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(a) Production of plastics worldwide from 1950 to 2018 (in million metric tons) and (b) PET plastic bottle recycling rates among different countries in 2017* and 2018
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This article is a short review of the circular material economy and recycling in the additive manufacturing (AM) of polymers. In the recent years, there has been a surge regarding the production of numerous products through AM of various polymers. AM can provide an opportunity for a better manufacturing solution to facilitate productivity and susta...
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Context 1
... the world is on the increase and in general is pernicious towards the environment causing pollution that harms aquatic species and humans. Polymer/plastic production has increased worldwide from 1.5 million metric tons in 1950 to 359 million metric tons in 2018 (Garside 2019). The production of plastics worldwide from 1950 to 2018 is shown in Fig. 2a. Approximately 4 to 12 million metric tons of plastics have accumulated in terrestrial waters, negatively affecting the aquatic life ( Jambeck et al. 2015). Due to their mass production and relatively low cost, polymers are increasingly used in day-to-day products for humans. Between 1950 and2015, 8300 million metric tons of plastics ...
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... is one method by which waste polymers have been remanufactured into new useful products. However, it is a complex process that involves a number of processing steps. Nevertheless, the life of polymers can be increased through recycling and reuse. The recycling of polymers has been substantially pursued by different nations. For instance, Fig. 2b shows the recycling rate of polyethylene terephthalate (PET)-based containers In the recent years, the processing of polymers through AM has increased due to the desirable characteristics of the process ( Ngo et al. 2018). AM, otherwise known as 3D printing, is a fast-growing technique that is making a revolution in the manufacturing ...
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CircularSeas European Project, as part of the European Union Circular Economy [1], aims at promoting the Green Economy by encouraging the development of green products, parts and components by Maritime Industries. The strategy is a combination of Circular Economy principles, with the use of ocean plastic waste for developing new greener materials,...
Citations
... As an alternative strategy and with the main objective of an increasingly sustainable society, the circular economy (CE) emerges [5]. This idea, highlighted within the European ecological transition process (European Green Pact, EC, 2019 [6]), is currently the subject of a large number of articles in the literature with the aim of finding alternative methods to the problem generated by the enormous impact that plastic waste generates [7][8][9]. ...
... Plan views of the different 3D printed specimens as a function of the printing speed(2,8,12,16, and 25 mm/s). The needle diameter was kept constant at 14 G for all studied conditions. ...
These authors contributed equally to this work. Abstract: The current high production of plastics has prompted the exploration of alternative pathways to facilitate recycling, aiming for a progressively sustainable society. This paper presents an alternative and affordable technology for treating waste expanded polystyrene (EPS) mixed with acetone in a 100:1 volume ratio to be used as 3D printing ink for Direct Ink Write technology. In order to optimize the printing parameters, a comprehensive study was conducted, evaluating different needle diameters, printing speeds, and bed temperature values to achieve homogenous pieces and a highly repeatable 3D printing process. Results showed that the main optimum printing parameters were using needles with diameters of 14 to 16 G and printing speeds ranging from 2 to 12 mm/s, which were found to yield the most uniform ribbons. Increasing the bed temperature, despite favoring acetone evaporation, led to the generation of more heterogeneous structures due to void growth inside the printed ribbons. Thus, employing room temperature for the bed proved to be the optimal value. Lastly, a comparative study between the starting material and the EPS after the printing process was conducted using FTIR-ATR and GPC analyses, ensuring the preservation of the original polymer's integrity during physical recycling.
... The concept of a circular economy (CE) in comparison with linear economy model. Developed based on[2]. ...
In recent years, plastics recycling has become one of the leading environmental and waste management issues. Along with the main advantage of plastics, which is undoubtedly their long life, the problem of managing their waste has arisen. Recycling is recognised as the preferred option for waste management, with the aim of reusing them to create new products using 3D printing. Additive manufacturing (AM) is an emerging and evolving rapid tooling technology. With 3D printing, it is possible to achieve lightweight structures with high dimensional accuracy and reduce manufacturing costs for non-standard geometries. Currently, 3D printing research is moving towards the production of materials not only of pure polymers but also their composites. Bioplastics, especially those that are biodegradable and compostable, have emerged as an alternative for human development. This article provides a brief overview of the possibilities of using thermoplastic waste materials through the application of 3D printing, creating innovative materials from recycled and naturally derived materials, i.e., biomass (natural reinforcing fibres) in 3D printing. The materials produced from them are ecological, widely available and cost-effective. Research activities related to the production of bio-based materials have gradually increased over the last two decades, with the aim of reducing environmental problems. This article summarises the efforts made by researchers to discover new innovative materials for 3D printing.
