Recycled Plastic Research Articles

Experimental Study on the Mechanical Properties of Sustainable Concrete using Recycled Plastic and Glass Waste

This study explores using recycled waste glass and plastic fibers as substitutes for fine aggregates in concrete to meet the growing need for sustainable building materials. The basic materials consist of OPC 43 grade and locally obtained river sand. The research incorporates glass powder from crushed beer bottles and plastic fibers from recycled plastic bottles into the concrete mixture. Various tests, including slump, compressive strength (CS), and split tensile strength (STS) assessments, are performed to ascertain the characteristics of the modified concrete in both its fresh and hardened states. The findings demonstrate a significant enhancement in the ease of handling when glass powder is used, exhibiting a surge of 170% and 270% for mixtures, including 15% and 25% glass powder, respectively, compared to conventional OPC concrete. Although including these recycled materials reduces compressive strength (19.95% for SP15 and 21.39% for SP25); tensile strength is significantly improved, with gains of 35% for SP15 and 53.75% for SP25. This research emphasizes the feasibility of integrating waste glass and plastic fibers into concrete as a practical method for sustainable building.

A green and efficient method to prepare oleic acid–modified CaCO3/reHDPE composites

Industrial recycling of waste plastics frequently utilizes mechanical recovery and recycling. However, plastics recycled through mechanical recovery tend to have reduced properties, limiting their applications. In this study, modified calcium carbonate (OA-CaCO3) was prepared using different amounts of oleic acid (OA) (0.5, 1.0, and 2.0 wt%). Infrared spectroscopic characterization showed OA was successfully adsorbed on the CaCO3 surface. Particle size, micromorphology, oil absorption value, and activation tests indicated that CaCO3 modified with 1.0 wt% OA yielded optimal results. Melt blending 1.0 wt% OA-modified CaCO3 with recycled high-density polyethylene (reHDPE) produced composites. Scanning electron microscopy results showed OA modification enhanced interfacial compatibility between the two phases. Mechanical property tests revealed at high filling levels, the impact strength of OA-modified composites increased considerably, reaching 42.6 kJ/m2 with 40 wt% OA-CaCO3 filling. Melt flow rate test results showed that OA-modified composites had increased melt flow and modified processing properties. Filling OA-CaCO3 to compensate for reHDPE properties caused by mechanical recycling is essential to expand mechanical recycling applications in plastics recycling.

Recycling of puffed polystyrene beads waste as a low‐cost antifouling ultrafiltration membrane for water purification

AbstractCurrently, plastic waste, limited water resources, and water contamination are challenges of universal concerns. Recycling plastic waste as a membrane for water/wastewater treatment is of great significance from the perspective of environmental protection and safe drinking water supply. In this study, we used for the first time the puffed polystyrene beads waste (PPSBW) as a basic material for the fabrication of an ultrafiltration membrane and Pluronic F127 (PF127) as a plasticizer and hydrophilizing agent. Different ratios of PF127 were added to the casting solution, and the characteristics of the blank PPSBW and PF127‐modified membranes (PPSBW‐PF127) were evaluated in detail. The addition of PF127 increased the turbidity and viscosity of the casting solution, decreased the contact angle (increased the hydrophilicity), decreased the pure water flux, and increased the rejection of humic acid. The PPSBW membrane with 3 wt.% of PF127 showed the highest antifouling properties, the highest cleaning efficiency, and kept a satisfactory BSA and pure water flux for 4 runs. Overall, PF127 improved the hydrophilicity, organic matter separation, and enhanced the antifouling properties of the PPSBW‐derived membrane.Highlights Renew flow: Repurposing plastic waste as a UF membrane was successfully achieved. The PPSBW‐PF127 membrane was applied for wastewater treatment. Mechanical properties showed reasonable response by adding Pluronic F127. The PPSBW‐PF127 membrane demonstrated a significant rejection and permeability. The PPSBW‐PF127 membrane showed the highest antifouling and cleaning properties.

Click dechlorination of halogen-containing hazardous plastics towards recyclable vitrimers.

