bottles and placed third most produced polymeric waste. However, PET wastes could be chemically recycled using several types of homo-/heterogeneous acid or base catalysts, and an effective recycling process has yet to be achieved. Therefore, the present short review is intended to display recent reports on the depolymerization of PET polymer wastes. The review aimed to cover glycolysis and aminolytic depolymerization using various catalytic systems. There is a wide spectrum of catalytic systems such as metal oxides, ionic liquids, organic bases, nanoparticles, porous materials and microwave-assisted rapid depolymerization methods have been developed toward the yield enhancement of the depolymerized products. Ideologically, the present review would benefit the researchers in familiarizing themselves with the latest developments in this field.     

Atmospheric Plasma Sterilization and Deodorization of Dielectric Surfaces

A method is presented for rapid and uniform sterilization and deodorization of dielectric surfaces. The technology is applicable to the inside surface of PET or glass bottles, polymer caps, plastic tubes, etc. The treatment is based on a pulsed RF discharge in air at atmospheric pressure (eventually with addition of argon) creating a nonequilibrium plasma on the treated surface. The plasma effectively destroys microorganisms in vegetative or sporulent form. It also slightly etches the polymeric material, removing some atomic layers and, thereby, cleaning it from aromatic organic components (deodorization). The process is short: PET bottles 1.5 L, in particular, can be treated in about 20 msec. The results of surface analysis and microbiological, chromatography, and spectroscopy tests are discussed. A device has been developed and integrated into an industrial-filling machine for online sterilization and deodorization of the inside surface of PET bottles before filling, and for sterilization of caps and bottle necks before seaming. It allows cold asceptic filling at a rate of 36,000 bottles per hour.     

A New PETase from the Human Saliva Metagenome and Its Functional Modification via Genetic Code Expansion in Bacteria

The discovery and engineering of new plastic degrading enzymes is an important challenge in chemical biotechnology to enable transition to a more sustainable and circular plastics economy. This field has so far yielded a range of enzymes and microbial pathways for the recycling and valorization of plastic waste. New research from Uttamapinant et al. reports the discovery of a novel polyethylene terephthalate (PET) hydrolase from the human saliva metagenome that displays improved properties and catalytic performance over previously characterized PET hydrolases (PETases). The authors also demonstrate the site-specific incorporation of a photocaged unnatural amino acid, 2,3-diaminopropionic acid (DAP), which upon photodecaging enables covalent binding of DAP to the PET surface. Thus, this work highlights metagenomic datasets as an untapped source of new PET degrading enzymes and the chemical modification of PETases via genetic code expansion, enabling new biotechnologies for the circular plastics economy.     

Chemical Upcycling of Waste Plastics to High Value-Added Products via Pyrolysis: Current Trends,Future Perspectives,and Techno-Feasibility Analysis

Chemical upcycling of waste plastics into high-value-added products is one of the most effective, cost-efficient, and environmentally beneficial solutions. Many studies have been published over the past few years on the topic of recycling plastics into usable materials through a process called catalytic pyrolysis. There is a significant research gap that must be bridged in order to use catalytic pyrolysis of waste plastics to produce high-value products. This review focuses on the enhanced catalytic pyrolysis of waste plastics to produce jet fuel, diesel oil, lubricants, aromatic compounds, syngas, and other gases. Moreover, the reaction mechanism, a brief and critical comparison of different catalytic pyrolysis studies, as well as the techno-feasibility analysis of waste plastic pyrolysis and the proposed catalytic plastic pyrolysis setup for commercialization is also covered.     

