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Recycling, Volume 4, Issue 4 (December 2019) – 6 articles

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Cover Story (view full-size image) A large body of evidence has shown that the linear economy model is unsustainable, considering the [...] Read more.
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Open AccessArticle
Protective Low-Density Polyethylene Residues from Prepreg for the Development of New Nanocomposites with Montmorillonite: Recycling and Characterization
Recycling 2019, 4(4), 45; https://doi.org/10.3390/recycling4040045 - 04 Dec 2019
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Abstract
A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the [...] Read more.
A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications. Full article
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Open AccessFeature PaperArticle
Design for Recycling in a Critical Raw Materials Perspective
Recycling 2019, 4(4), 44; https://doi.org/10.3390/recycling4040044 - 19 Nov 2019
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Abstract
The European Union (EU) identified a number of raw materials that are strategic for its economy but suffer at the same time from a high supply risk. Such critical raw materials (CRMs) are used in a wide range of commercial and governmental applications: [...] Read more.
The European Union (EU) identified a number of raw materials that are strategic for its economy but suffer at the same time from a high supply risk. Such critical raw materials (CRMs) are used in a wide range of commercial and governmental applications: green technology, telecommunications, space exploration, aerial imaging, aviation, medical devices, micro-electronics, transportation, defense, and other high-technology products and services. As a result, the industry, the environment, and our quality and modern way of life are reliant on the access and use of them. In this scenario, recycling may be a strategic mitigating action aimed at reducing the critical raw materials supply risks. In this work, a design strategy is proposed for alloys selection that minimizes the number of CRMs with the lowest end-of-life recycling input rate. The method is illustrated with an example. Full article
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Open AccessArticle
Contactless Resonant Cavity Dielectric Spectroscopic Studies of Recycled Office Papers
Recycling 2019, 4(4), 43; https://doi.org/10.3390/recycling4040043 - 05 Nov 2019
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Abstract
Current product composition and quality test methods for the paper and pulp industries are rooted in wet-bench chemistry techniques which cannot be used to distinguish between virgin and secondary fibers. We have recently demonstrated the application of an in situ and nondestructive assessment [...] Read more.
Current product composition and quality test methods for the paper and pulp industries are rooted in wet-bench chemistry techniques which cannot be used to distinguish between virgin and secondary fibers. We have recently demonstrated the application of an in situ and nondestructive assessment method based on dielectric spectroscopy (DS), which can address this deficiency in the testing of paper. The DS technique, which employs a resonant microwave cavity, could be applicable to quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC), and may have inherent forensic capabilities. In this paper, we show how this DS technique can be used to distinguish between office copier paper products which may contain recycled fibers. We show a reasonable correlation between the dielectric characteristics (e.g., dielectric loss) and the atomistic level chemical changes that result from the paper recycling process. Full article
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Open AccessArticle
Implementation of Circular Economy Principles in Industrial Solid Waste Management: Case Studies from a Developing Economy (Nigeria)
Recycling 2019, 4(4), 42; https://doi.org/10.3390/recycling4040042 - 21 Oct 2019
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Abstract
The existing solid waste management principles are increasingly being replaced with discussions on circular economy (CE) principles in contemporary deliberations on solid waste handling. This shift is supported by the global adoption of the concept of sustainable development. The CE offers better prospects [...] Read more.