Amid the ongoing Global Plastics Treaty, high-quality circulation of halogen-containing plastics in an environmentally sound manner is a globally pressing issue. Current chemical dechlorination methods are limited by their inability to recycle PVC at the long-chain carbon level and the persistence of eco-toxic organochlorine byproducts. Herein, we propose a click dechlorination strategy for transforming waste PVC into valuable vitrimers via a one-step cascade thiol-ene click reaction and dynamic polymerization. Thermal activation of C-Cl bonds initiates β-elimination dechlorination, while disulfide bonds synchronously undergo homolytic cleavage, generating sulfur-centered radicals that drive precise sulfur-chlorine substitution and the formation of disulfide dynamic networks. This strategy achieves nearly complete chlorine extraction (93.88%) and produces vitrimers with tailorable mechanical and reprocessing properties, spanning from soft elastomers with 784% elongation to rigid plastics with a yield strength of 34 MPa. The significant advantage of this strategy is backbone protective precise dechlorination, enabling ecosystem toxicity reduced by 99.51% compared with widely adopted pyrolysis methods. This work introduces a sustainable pathway for upcycling PVC into valuable materials, marking significant progress in chlorinated plastic recycling.

Preparation of hemp‐based biocomposites and their potential industrial application

AbstractBiocomposites are an emerging field in plastic industry. The incorporation of agri‐food waste in conventional or biobased polymer matrices allows the industry to lessen its carbon footprint, while producing recyclable plastic products. In this work, hemp hurd, a byproduct of hemp fiber production process, was used as a filler to prepare novel compostable composites in two different loadings (22% and 32% w/w respectively). Waste hemp hurds were selected due to their abundance and the lack of derived high‐value products. Three different polymers were used, namely poly[(tetramethyleneadipate)‐co‐(tetramethyleneterephthalate)] (PBAT) and poly(tetramethylene succinate) (PBS) as compostable polymers and a polyethylene elastomer for comparison. The bare polymers and prepared blends were then characterized for their structure and morphology by XRD and FESEM, as well as for their wettability, thermal and mechanical properties (namely energy absorbed on impact and flexural modulus). Structural and morphological characterization unveiled the different interactions occurring between hemp and the polymer matrices, suggesting the major impact of the type of used polymer when compared with biomass loading percentages. Mechanical tests showed that both PBAT and PBS blends properties are comparable to those of the pure polymers (i.e., in the case of PBAT the flexural modulus of the pure polymer was 82.2 MPa while the hemp‐loaded blends stood at around 50 MPa, whereas all PBS polymers and blends were 220 MPa, with no statistical difference between samples). These biomaterials have also similar thermal properties with respect to the bare polymers, underlining the promising potential as sustainable alternative to pure polymers.Highlights Waste hemp hurds were used to load biodegradable polymers at different percentages. Hemp hurd‐based biomaterials with excellent properties were prepared. Polymer flexural behavior was maintained even after hemp addition. Polymer‐hemp interactions for each polymeric matrix were elucidated. Hemp substitutes up to 32% w/w of polymer without affecting its properties.

Circular Economy and Chemical Conversion for Polyester Wastes.

Polyester waste in the environment threatens public health and environmental ecosystems. Chemical recycling of polyester waste offers a dual solution to ensure resource sustainability and ecological restoration. This minireview highlights the traditional recycling methods and novel recycling strategies of polyester plastics. The conventional strategy includes pyrolysis, carbonation, and solvolysis of polyesters for degradation and recycling. Furthermore, the review delves into exploring emerging technologies including hydrogenolysis, electrocatalysis, photothermal, photoreforming, and enzymatic for upcycling polyesters. It emphasizes the selectivity of products during the polyester conversion process and elucidates conversion pathways. More importantly, the separation and purification of the products, the life cycle assessment, and the economic analysis of the overall recycling process are essential for evaluating the environmental and economic viability of chemical recycling of waste polyester plastics. Finally, the review offers perspective into the future challenges and developments of chemical recycling in the polyester economy.

Selective Degradation of Polyethylene Terephthalate Plastic Waste Using Iron Salt Photocatalysts.

Plastic pollution poses a significant challenge to environmental conservation. Efficient recycling of plastic is a key strategy to address this issue. Polyethylene terephthalate (PET), commonly found in plastic bottles, represents a substantial portion of plastic waste. Consequently, the efficient degradation and recycling of PET is crucial for the sustainable development of society. However, the implementation of methods for PET depolymerization and recycling typically necessitates alkaline/acidic pre-treatment and significant energy input for heating. Here, we propose a gentle, and highly efficient photocatalysis approach for selectively degrading PET plastic waste into terephthalic acid (TPA) in high yield (up to 99%) using cost-effective iron salts. Notably, this method achieved excellent selectivity with high TON and TOF values, applying oxygen or air as environmentally friendly oxidants. In addition, the solvent can be recycled without compromising the TPA yield, and large-scale reactions can be performed smoothly.

