Dynamic development of the automotive industry and the growing number of various vehicles generate demand for the global production of tires. Simultaneously, high performance of tires cause serious problems with further management and recycling of end-of-life tires. Therefore, searching for novel, environmentally-friendly and cost-effective rubber recycling methods is currently one of the biggest environmental challenges in the 21st century.

This work aims to report the recent progress in sustainable development of waste tires recycling technologies. A special attention was focused on current advances in waste tire rubber grinding technologies; ground tire rubber treatment methods and characteristics of ground tire rubber and reclaimed rubber.

Moreover, the main challenges affecting the future trends of the industrial application of waste tire rubber recycling technologies are also discussed.

A large amount of non-infected plastic wastes are being generated at the healthcare facilities all over the world. However, only a small fraction is recycled. Conventionally, the used plastics are either disposed in landfills or inadequately incinerated. These practices impart an adverse effect on our environment. Plastics are indispensable part of the medical sector owing to their high versatility. The outbreak of Covid-19 clearly showed the growing demand for single use plastics. Hence, completely avoiding plastics can be challenging at this point of time. Recycling of plastics is undoubtedly a solution to solve the crisis of plastic pollution. Medical plastic recycling is limited mainly due to difficulties involved in sorting or cleaning. Recycling medical plastic wastes is possible only through proper coordination between healthcare sector and recycling industries. New recycling technologies are to be adopted in a sustainable manner. Moreover, the plastics used in medical applications should be designed such that recycling is possible. This review highlights the downside of medical wastes and discusses the recycling potential of commonly used medical plastics.

Foaming of recycled poly(ethylene terephthalate) (rPET) was performed by supercritical carbon dioxide (sc-CO₂) assisted extrusion. The intrinsic viscosity (IV) of rPET was increased from 0.62 dl/g to 0.87 dl/g using an epoxy-functional chain extender, which provided adequate rheological properties for cell stabilization so that an apparent density of less than 0.15 g/cm³ became achievable. Homogeneous and talc induced heterogeneous crystal and cell nucleation, subsequent cell growth and stabilization processes were examined using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. It was found that using talc the crystallization temperature increases which results in smaller cell size distribution. A strong correlation was evinced between the apparent density and the Fourier transform near-infrared (NIR) spectrum of the foamed rPET samples enabling quick and non-destructive characterization. Accordingly, NIR spectroscopy is demonstrated as a suitable method for in-line quality monitoring during extrusion foaming of recycled PET, being especially prone to quality fluctuations.

Replacing conventional plastics with bioplastics, i.e., plastics that are bioderived and/or biodegradable, does not necessarily solve the issues of resource depletion and plastic waste accumulation. To come to a truly sustainable plastics economy, the growing bioplastics production must be paralleled with effective end-of-life strategies for bioplastics waste, which is essential for all bioplastics, regardless of their biodegradability. While there is no doubt on the importance to recycle biobased non-biodegradable bioplastics such as bio-polyethylene terephthalate (bioPET), bio-polyethylene (bioPE), and bio-polypropylene (bioPP), the scenario is not as clear for biodegradable bioplastics, for which biodegradation is often seen as the only acceptable end-of-life option. However, biodegradation is normally not aimed at recovering plastic materials or monomers to be reintroduced in the life cycle of plastic products, while this is specifically the aim of other types of recycling options, such as mechanical and chemical recycling, which address both waste management and primary resource preservation. Hence, since bioplastics production is growing and such materials will coexist with conventional plastics for decades to come, it is vital to find the best end-of-life pathways for each of the most common bioplastics.

Post-consumer plastic waste has reached levels that are dangerous for the environment and for human health, and its management now represents a big challenge. Plastic biodegradation and biorecycling emerges as an addition to the conventional plastic waste recycling methods. This review describes recent studies on enzyme-catalysed synthetic polymers biorecycling and biodegradation. The emphasize lies on the most successful cases as that of enzyme-catalysed depolymerisation of polyethylene terephthalate, using a specially engineered enzyme PET depolymerase, that has recently been developed into industrial technologies as well as on other recent promising discoveries of enzymes that are potentially capable of complete and controlled plastic degradation in mild conditions. The review also discusses polymer qualities that are causing diminished plastic biodegradation, and the protein engineering methods and tools to increase enzyme selectivity, activity and thermostability. Many fields of expertise have been used in the described studies, such as polymer chemistry, microbiology, mutagenesis, protein and process engineering. Applying this innovative interdisciplinary knowledge offers new perspectives for the environmental waste management and leads to a sustainable circular economy.