The existing solid waste management principles are increasingly being replaced with discussions on circular economy (CE) principles in contemporary deliberations on solid waste handling. This shift is supported by the global adoption of the concept of sustainable development. The CE offers better prospects to solid waste management and has been implemented successfully in its full theory, practice, and policies in some developed locations of the world. The socio-economic disadvantages, insufficient expert knowledge and a lack of information have hindered its appropriateness and implementation in low and middle-income countries. Hence, the current research study examines the challenges and opportunities of implementing the circularity principle at the industrial sector level of a typical developing economy—Nigeria. Four different industries were selected for this case study—telecommunications, water packaging, pulp and paper and the food industry. These industries represent the major waste streams in an urban solid waste mix (waste electrical and electronic equipment (WEEE), plastic, paper and organic). This study discovered several barriers and existing pre-conditions in place that could either foster or militate against the smooth and successful application of a CE model as a simple modification of the generic model. This study also discussed future directions on the implementation of the model. Full article
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Open AccessArticle
Scenario Analysis on the Generation of End-of-Life Hybrid Vehicle in Developing Countries—Focusing on the Exported Secondhand Hybrid Vehicle from Japan to Mongolia
Recycling 2019, 4(4), 41; https://doi.org/10.3390/recycling4040041 - 15 Oct 2019
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Abstract
In recent years, Next-Generation Vehicles, especially Hybrid Vehicles (HV) are increasing rapidly in advanced countries. In fact, not only advanced countries but also some developing countries also own a large quantity of HV by importing secondhand HV from advanced countries. For instance, Mongolia [...] Read more.
In recent years, Next-Generation Vehicles, especially Hybrid Vehicles (HV) are increasing rapidly in advanced countries. In fact, not only advanced countries but also some developing countries also own a large quantity of HV by importing secondhand HV from advanced countries. For instance, Mongolia is importing a huge amount of secondhand HV from Japan every year. On the other hand, there will be a huge amount of waste HV in Mongolia that needs to be recycled properly soon, and yet, this problem has been neglected and the number of waste HVs in Mongolia is still unknown. The purpose of this research is to propose a method to predict the End-of-Life HV number in Mongolia. This research finds that the Japanese vehicle deregistration rate can represent vehicles’ durability and can be used to estimate End-of-Life HV number in Mongolia. The result shows that there will be a huge amount of End-of-Life HV as well as Nickel-Metal Hydride (NiMH) batteries generated in Mongolia from now on, even more than in Japan, which is the largest HV market. It is urgent for the Mongolian government to build a proper End-of-Life HV recycling system now, and international cooperation on resource circulation is also expected. Full article
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Open AccessArticle
Classification of Black Plastics Waste Using Fluorescence Imaging and Machine Learning
Recycling 2019, 4(4), 40; https://doi.org/10.3390/recycling4040040 - 10 Oct 2019
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Abstract
This work contributes to the recycling of technical black plastic particles, for example from the automotive or electronics industries. These plastics cannot yet be sorted with sufficient purity (up to 99.9%), which often makes economical recycling impossible. As a solution to this problem, [...] Read more.
This work contributes to the recycling of technical black plastic particles, for example from the automotive or electronics industries. These plastics cannot yet be sorted with sufficient purity (up to 99.9%), which often makes economical recycling impossible. As a solution to this problem, imaging fluorescence spectroscopy with additional illumination in the near infrared spectral range in combination with classification by machine learning or deep learning classification algorithms is here investigated. The algorithms used are linear discriminant analysis (LDA), k-nearest neighbour classification (kNN), support vector machines (SVM), ensemble models with decision trees (ENSEMBLE), and convolutional neural networks (CNNs). The CNNs in particular attempt to increase overall classification accuracy by taking into account the shape of the plastic particles. In addition, the automatic optimization of the hyperparameters of the classification algorithms by the random search algorithm was investigated. The aim was to increase the accuracy of the classification models. About 400 particles each of 14 plastics from 12 plastic classes were examined. An attempt was made to train an overall model for the classification of all 12 plastics. The CNNs achieved the highest overall classification accuracy with 93.5%. Another attempt was made to classify 41 mixtures of industrially relevant plastics with a maximum of three plastic classes per mixture. The same average classification accuracy of 99.0% was achieved for the ENSEMBLE, SVM, and CNN algorithms. The target overall classification accuracy of 99.9% was achieved for 18 of the 41 compounds. The results show that the method presented is a promising approach for sorting black technical plastic waste. Full article
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