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Recycled Polymer Composites: Futuristic Sustainable Material

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A special issue of Journal of Composites Science (ISSN 2504-477X). This special issue belongs to the section "Polymer Composites".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 17163

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Dr. Abhishek Kumar Pathak

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Guest Editor

Department of Aeronautics and Astronautics, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
Interests: CFRP; nanocomposites; shape-memory polymer; nanomaterials; mechanical and thermal properties; chemical synthesis

Special Issue Information

Dear Colleagues,

Higher dependency on plastic material due to lightweight and low cost makes it the most used human-made materials other than metals and cement. Unlike other natural materials, the decomposition of plastic material is one of the biggest concerns. Plastic materials such as polypropylene (PP), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyurethane (PU), and polystyrene (PS) are widely used thermoplastic in the automobile and aerospace industry and contribute a significant part in total plastic waste. Reusability of plastic material without compromising its mechanical and thermal performance is an essential step towards sustainable polymer composite material development.

A significant disadvantage of recycled plastic is brittleness, low impact resistance, and toughness after reheating, melt, and remolding. The internal structure of recycled plastic significantly changed throughout the production process, reflected in the form of heterogeneity and anisotropies to the mechanical properties, limiting the application of recycled polymer composites for various lightweight applications.

Typical processes involving improving or maintaining the mechanical properties of recycled plastic are advanced recycling process, polymer blending, and the addition of nanofillers such as nanofibers, graphene and carbon nanotubes, etc., in the recycled polymer. All the above processes can be achieved by injection and compression molding processes as well as extrusion.

The main aim of this Special Issue is to collect various investigations focused on the processing and recovery of original plastic properties by adding additional polymer and nanomaterials. Papers presenting studies on the effective blending and nanomaterial on the mechanical properties of the recycled composite products and materials are welcome in the Special Issue. Researchers who use a particular agent such as compatibilizer, toughening agents to improve composites' performance are welcomed to submit papers. Authors are encouraged to present new ideas, reusability, and applications to provide a complete framework on these groundbreaking materials and facilitate their use in different structural applications.

Dr. Abhishek Kumar Pathak
Guest Editor

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Keywords

Thermoplastic
Recycling
Nanocomposites
Nanomaterials
Molding
Extrusion
Mechanical and thermal properties
Morphological study
Chemical characterization
Dispersion
Blending

Published Papers (10 papers)

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Research

13 pages, 4554 KiB

Open AccessArticle

Polypropylene Composites Reinforced with Lignocellulose Nanocrystals of Corncob: Thermal and Mechanical Properties

by Edgar Mauricio Santos-Ventura, Marcos Alfredo Escalante-Álvarez, Rubén González-Nuñez, Marianelly Esquivel-Alfaro and Belkis Sulbarán-Rangel

J. Compos. Sci. 2024, 8(4), 125; https://doi.org/10.3390/jcs8040125 - 29 Mar 2024

Viewed by 480

Abstract

Composites based on recycled polypropylene (PP) reinforced with cellulose nanocrystals whit lignin corncob were prepared. The effect of the ratio composites prepared via a compression molding process on the mechanical and thermal properties was analyzed. Corncobs is a little-used agroindustrial residue with a high cellulose content. The corncob was milled and then delignified via the organosolve process in order to get the cellulose unbleached. An acid hydrolysis process was then carried out to obtain lignocellulose nanocrystals (LCNCs). Subsequently, LCNC/PP composites were obtained via termocompression molding using different concentrations of LCNC (0, 0.5, 1 and 2% by weight) previously mixed via extrusion. The residual lignin present in the LCNCs improved the compatibility between the reinforcement and the PP matrix. This was evidenced by the increase in mechanical properties and the stabilization of thermal properties. The results of the mechanical tests showed that the LCNC increases the tensile and flexural modules and strength with respect to neat PP. Composites with 2% of LCNC showed an increase of 36% and 43% in modulus and tensile strength, respectively, while the flexural modulus and strength increased by 7.6%. By using reinforcements of natural and residual origin (corncob) and improving the properties of recycled polymers, their reuse will increase, and this can lead to reducing waste in the environment. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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20 pages, 2673 KiB