... There is an increased interest and publications exploring and developing additive circular ecosystems, such as [7], [11], [12]. The only published literature review that focuses specifically on the development of ISNs in the AM industry [13] considers a sample of 32 documents published until July 2020. ...
... Using the keywords co-occurrence network map, a cluster is highlighted comprising documents that focus on recycling within AM processes and technologies, with a particular focus on the use of plastics. Thus, corroborating the potential of the AM industry towards achieving sustainability ( [11], [16]. This is because the remanufacturing activity is still the main activity used by AM to promote the circular economy and industrial symbiosis, as reviewed in [13]. ...
Additive manufacturing is one of the most prominent technologies seen as an enabler for circular economy strategies, including the development of additive symbiotic networks. There is a gap in the literature regarding the understanding of how additive symbiotic networks can be developed, namely in identifying the wastes and by-products and additive manufacturing technologies that can be used to valorize these resources. This study aims to review the existing literature on the topics of industrial symbiosis and additive manufacturing. A sample of 83 documents was reached, with only 25 highlighting the potential for developing industrial symbiosis networks in the additive manufacturing context. Results show that the most used technologies to incorporate recycled materials included fused deposition modelling, fused filament fabrication and selective laser melting. Regarding waste or by-products exchanges, plastic polymers, biological wastes and metal powders are some of the most frequently exchanged materials. This makes evidence of the additive manufacturing industry’s potential to develop additive symbiotic networks in which wastes and by-products from other industries may be used as material inputs for additive manufacturing processes and technologies.KeywordsAdditive symbiotic networksBlockchain technologySupply chain structurecase study
... Assumptions about biocomposites include easy maintenance and recyclability at the end of life [13]. The disadvantages of biocomposites include lower heat resistance than traditional composites and the possibility that they are more sensitive to moisture [14]. ...
Wood-plastic composites (WPCs) represent composite materials that employ shredded wood combined with a thermoplastic substance, such as polylactic acid (PLA), to establish structural cohesion within the product profile. This amalgamation of materials results in a robust structure designed to fulfill specialized roles under the influence of pressure and temperature. Given the nature of the constituent materials, the resultant product can be classified as a biocomposite. The creation of such biocomposites entails a rigorous process necessitating the fine-tuning of specific parameters and suitable technologies. The foundational materials employed in this process must be both natural and biodegradable. However, it is noteworthy that natural components like fibers exhibit anisotropic behavior, wherein their mechanical attributes are contingent on the direction of the applied force. Consequently, predicting their performance during biocomposite production proves challenging. The principal objective of this study was to conduct a comparative analysis of wood-based composites incorporating PLA thermoplastic binding agents. The intention was to discern variations in density profiles arising from distinct measurement methodologies. Two measurement methods were used for the measurement: X-ray and spectrum desaturation. Additionally, the study sought to investigate the impact of introducing PLA additives at 25% and 50% concentrations on the fabrication of WPC from wood chips. The properties of these composites were assessed by considering the inherent traits of the composite materials.
... Circularity is an emerging field for the conversion of raw materials into green and sustainable products [1,2]. Innovation and new technological development have transformed open-loop manufacturing into closed-loop manufacturing [3,4]. ...