Fire parameters of recycled plastic pellets

AbstractDuring the recycling process, waste plastic undergoes various processes that change its geometry. The thermal properties and fire behaviour of plastic in different geometries has not been widely studied. This paper aims to determine critical thermal properties of plastic pellets made of recycled plastic. For this paper, cone calorimeter tests of various volumes of recycled plastic pellets of low‐ and high‐density polyethylene and polypropylene were conducted. During these tests, the heat release rate (HRR), mass loss rate and time‐to‐ignition were measured, thereafter the heat of combustion (HOC) was calculated. A calibration of suitable time‐to‐ignition equations is carried out. The average HRR is between 353 and 581 kW/m2 with an external heat flux of 50 kW/m2. The measured time‐to‐ignition values ranged between 27 s at 50 kW/m2 and just more than 90 s at 25 kW/m2. Values obtained analytically from the thermally thin time‐to‐ignition equations for these materials describe ignition well, which appears to be due to the particulate nature of the samples. The HOC (40–41 MJ/kg) shows good agreement with the HOC for virgin plastic found in literature. These properties can be used as a basis for material characterisation, and further testing will be done before using this as simulation inputs to determine how bulk stored plastic pellets will behave in the event of a fire.

The Properties of Bricks Made from Recycled HDPE

Plastic waste, particularly high-density polyethylene (HDPE), poses significant environmental challenges due to its non-biodegradable nature. Recycling HDPE into building materials, such as bricks, offers a sustainable solution to mitigate these impacts. This study investigates the properties of bricks made from recycled HDPE, focusing on their compressive strength, water absorption, and durability. The results indicate that HDPE bricks exhibit superior mechanical properties, including higher compressive strength and lower water absorption compared to traditional clay bricks. These bricks are lightweight, cost-effective, and demonstrate excellent durability, making them a viable alternative for sustainable construction. The research highlights the potential of recycled HDPE bricks in reducing plastic waste and promoting environmental sustainability. The intensifying generation of plastic waste presents a significant environmental challenge worldwide. Plastic waste, due to its non-biodegradable nature, contributes to land and water pollution, requiring the exploration of sustainable waste management solutions. Recycling plastic waste into building materials, such as bricks, offers a potential solution to mitigate environmental impacts. This research aimed to investigate the integration of plastic waste into building materials through a comprehensive study using experimental testing, software analysis, and structural design. The ETAB analysis demonstrated that the HDPE model exhibited lower bending moments and axial loads compared to the concrete model, suggesting superior mechanical properties and load-carrying capacity. This research contributes to the understanding of the behaviour and performance of plastic bricks in structural applications, enabling the development of sustainable and efficient building designs that incorporate plastic waste materials. Key Words: Plastic Waste, Environmental Challenge, Non-Biodegradable, Sustainable Solutions, Experimental Study, Plastic Bricks, Alternative Building Materials, Methodology, Comparable Strength, Plastic Waste Crisis.

Photooxidation of Polystyrene into High‐Value Chemicals

Plastics play a crucial role in the survival and advancement of human civilization. However, the increasing challenge of plastic pollution presents significant obstacles. Disposal methods such as incineration and landfilling result in substantial resource wastage and pose potential environmental hazards. The slow progress in recycling and reusing waste plastics hinders their industrial application and effective response to environmental crises. Photocatalysis offers promising solutions for the future of plastic recycling, particularly with the recent increase in photocatalytic degradation methods for polystyrene (PS). This review provides a comprehensive overview of the latest advancements in the photooxidation of PS into high‐value chemicals.

Super Tough PA6/PP/ABS/SEBS Blends Compatibilized by a Combination of Multi-Phase Compatibilizers.

Development of multi-component blends to prepare high-performance polymer materials is still challenging, and is a key technology for mechanical recycling of waste plastics. However, a multi-phase compatibilizer is prerequisite to create high-performance multi-component blends. In this study, POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) compatibilizers are prepared via melt-grafting of maleic anhydride (MAH) and styrene (St) dual monomers to polyolefin elastomer (POE) and poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), respectively. Subsequently, these compatibilizers are utilized to compatibilize the PA6/PP/ABS/SEBS quaternary blends through melt-blending. When POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) are added, respectively, both can promote the distribution of the dispersed phases, significantly reducing the dispersed phase size. When adding 10 wt% POE-g-(MAH-co-St) and 10 wt% SEBS-g-(MAH-co-St) together, compared to the non-compatibilized blend, the fracture strength, fracture elongation, and impact strength surprisingly increased by 106%, 593%, and 823%, respectively. It can be attributed to the hierarchical interfacial interactions which facilitate gradual energy dissipation from weak to strong interfaces, resulting in the improvement of mechanical properties. The synergistic effect of the enhanced phase interfacial interactions and toughening effect of elastomer compatibilizer achieved simultaneous growth in strength and toughness.