Open AccessArticle

Carbon Sequestration via Bituminous Composites Containing Recycled High-Density Polyethylene

by Peyman Sadeghi, Ahmad Goli and Elham Fini

J. Compos. Sci. 2024, 8(3), 100; https://doi.org/10.3390/jcs8030100 - 11 Mar 2024

Viewed by 1038

Abstract

This paper presents an innovative bituminous composite containing recycled high-density polyethylene (HDPE) as a means of carbon sequestration. To prepare the composite, rejuvenators and recycled HDPE were introduced to reclaimed asphalt pavement (RAP), separately and in combination. To evaluate efficacy of rejuvenators, this study used the following three rejuvenators: waste engine oil (WEO), oleic acid (OA), and vacuum bottom (VB). The performance of the bituminous composite containing HDPE and rejuvenators was evaluated using the indirect tensile fatigue test, the rutting resistance test, the resilient modulus test, and the semi-circular bending test. Results showed that applying a combination of rejuvenators and recycled HDPE improved the resistance to fatigue, rutting, and cracking. Particularly, in terms of improving resistance to cracking, OA proved to be the most effective rejuvenator, followed by WEO and VB. In all bituminous composites studied here, the hybrid application of HDPE and rejuvenator proved to be more effective than the rejuvenator or HDPE alone. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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11 pages, 1995 KiB

Open AccessArticle

Reusing Bisphenol—A Type of Epoxy Polymer Recyclates from the Solvolysis of CFRP

by Ching Mui Cho, Xiaobai Wang, Sean Kenzo Tsumura, Warintorn Thitsartarn and Siok Wei Tay

J. Compos. Sci. 2024, 8(1), 2; https://doi.org/10.3390/jcs8010002 - 19 Dec 2023

Viewed by 1253

Abstract

Carbon fiber-reinforced polymer (CFRP) composites are highly functional composites which comprise two major components: the polymer matrix and the carbon fiber. Lightweight and having high strength, CFRPs have been used heavily in various industries such as wind, aerospace and automobile. The increasing demand and extensive use led to a huge quantum of CFRP waste from both end-of-life and during manufacturing. Out of this waste, only 2% is recycled, the rest are disposed of via incineration and/or landfill. This has raised significant environmental and sustainability concerns. The current state-of-the-art way of recycling CFRPs is by pyrolysis. However, through the pyrolysis process, the polymer used in the CFRPs, which accounts for around 65–75 wt.%, cannot be recovered and reused. In most publications, the focus on CFRP recycling was on the recovering of the more valuable carbon fiber. The polymer matrix is mostly burnt off, in the case of pyrolysis, or disposed. To obtain full circularity, recovering and reusing both the carbon fiber and polymer is necessary. In this paper, we primarily focus on the recovered bisphenol-A type of epoxy polymer (REP) obtained from solvolysis digestion of CFRP and explore the feasibility of reusing this REP by blending it with pristine epoxy in various compositions to create new materials. The physical and mechanical properties, including decomposition temperatures (T_d), glass transition temperatures (T_g), storage modulus, loss modulus, flexural and tensile strength, were characterized using thermal gravity analyzer (TGA), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and Instron universal tester. The results indicate a decrease in glass transition and decomposition temperature, and mechanical properties as the blending composition increases. This suggests that the total blending composition should not exceed 10 wt.%, with an optimal range potentially falling between 5 to 6 wt.%. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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13 pages, 1263 KiB

