Polymers

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28 pages, 15943 KiB

Open AccessArticle

Evaluation of Improvements in the Separation of Monolayer and Multilayer Films via Measurements in Transflection and Application of Machine Learning Approaches

by Gerald Koinig, Nikolai Kuhn, Chiara Barretta, Karl Friedrich and Daniel Vollprecht

Polymers 2022, 14(19), 3926; https://doi.org/10.3390/polym14193926 - 20 Sep 2022

Cited by 8 | Viewed by 2123

Abstract

Small plastic packaging films make up a quarter of all packaging waste generated annually in Austria. As many plastic packaging films are multilayered to give barrier properties and strength, this fraction is considered hardly recyclable and recovered thermally. Besides, they can not be [...] Read more.

Small plastic packaging films make up a quarter of all packaging waste generated annually in Austria. As many plastic packaging films are multilayered to give barrier properties and strength, this fraction is considered hardly recyclable and recovered thermally. Besides, they can not be separated from recyclable monolayer films using near-infrared spectroscopy in material recovery facilities. In this paper, an experimental sensor-based sorting setup is used to demonstrate the effect of adapting a near-infrared sorting rig to enable measurement in transflection. This adaptation effectively circumvents problems caused by low material thickness and improves the sorting success when separating monolayer and multilayer film materials. Additionally, machine learning approaches are discussed to separate monolayer and multilayer materials without requiring the near-infrared sorter to explicitly learn the material fingerprint of each possible combination of layered materials. Last, a fast Fourier transform is shown to reduce destructive interference overlaying the spectral information. Through this, it is possible to automatically find the Fourier component at which to place the filter to regain the most spectral information possible. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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13 pages, 1968 KiB

Open AccessArticle

One-Pot Reactive Melt Recycling of PLA Post-Consumer Waste for the Production of Block Copolymer Nanocomposites of High Strength and Ductility

by Kalyanee Sirisinha, Supa Wirasate, Chakrit Sirisinha and Noppasorn Wattanakrai

Polymers 2022, 14(17), 3642; https://doi.org/10.3390/polym14173642 - 2 Sep 2022

Cited by 5 | Viewed by 1905

Abstract

Post-consumer waste recycling is a crucial issue for building a sustainable society. However, mechanical recycling of poly(lactic acid) (PLA) often reduces the performance of the recycled material because PLA has a strong tendency to degrade during reprocessing. Therefore, it is of great interest [...] Read more.

Post-consumer waste recycling is a crucial issue for building a sustainable society. However, mechanical recycling of poly(lactic acid) (PLA) often reduces the performance of the recycled material because PLA has a strong tendency to degrade during reprocessing. Therefore, it is of great interest to develop an effective recycling method to improve the mechanical performance of this material. This paper presents a one-pot melt process for turning PLA waste into a biodegradable block copolymer and its high strength and ductility composite. The process was conducted in a melt-mixer through a transesterification of PLA with poly(ethylene glycol) (PEG) or poly(propylene glycol) (PPG) as a soft component and clay as reinforcement. Effects of soft component content and sequence of clay addition on the mechanical performance of the prepared materials were focused. The results showed the successful preparation of PLA-based multiblock copolymers of high molecular weights (~100 kDa). Both virgin PLA and recycled source could serve as the starting material. PEG was more efficient than PPG in providing an intense improvement of PLA ductility. The nanocomposite of intercalated structure yielded nearly 100 times higher elongation at break (E_b = 506%) than the starting PLA (E_b = 5.6%) with high strength of 39.5 MPa and modulus of 1.4 GPa, considering the advantages of clay addition. Furthermore, the products with a broadened range of properties can be designed based on the ratio of PLA and soft component, as well as the organization and spatial distribution of clay in the copolymer matrices. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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35 pages, 20566 KiB

Open AccessArticle

Lifecycle Assessment for Recycling Processes of Monolayer and Multilayer Films: A Comparison

by Gerald Koinig, Elias Grath, Chiara Barretta, Karl Friedrich, Daniel Vollprecht and Gernot Oreski

Polymers 2022, 14(17), 3620; https://doi.org/10.3390/polym14173620 - 1 Sep 2022

Cited by 6 | Viewed by 2844

Abstract

This work covers a lifecycle assessment of monolayer and multilayer films to quantify the environmental impacts of changing the management of plastic film waste. This lifecycle assessment offers the possibility of quantifying the environmental impacts of processes along the lifecycle of monolayer and [...] Read more.