Modelling of PET Quality Parameters for a Closed-Loop Recycling System for Food Contact

Summary: A rigorous process model has been developed which describes a closed-loop recycling system for PET beverage bottles. The reaction / mass transport model is aimed at the dominant quality parameters such as intrinsic viscosity, concentration of acetaldehyde, concentration of carboxylic end-groups, and concentration of vinyl end-groups, respectively. The model covers the main process steps being preform production (injection moulding), drying, solid-state polycondensation, and melt filtration. The simulation reveals that after a single recycling loop all the relevant quality parameters achieve the specification, if certain temperatures, residence times, and surface areas for degassing are provided during the recycling process. Another simulation showed the evolution of quality parameters in PET being subjected to an “infinite” number of recycling loops in a closed system. In this case, the concentration of acetaldehyde and vinyl end-groups decreases with the number of recycling loops, which is a desired effect. On the other hand, the concentration of carboxylic end-groups increases with every completed recycling loop. Higher concentrations of carboxylic end-groups make the polymer more susceptible to hydrolysis and increase the SSP process time needed to achieve the specified intrinsic viscosity for carbonated soft drink bottles. To overcome this problem, the recycled PET has to be blended with a certain amount of virgin PET in industrial processes.     

Optimization process for glycolysis of poly (ethylene terephthalate) using bio-degradable & recyclable heterogeneous catalyst

Because of characteristics including simplicity of processing, light weight, recyclability, and low cost of production, plastic production and usage have risen every day. As a result, there is now more waste plastic generated every day, and it will be opening up a brand-new field of study for researchers to investigate and solve these issues. An ecologically friendly approach is needed to solve these problems. One approach is to recycle this kind of waste. There are several ways to recycle used plastics, but practically all of them have good and bad points. About a few decades ago, the glycolysis of used PET polymers gained industrial attention. Since used poly (ethylene terephthalate) (PET) plastics may be recycled using the most advantageous and promising techniques. This works an optimization parameter of chemical recycling of PET waste without utilizing any solvent as a reaction medium by changing a number of variables, such as catalyst types and the molar ratio of EG: PET, catalyst ratio and also recycled catalyst and reagent. The recovered Bio-catalyst (OPA/BLA) still maintained excellent catalytic efficiency for PET Glycolysis after six consecutive cycles. Optimized reaction condition was PET:EG (1:16) molar ratio 1% w/w catalyst at 192–200 °C reaction temperature obtaining 60.32% Yield of BHET product at 98.40% of PET conversion. Final product was confirmed by FT-IR, ¹H NMR and GC-MS data.     

Dual Photo-Responsive Diphenylacetylene Enables PET In-Situ Upcycling with Reverse Enhanced UV-Resistance and Strength

A novel in situ chemical upcycling strategy for plastic waste is proposed by the customized diphenylacetylene monomer with dual photo-response. That is, diphenylacetylene reactive monomers are in situ inserted into the macromolecular chain of polyethylene terephthalate (PET) plastics/fibers through one-pot transesterification of slight-depolymerization and re-polymerization. On the one hand, the diphenylacetylene group absorbs short-wave high-energy UV rays and then releases long-wave low-energy harmless fluorescence. On the other hand, the UV-induced photo-crosslinking reaction among diphenylacetylene groups produces extended π-conjugated structure, resulting in a red-shift (due to decreased HOMO–LUMO separation) in the UV absorption band and locked crosslink points between PET chains. Therefore, with increasing UV exposure time, the upcycled PET plastics exhibit reverse enhanced UV resistance and mechanical strength (superior to original performance), instead of serious UV-photodegradation and damaged performance. This upcycling strategy at oligomer-scale not only provides a new idea for traditional plastic recycling, but also solves the common problem of gradual degradation of polymer performance during use.     

Recycling of polymeric composites

For material recycling, composites have to be separated into their components, as only non-mixed raw materials can grant high quality standards. A combined mechanical and subsequent electrostatic separation can be classified as highly economic because it is a dry treatment. This is demonstrated on wire scrap. The separated copper and synthetic materials are obtained in a high degree of purity. Chemical disaggregation of composites has been worked out with medicinal blister packs and beverage packs. Two methods of separation were used: separating the plastic-aluminium composite by dissolving the plastic material or dissolving the adhesive that bonds together the plastic and aluminium. To demonstrate the technical feasibility of the processes, a pilot plant with a capacity of up to 25 tons of blister pack material per year was built. Chemical separation with non-problematic aqueous media was demonstrated with flocked plastics. When integrating composites into chemical processes, questions concerning material specification as well as preparation and chemical utilization must be answered. Mechanical preparation of appropriate raw materials has been exemplified by mixed packing waste, carpet-floor waste, and synthetic material from electrical waste. After the raw materials were analyzed and studies of their quantity and compositions were made, their possible re-use as raw material within a chemical process has been elaborated.     