Open AccessArticle

Closed-Loop Recycling and Remanufacturing of Polymeric Aircraft Parts

by Marko Hyvärinen, Mikko Pylkkö and Timo Kärki

J. Compos. Sci. 2023, 7(3), 121; https://doi.org/10.3390/jcs7030121 - 15 Mar 2023

Cited by 2 | Viewed by 1997

Abstract

The aviation industry is facing the challenge of reducing fossil fuels and emissions. Fuel efficiency is improved by making efficient powerplant systems and lighter aircraft. Modern passenger aircraft utilize polymeric and polymeric composite materials to achieve lighter structures without compromising strength. The European Union already has legislation to prevent landfilling and to increase the use of recyclable materials in the automotive industry. While older-generation aircraft, made mainly from metallic materials, are easily dismantled and recycled into other uses, such a process does not yet exist for aircraft made from composite materials. In the coming years, the industry will have to answer the question of how retired polymeric composite aircraft structures are to be recycled. One solution to increase the life cycle of polymeric and polymeric composite parts would be closed-loop recycling. In this paper, a perspective of the closed-loop recycling of polymeric aircraft parts is discussed. The technical aspects of recyclability and the different business models for the remanufacture of a finger pinch shroud certified for use in Airbus A350-900 passenger aircraft are investigated. The results show that closed-loop recycling is possible for polymeric aircraft parts. Future studies could include studying an LCA between virgin and recycled materials for a certain part. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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17 pages, 18863 KiB

Open AccessArticle

Recycled Glass Polypropylene Composites from Transportation Manufacturing Waste

by Uday Vaidya, Sanjita Wasti, Halil Tekinalp, Ahmed Arabi Hassen and Soydan Ozcan

J. Compos. Sci. 2023, 7(3), 99; https://doi.org/10.3390/jcs7030099 - 06 Mar 2023

Viewed by 1257

Abstract

In recent years there has been growing interest in developing recycling technologies for composites manufacturing scrap, process waste and end-of-life parts. The focus of this work was to establish processing routes and mechanical property bounds for glass-polypropylene (PP-GF) scrap from the production of parts for truck trailers, automobiles, and rail cars. This study considered PP-GF scrap and demonstrated extrusion-compression molding (ECM) as a viable route for the closed-loop manufacture of composite parts. The results were promising in terms of the strength and modulus retention of the PP-GF recyclate. The tensile strength and modulus was the highest for 50% and 66% recycled content, compared with 100% and 83% recycle content. The flexural strength and modulus of the 100% and 83% recycled compositions was higher than the 66% and 50% recycled content, respectively. The impact energy absorption of the PP-GF recyclate at at all fiber loadings was superior in absorbing energy compared with the incumbent (benchmark) plywood. This work is useful to designers seeking to incorporate recycled materials in their products. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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13 pages, 2396 KiB

Open AccessArticle

Sustainable Composites from Waste Sulfur, Terpenoids, and Pozzolan Cements

by Katelyn A. Tisdale, Charini P. Maladeniya, Claudia V. Lopez, Andrew G. Tennyson and Rhett C. Smith