Since recycling of polymers is a preferred means of reducing unwanted wastes and land-filling activity, and recovering monomers or other materials of economic value, tertiary methods of recycling (chemical recycling) have been critically reviewed, giving special attention, in each case, to the chemical basis of the particular recycling pathway and its potential applicability. Recycling issues of each of the widely used commodity polymers - polyesters, polyamides, polyurethanes, epoxies, poly (vinyl chloride), polycarbonate, and polyolefins – have been discussed individually, giving attention to both conventional and unconventional methods of perceived high potential, such as enzymatic degradation, ionic liquids mediation, microwave irradiation, and treatment in super critical liquids as well as super fluids. In addition, novel emerging methods undergoing greater study at present, such as cross-alkane metathesis (CAM), tandem hydrogenolysis/aromatization, vitrimer-based recycling, and dynamic covalent bonding are also highlighted.

High-performance polymer materials with low dielectric constant and low dielectric loss have been widely used in high-speed communication network. This review briefly introduces several common polymer materials, including polyimides, poly(benzoxazole)s, poly(aryl ether)s, poly(tetrafluoroethylene), and various porous polymers. Moreover, the preparation technology, various properties and applications of common low-dielectric polymers are discussed. Based on the desired properties and requirements for applications as low dielectric materials, the possibility of further development of porous polymer materials is discussed.

With the ever-growing demand for 5G networks and the promise of real-time, mission-critical applications, the advanced antennas with high-bandwidth and highly reliable connectivity are urgently needed. 5G networks primarily operate in two areas of spectrum below 6 GHz (known as sub 6) and millimeter wave, which are much higher than the working frequency of 4G cellular networks, thus the previously used materials and integration techniques need to be updated accordingly. In this sense, liquid crystal polyesters (LCP) have been considered as ideal high performance microwave/millimeter wave (mm-wave) substrate and packing materials due to their outstanding properties. More specifically, the LCP normally exhibit good thermal stability, low water absorption, stable dielectric constant and loss tangent in millimeter wave frequency range, which leads to the increasing research interests of LCP for 5G devices application in both academia and industrial fields. However, the review articles focusing on the chemistry and materials aspects of LCP intended for 5G application are unexpectedly limited. In this article, we will summarize the research progress of LCP materials used in 5G networks in the view of polymer science and engineering. More specifically, the polymerization, chemical structure, aggregated state, properties, modification and processing of typical LCP are reviewed, which would be useful for promoting practical application of the LCP in key devices of 5G networks.

Recently, the demands for biodegradable and renewable materials for packaging applications have increased tremendously. This rise in demand is connected to the growing environmental concerns over the extensive use of synthetic and non-biodegradable polymeric packaging, polyethylene in particular. The performance of biodegradable polymers is discussed in this review, with a particular focus on the blends of starch and other polymers. Furthermore, in food packaging industry, microbial activities are of great concern. Therefore, incorporation of antimicrobial agents or polymers to produce barrier-enhanced or active packaging materials provides an attractive option for protecting food from microorganism development and spread. Additionally, the barrier, mechanical and other properties of biodegradable polymers are discussed. Lastly, the existing and potential applications for bioactive coatings on antimicrobial packaging materials are also addressed.

Bio-plastics have gained tremendous attention, due to the increasing environmental pressure on global warming and plastic pollution. Among them, poly (lactic acid) (PLA) is both bio-based and bio-degradable, which has been widely used in many disposable packaging applications. The global market for PLA demand doubles every 3-4 years, as estimated by Jem's law.

Compared to traditional petroleum-based plastics, PLA is more expensive and usually has less mechanical and physical properties. The recent compounding efforts and the commercialization of D(−) lactic acid and its polymer PDLA have the potential to improve the mechanical and thermal characteristics of PLA (e.g. by forming stereocomplex PLA) for applications in high-end markets. However, the usage of PLA in some other applications is still limited.