This work covers a lifecycle assessment of monolayer and multilayer films to quantify the environmental impacts of changing the management of plastic film waste. This lifecycle assessment offers the possibility of quantifying the environmental impacts of processes along the lifecycle of monolayer and multilayer films and mapping deviating impacts due to changed process parameters. Based on the status quo, the changes in global warming potential and abiotic fossil resource depletion were calculated in different scenarios. The changes included collecting, sorting, and recycling mono- and multilayer films. The “Functional Unit” under consideration comprised 1000 kg of plastic film waste, generated as post-consumer waste in Austria and captured in the lightweight packaging collection system. The results showed the reduction of environmental impacts over product lifecycles by improving waste management and creating a circular economy. Recycling all plastic film reduced global warming potential by 90% and abiotic fossil resource consumption by 93%. The necessary optimisation steps to meet the politically required recycling rates by 2025 and 2030 could be estimated, and the caused environmental impacts are presented. This work shows the need for increased collection, recycling, and significant improvement in the sorting of films to minimise global warming potential and resource consumption. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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18 pages, 6932 KiB

Open AccessArticle

The Influence of Low-Energy Impact Loads on the Properties of the Sandwich Composite with a Foam Core

by Andrzej Komorek, Paweł Przybyłek, Robert Szczepaniak, Jan Godzimirski, Marek Rośkowicz and Szymon Imiłowski

Polymers 2022, 14(8), 1566; https://doi.org/10.3390/polym14081566 - 12 Apr 2022

Cited by 12 | Viewed by 2534

Abstract

Composite materials are widely used in the construction of means of transport. Due to their low density and high stiffness, sandwich composites generate significant interest. The authors conducted static and dynamic tests in order to determine the effect of density and core thickness [...] Read more.

Composite materials are widely used in the construction of means of transport. Due to their low density and high stiffness, sandwich composites generate significant interest. The authors conducted static and dynamic tests in order to determine the effect of density and core thickness on the mechanical properties of a sandwich composite. Particular attention was paid to the impact properties of such composites. Herex and Airex polymer foams of different densities were used as cores, whereas the faces were made up of two layers of fabrics: glass and carbon. The matrix base of the tested materials was made of epoxy resin cured with a dedicated hardener. As a result of the study, a significant influence of the core on the strength parameters of the tested spacer materials was found. The examined polymer foams were found to have different adhesive properties, which affected their residual strength after an impact and the nature of destruction of the studied composites. It was observed that sandwich composites with a thicker core of higher density have higher impact strength and resistance to puncture. In the sandwich composites, low-energy impact loads result in damage only to the layer to which the load has been applied and has a core, so repairing such an element is much easier than in classic layered composites without a core. What is very important is that, in contrast to classic laminates, the bottom cover of the composite is not destroyed at low-impact energy values. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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13 pages, 3094 KiB

Open AccessArticle

Towards Sustainable Composite Manufacturing with Recycled Carbon Fiber Reinforced Thermoplastic Composites

by Sarianna Palola, Pekka Laurikainen, Sonia García-Arrieta, Egoitz Goikuria Astorkia and Essi Sarlin

Polymers 2022, 14(6), 1098; https://doi.org/10.3390/polym14061098 - 9 Mar 2022

Cited by 11 | Viewed by 6860

Abstract

Currently, the vast majority of composite waste is either landfilled or incinerated, causing a massive burden on the environment and resulting in the loss of potentially valuable raw material. Here, conventional pyrolysis and reactive pyrolysis were used to reclaim carbon fibers from aeronautical [...] Read more.

Currently, the vast majority of composite waste is either landfilled or incinerated, causing a massive burden on the environment and resulting in the loss of potentially valuable raw material. Here, conventional pyrolysis and reactive pyrolysis were used to reclaim carbon fibers from aeronautical scrap material, and to evaluate the feasibility of using reclaimed carbon fibers in structural components for the automotive sector. The need for fiber sizing was investigated as well as the behavior of the fiber material in macroscopic impact testing. The fibers were characterized with the single fiber tensile test, scanning electron microscopy, and the microbond test. Critical fiber length was estimated in both polypropylene and polyamide matrices. Tensile strength of the fiber material was better preserved with the reactive pyrolysis compared to the conventional pyrolysis, but in both cases the interfacial shear strength was retained or even improved. The impact testing revealed that the components made of these fibers fulfilled all required deformation limits set for the components with virgin fibers. These results indicate that recycled carbon fibers can be a viable option even in structural components, resulting in lower production costs and greener composites. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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17 pages, 4017 KiB

Open AccessArticle

Intelligent Predicting of Product Quality of Injection Molding Recycled Materials Based on Tie-Bar Elongation

by Hanjui Chang, Zhiming Su, Shuzhou Lu and Guangyi Zhang

Polymers 2022, 14(4), 679; https://doi.org/10.3390/polym14040679 - 10 Feb 2022

Cited by 11 | Viewed by 3210

Abstract

In the process of injection molding, a certain percentage of recycled material is usually used in order to save costs. The material properties of recycled materials can change significantly compared with raw materials, and the quality of their molded products is more difficult [...] Read more.