J. Compos. Sci. 2023, 7(1), 35; https://doi.org/10.3390/jcs7010035 - 11 Jan 2023

Cited by 7 | Viewed by 1258

Abstract

Sulfur cements have drawn significant attention as binders because sulfur is a byproduct of fossil fuel refining. Sulfur cements that can be formed by the vulcanization of elemental sulfur and plant-derived olefins such as terpenoids are particularly promising from a sustainability standpoint. A range of terpenoid–sulfur cements have shown compressional and flexural properties exceeding those of some commercial structural mineral cements. Pozzolans such as fly ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBFS) and abundant clay resources such as metakaolin (MK) are attractive fines for addition to binders. Herein, we report 10 composites prepared by a combination of sulfur, terpenoids (geraniol or citronellol), and these pozzolans. This study reveals the extent to which the addition of the pozzolan fines to the sulfur–terpenoid cements influences their mechanical properties and chemical resistance. The sulfur–terpenoid composites CitS and GerS were prepared by the reaction of 90 wt% sulfur and 10 wt% citronellol or geraniol oil, respectively. The density of the composites fell within the range of 1800–1900 kg/m³ and after 24 h submersion in water at room temperature, none of the materials absorbed more than 0.7 wt% water. The compressional strength of the as-prepared materials ranged from 9.1–23.2 MPa, and the percentage of compressional strength retained after acid challenge (submersion in 0.1 M H₂SO₄ for 24 h) ranged from 80–100%. Incorporating pozzolan fines into the already strong CitS (18.8 MPa) had negligible effects on its compressional strength within the statistical error of the measurement. CitS-SF and CitS-MK had slightly higher compressive strengths of 20.4 MPa and 23.2 MPa, respectively. CitS-GGBFS and CitS-FA resulted in slightly lower compressive strengths of 17.0 MPa and 15.8 MPa, respectively. In contrast, the compressional strength of initially softer GerS (11.7 MPa) benefited greatly after incorporating hard mineral fines. All GerS derivatives had higher compressive strengths than GerS, with GerS-MK having the highest compressive strength of 19.8 MPa. The compressional strengths of several of the composites compare favorably to those required by traditional mineral cements for residential building foundations (17 MPa), whereas such mineral products disintegrate upon similar acid challenge. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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11 pages, 2284 KiB

Open AccessArticle

Recycling Unrecycled Plastic and Composite Wastes as Concrete Reinforcement

by Nicholas Scarpitti, Nicholas Gavio, Alexander Pol and Seyed Hamid Reza Sanei

J. Compos. Sci. 2023, 7(1), 11; https://doi.org/10.3390/jcs7010011 - 05 Jan 2023

Cited by 1 | Viewed by 2022

Abstract

The land disposal of waste material is a major environmental threat, and recycling efforts must be exponentially improved to mitigate it. In this paper, a feasibility study was conducted to reinforce concrete with waste materials that are not typically recycled. Compression testing was performed to evaluate the mechanical properties of the concrete specimens. The results were compared with a conventional wire mesh reinforcement used in concrete. Alternative reinforcements that are typically disposed of in landfill were used, namely, plastic regrind, carbon fiber scraps, tempered glass, coarse aggregates, and wire mesh. For each reinforcement type, four specimens were manufactured to evaluate the consistency of the results. Cylindrical specimens with ASME standard dimensions of 10.16 cm × 20.32 cm were tested using a Tinius-Olsen compression testing machine after seven days of curing. A constant strain rate of 0.25 MPa/s was applied until a load drop of 30% was detected. The results show that, while the recycled reinforcements had lower compressive strengths than the wire mesh, they maintained a load-carrying capacity of more than 80%. A major improvement was observed in terms of the ductility and toughness of the reinforced concretes. The recycled-carbon-fiber-reinforced specimens showed 12% strain at failure, a major improvement in concrete ductility. The findings of this research indicate that such recycled particles and fibers without any post-processing can be used in the reinforcement of concrete, with a significant improvement in ductility. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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15 pages, 4982 KiB

Open AccessArticle

Recycled Carbon Nanofiber-Polypropylene Nanocomposite: A Step towards Sustainable Structural Material Development