With a structure similar to PLA, poly (glycolic acid) (PGA) has promising characteristics such as good biodegradability and barrier properties, which is potentially a beneficial supplement to PLA. The modification of PLA with PGA can be achieved via co-polymerization, physical blending and multilayer lamination. PGA and its combination with PLA have been widely studied in bio-medical applications, but not been well developed at large scales due to its relatively high production cost. In this case, the development of novel production technology and the advent of government regulations are the key drivers for the global transition towards bioplastics. Recently, multiple governmental regulations have been released that restrict the use of traditional plastics and facilitate bio-degradable plastic applications. PGA can be derived from industrial waste gases using an innovative production technology, which reduces carbon emissions and its production cost. By developing the production and compounding technology, PGA can be combined with PLA to play an essential role for a sustainable and environmental friendly plastic industry, especially for single-used products requiring fast degradation at room temperature or in the nature environment.

This paper reviews the recent development of starch-based materials, including both fundamental and application researches. In order to overcome the weakness of pure starch-based materials, such as lower mechanical properties found in natural polymers and moisture sensitivity, various blends and composites have been developed in the last two decades. In practical, incorporation of any additives is sensitive in developing fully biodegradable starch-based materials. Furthermore, safety issues will be considered as priority regarding any additives for food packaging applications. Based on these concerns, various natural filler and edible reinforce agents, such as natural fibers, starch or cellulous crystals, and laver, have been used in starch-based materials. So-called self-reinforced techniques, reinforcing starch matrix by modified starch particles, have also been used in developing starch-based composites. During developing starch-based foams the unique function of water, acts as both plasticizer and blow agent for starch-based foam, has been systematically studied. So far, various conventional processing techniques such as extrusion, injection, compression molding, casting and foaming, as well as some new techniques such as reactive extrusion, have been adapted for processing starch-based polymeric materials. Various starch-based products have been developed and commercialized.

A significantly growing interest is to design new biodegradable polymers in order to solve fossil resources and environmental pollution problems associated with conventional plastics. A kind of new biodegradable polymers, aliphatic–aromatic co-polyesters have been researched widely and developed rapidly in recent years, since that can combine excellent biodegradability provided from aliphatic polyesters and good properties from aromatic polyesters. Out of which, poly (butylene-adipate-co-terephthalate) (PBAT) shows the most importance. PBAT has been commercialized by polycondensation reaction of butanediol (BDO), adipic acid (AA) and terephthalic acid (PTA) using general polyester manufacturing technology. And it has been considered to have desirable properties and competitive costs to be applied in many fields. Therefore, this review aims to present an overview on the synthesis, properties and applications of PBAT.

In this paper, identification system of plastic solid waste (PSW) based on near-infrared (NIR) reflectance spectroscopy in combination with Support Vector Machine (SVM) was presented. A device applied to obtain NIR spectra of plastics in the detection platform was developed. After pre-processing (normalized, 1st derivative and smooth), the repeatability of spectral absorption features was improved, which would assist the identification. A “principal component analysis (PCA)SVM” identification method was proposed to identify polypropylene (PP), polystyrene (PS), polyethylene (PE), poly(methyl methacrylate) (PMMA), acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate (PET) among plastics, and its identification accuracy can reach 97.5%. The type of samples could clearly be identified and the shape of samples could also be roughly discerned. It is clearly shown that this system can achieve good identification results while reducing costs considerably, which has great potential in industrial recycling.

Polyhydroxyalkanoates (PHA) have been produced by several bacteria as bioplastics in industrial scales. PHA commercialization has been challenging due to its complexity and the associated high cost together with instabilities on molecular weights (Mw) and structures, thus instability on thermo- and mechanical properties. PHA high production cost is related to complicated bioprocessing associated with sterilization, low conversion of carbon substrates to PHA products, and poor growth of microorganisms as well as complicated downstream separation. To reduce complexity of PHA production, robust microorganisms that are contamination resistant bacteria have been targeted especially extremophiles, developments of engineering approaches for extremophiles especially Halomonas spp. for better PHA production have been successfully conducted and termed as “next generation industrial biotechnology” (NGIB). Diverse PHA can also be produced by engineering Halomonas or Pseudomonas spp. This review introduces recent advances on engineering bacteria for enhanced PHA biosynthesis and diversity.