he circularity of polymer waste is an emerging field of research in Europe. In the present research, the thermal, surface, mechanical, and tribological properties of polypropylene (PP)-based composite produced by injection molding were studied. The pure PP matrix was reinforced with 10, 30, and 40% wt. of pure cotton, synthetic polyester, and polyethylene terephthalate post-consumer fibers using a combination of direct extrusion and injection molding techniques. Results indicate that PP-PCPESF-10% wt. exhibits the highest value of tensile strength (29 MPa). However, the values of tensile and flexural strain were lowered with an increase in fiber content due to the presence of micro-defects. Similarly, the values of modulus of elasticity, flexural modulus, flexural strength, and impact energy were enhanced due to an increase in the amount of fiber. The PP-PCCF-40% wt. shows the highest values of flexural constant (2780 MPa) and strength (57 MPa). Additionally, the increase in fiber loadings is directly proportional to the creation of micro-defects, surface roughness, abrasive wear, coefficient of friction, and erosive wear. The lowest average absolute arithmetic surface roughness value (Ra) of PP and PP-PCCF, 10% wt., were 0.19 µm and 0.28 µm. The lowest abrasive wear value of 3.09 × 10−6 mm3/Nm was found for pure PP. The erosive wear value (35 mm3/kg) of PP-PCCF 40% wt. composite material was 2 to 17 times higher than all other composite materials. Finally, the single-step analysis of variance predicts reasonable results in terms of the p-values of each composite material for commercial applications.
... Plastics are cost-effective, versatile materials that benefit society and improve people's quality of life in many ways. The global plastic production reached 367 million tonnes in 2020, an increase of >80% over the last 20 years [1,2]. The most commonly used polymer materials for many different applications are polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET). ...
Microplastics (MPs) are detected in the water, sediments, as well as biota, mainly as a consequence of the degradation of plastic products/waste under environmental conditions. Due to their potentially harmful effects on ecosystems and organisms, MPs are regarded as emerging pollutants. The highly problematic aspect of MPs is their interaction with organic and inorganic pollutants; MPs can act as vectors for their further transport in the environment. The objective of this study was to investigate the effects of ageing on the changes in physicochemical properties and size distribution of polyethylene terephthalate (PET), as well as to investigate the adsorption capacity of pristine and aged PET MPs, using pharmaceutical diclofenac (DCF) as a model organic pollutant. An ecotoxicity assessment of such samples was performed. Characterization of the PET samples (bottles and films) was carried out to detect the thermooxidative aging effects. The influence of the temperature and MP dosage on the extent of adsorption of DCF was elucidated by employing an empirical modeling approach using the response surface methodology (RSM). Aquatic toxicity was investigated by examining the green microalgae Pseudokirchneriella subcapitata. It was found that the thermooxidative ageing process resulted in mild surface changes in PET MPs, which were reflected in changes in hydrophobicity, the amount of amorphous phase, and the particle size distribution. The fractions of the particle size distribution in the range 100–500 μm for aged PET are higher due to the increase in amorphous phase. The proposed mechanisms of interactions between DCF and PET MPs are hydrophobic and π–π interactions as well as hydrogen bonding. RSM revealed that the adsorption favors low temperatures and low dosages of MP. The combination of MPs and DCF exhibited higher toxicity than the individual components.
... Polymeric waste has become a global concern as a result of increased microplastics accumulation in the environment [1]. Despite their numerous benefits, they cause serious environmental issues after their end of life [2,3]. According to the Organisation for Economic Co-operation and Development report 2022 [4], plastic waste generation has more than doubled over the last two decades, with only 9% of waste successfully recycled and the remaining ending up in landfills, incinerated, or leaking into the environment. ...
Fire retardants, although can impart fire-safety in polymeric composites, are detrimental to the mechanical properties. Biochar can be used, in conjunction with fire retardants, to create a balance between fire-safety and mechanical performance. It is possible to thermally dope fire retardants into the pores of biochar to make it functionalised. Thus, the current work is intended in identifying a composite having the combination of the most desirable fire retardant, bioplastic, and a suitable processing method. A comparison was made between two fire retardants (lanosol and ammonium polyphosphate), bioplastics (wheat gluten and polyamide 11), and composite processing methods (compression and injection moulding). It was found that wheat gluten containing ammonium polyphosphate-doped biochar made by compression moulding had the best fire-safety properties with the lowest peak heat release rate (186 kW/m2), the highest fire performance index (0.6 m2s/kW), and the lowest fire growth index (1.6 kW/ms) with acceptable mechanical properties compared to the corresponding neat bioplastic. Thus, for gluten-based polymers, the use of ammonium polyphosphate thermally doped into biochar processed by compression moulding is recommended to both simultaneously improve fire-safety and conserve the mechanical strength of the resulting biocomposites.