by Abhishek Kumar Pathak and Tomohiro Yokozeki

J. Compos. Sci. 2022, 6(11), 332; https://doi.org/10.3390/jcs6110332 - 03 Nov 2022

Cited by 2 | Viewed by 1758

Abstract

Plastic products play a significant role in fulfilling daily necessities, but the non-decomposable nature of plastic leads to inescapable environmental damage. Recycling plastic material is the most appropriate solution to avoid pollution and short product lifespan. The present study shows the recycling effect on carbon nanofiber (CNF) reinforced polypropylene (PP) nanocomposite to attain the purpose of reuse and sustainability. 30 wt% CNF melt-blended with polymer and PP-nanocomposites were fabricated using the injection molding technique. PP-CNF nanocomposites were recycled, and mechanical, thermal, and morphological properties were investigated. Three-point bending and tensile testing showed a low decrement of ~1% and ~5% in bending and tensile strength after recycling 30 wt% PP-CNF nanocomposites. Scanning electron microscopy (SEM) images show that the alignment of CNF was disturbed after recycling due to the decrement in the aspect ratio of CNF. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) showed that the crystallinity of PP increases with recycling. The lowering of interfacial interaction between CNF and PP after recycling was studied by a stress-controlled rheometer. The decrement in mechanical properties of PP-CNF nanocomposite is not significant due to CNF reinforcement; hence, it can be reused for the same or other structural applications. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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16 pages, 3100 KiB

Open AccessArticle

Technical and Economic Viability of Distributed Recycling of Low-Density Polyethylene Water Sachets into Waste Composite Pavement Blocks

by Celestin Tsala-Mbala, Koami Soulemane Hayibo, Theresa K. Meyer, Nadine Couao-Zotti, Paul Cairns and Joshua M. Pearce

J. Compos. Sci. 2022, 6(10), 289; https://doi.org/10.3390/jcs6100289 - 30 Sep 2022

Cited by 3 | Viewed by 1987

Abstract

In many developing countries, plastic waste management is left to citizens. This usually results in landfilling or hazardous open-air burning, leading to emissions that are harmful to human health and the environment. An easy, profitable, and clean method of processing and transforming the waste into value is required. In this context, this study provides an open-source methodology to transform low-density polyethylene drinking water sachets, into pavement blocks by using a streamlined do-it-yourself approach that requires only modest capital. Two different materials, sand, and ashes are evaluated as additives in plastic composites and the mechanical strength of the resulting blocks are tested for different proportion mix of plastic, sand, and ash. The best composite had an elastic modulus of 169 MPa, a compressive strength of 29 MPa, and a water absorptivity of 2.2%. The composite pavers can be sold at 100% profit while employing workers at 1.5× the minimum wage. In the West African region, this technology has the potential to produce 19 million pavement tiles from 28,000 tons of plastic water sachets annually in Ghana, Nigeria, and Liberia. This can contribute to waste management in the region while generating a gross revenue of 2.85 billion XOF (4.33 million USD). Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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20 pages, 9552 KiB

Open AccessArticle

Investigation of the Mechanical Properties of Vinylester-Based Sheet Moulding Compound (SMC) Subject to Particle Recycling

by Vera Austermann, Jonas Neuhaus, Daniel Schneider, Rainer Dahlmann and Christian Hopmann

J. Compos. Sci. 2022, 6(3), 84; https://doi.org/10.3390/jcs6030084 - 08 Mar 2022

Viewed by 2733

Abstract

In light of climate change, fiber-reinforced plastics (FRP) are becoming increasingly important due to their lightweight construction potential. This benefit is additionally expanded on with the low cycle times, scrap rates and material costs of Sheet Moulding Compounds (SMC), making it the most often used material on the FRP market. While extensive studies regarding the recycling of SMC with unsaturated polyester-based matrices (UP-SMC) have been conducted in the past, this is not the case for vinylester-based SMC (VE-SMC). In this research, VE-SMC components were subject to a particle-recycling approach. Recyclate in the form of VE-SMC regrind was used to substitute SMC matrices during the compounding process. The dependence of the mechanical properties and failure behavior of VE-SMC containing regrind was investigated by means of microscopic and mechanical test methods for varying mass proportions of SMC regrind. Due to the addition of SMC regrind, a decreased fiber/matrix adhesion was observed. Furthermore, an increase in pore formation was observed with an increasing proportion of SMC regrind. The flexural modulus increased by 20% with a low percentage of regrind (ω_rSMC = 10 wt.%) in comparison to virgin SMC. In contrast, the tensile properties decrease (up to 30%) with the addition of SMC regrind independent of the investigated proportions of SMC regrind. Full article

(This article belongs to the Special Issue Recycled Polymer Composites: Futuristic Sustainable Material)

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