Fixation carbon dioxide into polymer is a feasible proposal to construct high value-added biodegradable plastic. These polymers are environmentally friendly and energy-saving owing to that the raw material is waste gas and finally they decompose back into CO₂. This review mainly focuses on our group work of recent advancements on CO₂-based copolymers, especially for poly (propylene carbonate) (PPC). We also extensively introduce the improvements on thermal and mechanical performances of PPC by physical and chemical modifications. Meanwhile, their practical application is further discussed in detail as well to replace the conventionally non-biodegradable plastics. The commercial PPC has already been found an enormous application prospect in versatile packaging industry.

The growing need of multifunctional materials with tailor made properties led in the last decades to the development of novel commercial polymer blends, possessing superior physical properties with respect to traditional matrices and showing economical advantages with respect to the synthesis of new plastics. Due to the progressive increase of the environmental concerns on the management of plastic wastes, the difficulties in the sorting technologies and the limited chemical compatibility between the greatest part of polymer pairs, the technical potential of polymer blends often remains unexploited when the recycling stage is considered. In some cases, also the addition of compatibilizers to recycled blends does not represent a satisfactory solution to retain and/or tailor their properties.

The aim of this review is that to perform a critical analysis of the potentialities of polymer blends recycling. After an introductive section on the problems and the definitions of plastics recycling, some basic concepts about the physical behaviour of polymer blends are reported. The third section of the review is focused on the analysis of the mechanical recycling of polymer blends, and a general distinction between recycling techniques applied to compatible and un-compatible polymer blends is performed. In this chapter, also the analysis of the recycling potential of commingled plastics deriving from unsorted wastes and of the effect of the thermal reprocessing on the morphological and thermo-mechanical behaviour of polymer blends is reported. Considering the increasing importance of bioplastics in the modern society, the fourth chapter of this review is focused on the mechanical and chemical recycling of blends containing bioplastics, with particular attention to polylactic acid (PLA) and thermoplastic starch (TPS) based blends. The key aspects of the recycling technologies applied to polymer blends and the future perspectives are summarized in the last section of the review.

It is well known that wind energy could represent a promising solution to the continuous increase of energy demand in the modern society. At the end of 2016 the European wind power amounted to 153.7 GW, distributed on 77,000 wind turbines and corresponding to the 10.4% of the electrical energy supplied. Considering the EU program to increase the renewable energy share to 27% by 2030, the key role of the wind energy in the next decade is clear. As the number of wind towers that will be dismantled in the next years will continuously increase, the development of sustainable practices to dispose of these plants at the end of their life is of utmost importance. Some parts of these turbines (tower, foundations, generator and gear box) are constituted by materials having elevated recycling rates, while the blades, that are nowadays made up of thermosetting fiber reinforced polymers, are very difficult to be recycled, because of the nature of the materials involved and their complex composition.

Therefore, the aim of this review is to present the state of the art in composite wind blades recycling. In the first chapter, some general concepts about wind energy and composite wind blades are presented. The second section of the work is devoted to the analysis of the most important methods for recycling composite laminates. In the third chapter, a presentation of the recycling processes directly applied on waste composite blades is reported. Considering the actual difficulties in composite blades recycling, particular attention is devoted in the fourth chapter to innovative solutions to develop composite structures with improved recyclability, with some examples of modified thermosetting composites, innovative thermoplastic laminates and composites reinforced with natural fibers. The key aspects of composite wind blades recycling and the future perspectives are summarized in the last section.

Polyurethane is a material that defines the word ‘versatile’. The structure property relationship of di-isocyanates and polyols is such that it provides ample variety and customization to the manufacturer. The properties of the polyurethane can range to extremes from soft touch coatings to rock hard rigid construction material. These mechanical, chtemical and biological properties and the ease of tailoring has produced a huge amount of interest in not only the scientific community but also in the concerned industries as well. The enhancement of the material can be done by manipulating the raw materials as well as adding different additives and nanomaterials as well. Proper modifications in the raw material can hence produce a polyurethane virtually suitable for every application. The study here throws light upon the basic chemistry of the building blocks of polyurethane and its recent advancements in applications in fields such as medical science, automobiles, coatings, adhesives, sealants, paints, textile, marine industry, wood composites and apparels.