In the process of injection molding, a certain percentage of recycled material is usually used in order to save costs. The material properties of recycled materials can change significantly compared with raw materials, and the quality of their molded products is more difficult to control. Therefore, it is crucial to propose a method that can effectively maintain the yield of the recycled material products. In addition, the variation of clamping force during the injection molding process can be determined by measuring the tie-bar elongation of the injection molding machine. Therefore, this study proposes a real-time product quality monitoring system based on the variation of clamping force during the injection molding process for the injection molding of recycled materials for plastic bottle caps. The variation of clamping force reflects the variation of cavity pressure during the injection molding process and further maps the variation of injection parameters during the injection molding process. Therefore, this study evaluates the reliability of the proposed method for three different injection parameters (residual position, metering end point and metering time). Experiments have shown that there is a strong correlation between the quality (geometric properties) and weight of the product under different molding parameters. Moreover, the three main injection parameters have a strong influence on the weight and quality of the plastic caps. The variation of the clamping force is also highly correlated with the weight of the plastic bottle cap. This demonstrates the feasibility of applying the variation of clamping force to monitor the quality of injection molded products. Furthermore, by integrating the clamping force variation index with the calibration model of the corresponding injection parameters, it is possible to control the weight of the plastic cap within the acceptable range of the product in successive production runs. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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Review

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18 pages, 7042 KiB

Open AccessReview

A Review of Composite Phase Change Materials Based on Biomass Materials

by Qiang Zhang, Jing Liu, Jian Zhang, Lin Lin and Junyou Shi

Polymers 2022, 14(19), 4089; https://doi.org/10.3390/polym14194089 - 29 Sep 2022

Cited by 26 | Viewed by 4323

Abstract

Phase change materials (PCMs) can store/release heat from/to the external environment through their own phase change, which can reduce the imbalance between energy supply and demand and improve the effective utilization of energy. Biomass materials are abundant in reserves, from a wide range [...] Read more.

Phase change materials (PCMs) can store/release heat from/to the external environment through their own phase change, which can reduce the imbalance between energy supply and demand and improve the effective utilization of energy. Biomass materials are abundant in reserves, from a wide range of sources, and most of them have a natural pore structure, which is a good carrier of phase change materials. Biomass-based composite phase change materials and their derived ones are superior to traditional phase change materials due to their ability to overcome the leakage of phase change materials during solid–liquid change. This paper reviews the basic properties, phase change characteristics, and binding methods of several phase change materials (polyethylene glycols, paraffins, and fatty acids) that are commonly compounded with biomass materials. On this basis, it summarizes the preparation methods of biomass-based composite phase change materials, including porous adsorption, microencapsulation based on biomass shell, and grafting by copolymerization and also analyzes the characteristics of each method. Finally, the paper introduces the latest research progress of multifunctional biomass-based composite phase change materials capable of energy storage and outlines the challenges and future research and development priorities in this field. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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26 pages, 1716 KiB

Open AccessReview

Searching Nanoplastics: From Sampling to Sample Processing

by Marina Cerasa, Simona Teodori and Loris Pietrelli

Polymers 2021, 13(21), 3658; https://doi.org/10.3390/polym13213658 - 23 Oct 2021

Cited by 29 | Viewed by 4725

Abstract

Nanoplastics (NPs) are considered emerging pollutants, namely unregulated contaminants whose toxic effect on humans and the environment has been demonstrated or suspected. They are the result of the physical fragmentation of the plastics that over time reach smaller dimensions (<100 nm). The issues [...] Read more.

Nanoplastics (NPs) are considered emerging pollutants, namely unregulated contaminants whose toxic effect on humans and the environment has been demonstrated or suspected. They are the result of the physical fragmentation of the plastics that over time reach smaller dimensions (<100 nm). The issues related to the characterization and quantification of NPs in the environmental matrices are mainly related to the infinitepsimal size, to the fact that they are found in bulk, and to the different physico-chemical forms in which the same polymer can evolve over time by degradation. To deal with the study of a new class of pollutants it is necessary to assess the entire analytical method, carefully considering every single step (sampling, cleanup, qualitative, and quantitative analysis) starting from the validation method in the laboratory. This paper reviews the analytical method steps, focusing on the first ones, which the current literature often underestimates: laboratory tests, sampling, and sample processing; in fact, most errors and the quality of the analyses often depend on them. In addition, all newly introduced sample processing methods were examined. Full article

(This article belongs to the Special Issue Advances in Sustainable Plastics and Polymer Composites)

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