... According to the United States EPA (Environmental Protection Agency) definition of circular economy, "a circular economy reduces material use, redesigns materials, products, and services to be less resource intensive, and recaptures "waste" as a resource to manufacture new materials and products" 33 . Reuse and integration of recycled polymers in the fast-growing MEX -AM technology is anticipated to have tangible impacts on sustainable/green manufacturing and reinforce the circular economy paradigm 34 . ...
The continuous growth of annual production and consumption of polyethylene terephthalate (PET) is coined with increasing waste that leaks into the environment, landfills and oceans as microplastics and nano plastics fragments. Upcycling the recycled PET to make a feedstock for the fast-growing material-extrusion additive manufacturing (MEX-AM) technology can contribute to the solution and supports the concept of sustainable materials. In this work, extrudable filaments comprising recycled polyethylene terephthalate (rPET) with low-cost additives, such as a chain extender, toughening agent, reactive impact modifier, and non-reactive impact modifier, have been fabricated using the twin-screw extruder. The optimum extrusion process parameters for producing uniform filaments of different rPET compounded formulations have been identified. The compounded filaments are then printed into standard ASTM test specimens for thermal characterization and mechanical characterization, including glass transition and melting temperatures, crystallinity and crystallization temperature, tensile strength, tensile modulus, ductility, flexural strength, and Izod impact energy. Furthermore, the melt flow index for the filaments was measured. More significantly, the experimental data showed that compounding rPET with such additives in the reactive twin-screw extrusion process results in uniform filaments that display advantageous thermal and mechanical properties and can be used as a feedstock in the MEX-AM technology. This study suggests that compounding the recycled PET pellets with low-cost additives while extruding them into filaments for MEX-AM offers excellent potential to make high-value-added customized products from a sustainable polymer feedstock.
... To manage polymer wastes, FDM can be used. However, understanding the performance of recycled polymer products produced through AM is essential [84,86]. Figure 26 displays the procedure involved in converting plastic waste into filament subsequently processed as 3D printed products. ...
As a special review article, several significant and applied results in 3D printing and additive manufacturing (AM) science and technology are reviewed and studied. Which, the reviewed research works were published in 2020. Then, we would have another review article for 2021 and 2022. The main purpose is to collect new and applied research results as a useful package for researchers. Nowadays, AM is an extremely discussed topic and subject in scientific and industrial societies, as well as a new vision of the unknown modern world. Also, the future of AM materials is toward fundamental changes. Which, AM would be an ongoing new industrial revolution in the digital world. With parallel methods and similar technologies, considerable developments have been made in 4D in recent years. AM as a tool is related to the 4th industrial revolution. So, AM and 3D printing are moving towards the fifth industrial revolution. In addition, a study on AM is vital for generating the next developments, which are beneficial for human beings and life. Thus, this article presents the brief, updated, and applied methods and results published in 2020.Graphical Abstract
... The 40% HDPE/GME composite exhibits excellent adhesion during printing, and finite element analysis (FEA) of thermo-mechanical processes reveals a low distribution of thermal stress across different layers in the prints. This suggests that AM techniques offer improved strength compared to conventional methods in the manufacturing of metal composites [61,62]. ...
This review examines the mechanical performance of metal- and polymer-based composites fabricated using additive manufacturing (AM) techniques. Composite materials have significantly influenced various industries due to their exceptional reliability and effectiveness. As technology advances, new types of composite reinforcements, such as novel chemical-based and bio-based, and new fabrication techniques are utilized to develop high-performance composite materials. AM, a widely popular concept poised to shape the development of Industry 4.0, is also being utilized in the production of composite materials. Comparing AM-based manufacturing processes to traditional methods reveals significant variations in the performance of the resulting composites. The primary objective of this review is to offer a comprehensive understanding of metal- and polymer-based composites and their applications in diverse fields. Further on this review delves into the intricate details of metal- and polymer-based composites, shedding light on their mechanical performance and exploring the various industries and sectors where they find utility.