For many years, 3D Printing technologies have created significant advancements in the fields of engineering and healthcare. 4D printing is also introduced, which is the advanced version of 3D printing. The process of 4D printing is when a printed 3D object becomes another structure due to the influence of outside energy inputs such as temperature, light, or other environmental stimuli. This technology uses the input of smart materials, which have the excellent capability of shape-changing. The self-assembly and programmable material technology aim to reimagine building, production, assembly of products, and performance. 4D printing is applied in various sectors such as engineering, medicine, and others. 4D printed proteins could be a great application. With this new dimension, 3D printed objects can change their shape by themselves over the influence of external stimuli, such as light, heat, electricity, magnetic field, etc. This paper discussed a brief about 4D printing technology. Various characteristics of 4D Printing for enhancing the manufacturing domain, its development, and applications are discussed diagrammatically. Conceptualised the Work Process Flow for 4D Additive Manufacturing and finally identified ten major roles of 4D printing in the manufacturing field. Although reversible 4D Printing itself is a fantastic development, it is innovative, and it employs durable and accurate reversal material during the shapeshift. It helps us create complicated structures that cannot be accomplished easily by traditional manufacturing technologies. It seems to be a game-changer in different industries by depending on natural factors instead of energy and changes the way to produce, develop, bundle, and ship goods entirely.

Additive manufacturing (AM) produces a complex shaped product from its data, layer by layer, with high precision and much less material wastage. As compared to the conventional manufacturing process, there are many positive environmental advantages of additive manufacturing technologies. Most importantly, there is less waste of raw material and the use of new and smart materials. It appears to concentrate on the output of a component on lesser material waste, energy usage, and machine emissions. There is a need to study the environmental sustainability of additive manufacturing technologies and their applications. As more businesses aim to strengthen their eco-footprint, sustainability in AM is gaining momentum. Visionary leaders of the industry are continually challenging their employees to find new ways to reduce waste, improving their workforce's manufacturing environment, and find innovative ways to use new materials to become more sustainable. The growth in value-added components, goods, and services has resulted from these initiatives. This paper discusses the significant benefit of additive manufacturing to create a sustainable production system. Finally, the paper identifies twelve major applications of AM for sustainability. Although additive manufacturing and technological dominance are being established with crucial industries, their sustainability advantages are visible in the current manufacturing scenario. The main goal is to identify the environmental benefits of additive manufacturing technologies over conventional manufacturing. Industries can now decide on suitable technologies to meet environmental goals.

Aqueous Polyurethane Dispersions (APUD) have been at the epicenter of the coating industry & research, devising greener solutions to modern coating problems. The formulation of APUDs involves many components namely, polyols, isocyanates, chain extenders, and ionic centers which enable the Polyurethane to be dispersed in water. This reduces the dependence on solvent-based coatings, providing a better and eco-friendly replacement for existing systems. Advantages like ambient temperature curing and excellent adhesion further reinforce the case for APUD. This review encompasses the synergistic effect of said components while painting a vivid picture of how they would affect the final properties of the coating.

The work was aimed at the investigation of influence of peroxide curing system on cross-linking and properties of rubber compounds based on SBR. First, the temperature of vulcanization and the amount of dicumyl peroxide on curing process and physical-mechanical properties were investigated. Then, co-agents Type I and Type II were added to the rubber formulations cured with peroxide. The results revealed that the increase in temperature leads to the acceleration of curing process while both, curing kinetics and physical-mechanical properties were influenced by the amount of peroxide. The application of Type I co-agents resulted in the acceleration of curing process and increase in cross-link density of vulcanizates, which was reflected in the increase of hardness and decrease of elongation at break. The influence of Type II co-agents on curing kinetics was negligible, while most of them caused the reduction in cross-linking degree of vulcanizates. Type I co-agents contributed to the improvement of tensile strength of vulcanizates, while the influence of Type II co-agents on tensile strength was of minor importance.