Effect of small amounts of poly(lactic acid) on the recycling of poly(ethylene terephthalate) bottles

Poly(ethylene terephthalate) (PET) is one of the most used commodity polymers, especially for food and beverage applications, and its recycling is of great importance because of the possible use in the textile and construction industries. On the other hand, the interest in biodegradable polymers has led, in recent years, to the use of materials such as poly(lactic acid) (PLA) also in the food and beverage industry. The presence of small amounts of PLA in the PET waste can significantly affect the post-consumer recycling process. In this work, the effect of the presence of small amounts of PLA on the recycling of PET bottles is investigated by rheological, mechanical, morphological and thermogravimetric analysis. The results indicate that this presence can significantly affect the rheological properties under non-isothermal elongational flow, while the mechanical properties were considerably affected only in some circumstances and the thermal stability was not significantly modified.     

Polymer cracking — New hydrocarbons from old plastics

The management of packaging waste is a significant issue covered by European Union legislation which sets demanding targets for the recycling of all materials, including plastics. Significant progress has been made by an industry consortium, led by BP Chemicals, in developing technology to help meet the recycling targets.     

Electrode materials derived from plastic wastes and other industrial wastes for supercapacitors

The present review not only devotes on the environmental consequences of plastic bag wastes and other industrial wastes observable in the landfills,in the oceans or elsewhere but also gives a new insight idea on conversion of them into worth material,carbon,for the best electrochemical supercapacitor.Transformation of plastic wastes into high-value materials is the incentive for plastic recycling,end-oflife handling case for plastic bag wastes in practice quite limited.The plastic recycling waste for reuse saves energy compared with manufacturing virgin materials.Herein,we identified several synthetic methods to convert plastic waste and other industrial wastes into carbon material for supercapacitor.Different kinds of carbon materials,including nanofiber,nanotube,graphene,mesoporous carbon,etc.,have been derived from plastic waste,and thus give a superior potential for transforming trash into a "gold capacitor".Finally,conclusions and future trends of high-voltage supercapacitors were made as well as the easy and mass production of high-performance electrode materials for supercapacitors.Our work offers a promising sustainable approach to handle plastic bags,waste,and other industrial wastes and provides a new avenue in supercapacitor applications and other areas.     

A new approach to obtain Kevlar-49 from PET waste bottles

Non-biodegradable polyethylene terephthalate (PET) bottles have attracted increasing attention due to environmental concern in today’s world. In order to reduce the amount of solid wastes generated and the dependency on fossil resources, a new approach has been conducted to prepare Kevlar-49 from PET waste bottles. Terephthalic acid, the main raw material used for preparation of Kevlar, was regenerated from PET waste bottles via subjection to a saponification process, whereas p-phenylenediamine was prepared from PET waste bottles via the Hoffmann rearrangement method. Kevlar was synthesized from the reaction of terephthalic acid and p-phenylenediamine by polycondensation reaction. The structures of terephthalic acid, p-phenylenediamine and Kevlar were characterized by FT-IR, ¹H NMR, ¹³C NMR, and elemental analysis (CHN). In this study, thermogravimetric analysis and differential scanning calorimetry, X-ray diffraction (XRD), as well as the mechanical properties (tensile strength, modulus, and percentage elongation at break) of the synthesized Kevlar-49, were compared with commercial Kevlar-49, prepared from the same raw materials, for better understanding of their properties.