Plastic waste in dense asphalt mixes for road pavements

Recycling plastic waste in asphalt pavements records increasing statistic figures of application during the last decade worldwide. Due to environmental constraints, but also, to some beneficial properties of plastic waste, recycling in asphalt tends to become current practice, in several countries. In the Aristotle University of Thessaloniki (AUTH), the first attempt to produce asphalt mix using plastic waste consisted of mixing recycled plastic flakes with non-modified binder. Following an asphalt mix design in the laboratory, the whole mass of conventional aggregates was replaced by PET flakes. Recycled PET flakes were chosen to be introduced in the asphalt mix since they are hard, resilient and water repellent. Bitumen emulsion was first preferred as a binder to produce a cold asphalt mix. At a second stage of experimental research, plastic flakes replaced a part of the limestone sand while conventional asphalt 50/70 was used as a binder. At this stage, the experimental research provided more encouraging outcomes. Stability of asphalt mixes decreases as the plastics content in the mix increases, but all recorded values were still within limits of acceptance. At a third stage of research, LDPE recycled material of fine gradation was used to replace a part of the asphalt binder in dense mixes. The objective was to produce a modified binder and a more durable asphalt structure. Test results showed a significant improvement of the performance of asphalt mixes, in terms of strength and deformability of the asphalt mix structure. The research is completed by comparing the conventional techniques with the outcomes of the recycling process and by delineating potential fields of application of the recycled plastics in asphalt pavements.

Effects of acid and sulphate attack on concrete containing recycled plastic waste fine aggregate

Effects of acid and sulphate attack on concrete containing recycled plastic waste fine aggregate

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

The introduction of nitrogen vacancies (VN) and iron (Fe) single atoms sites significantly enhances the visible light absorption and charge transfer ability of carbon nitride (CN) catalysts. This paper presents the successful synthesis of a VN-rich, Fe single atoms incorporated CN, a catalyst that demonstrates exceptional degradation performance and cycling stability. The 2-mercaptobenzothiazole (MBT) removal rate by 20Fe-CN reached 99.51% within just 11min under visible light, and the catalyst maintained superior photocatalytic performance upon repeated use. Additionally, the 20Fe-CN/Photo/High-temperature system effectively converted polystyrene (PS) to benzoic acid (BA), achieving a BA yield of 19.73% after 48hours. Under visible light irradiation, the VN sites captured electrons and facilitated their rapid transfer to neighboring Fe sites, enhancing the photocatalytic redox processes. This study also identified ·O2- as the primary active species in the photocatalytic process. This research supports the development of diverse single-atom modified carbon nitride photocatalysts, holding significant potential for wastewater treatment and plastic resource recycling, and providing valuable insights for future photocatalysts in environmental remediation.

Sustainable supply chain management challenges analysis in local plastic recycling business

Sustainable supply chain management (SSCM) has become the key concept for every industry in managing their supply chain system by focusing on three aspects: economics, social, and environmental. Even though the implementation of SSCM will help the industry increase the efficiency of supply chain management, some challenges make the firms cannot implement the SSCM concept well and unsuccessful. The challenges of SSCM implementation need to be identified and managed to overcome these challenges and increase the efficiency of SSCM management. Therefore, this study aims to identify and analyze the challenges to SSCM implementation in the case of the local plastic recycling business in Thailand. The questionnaire was used to collect data from plastic recycling business experts. The best-worst method was used to analyze the significant challenges and prioritize ranking the SSCM implementation challenges. The results of this research found that management challenges are the first rank which lack of the policy and strategy for SSCM is a critical sub-challenge in the management dimension. The financial challenges are the second rank for SSCM due to the local plastic recycling business still being faced with financial constraints, which is the critical sub-challenges in the financial dimension, and the technology challenges are ranked last, which presented that it is less critical for SSCM in the local scale. Furthermore, the research conclusion and the guideline for the research direction of this research are presented

From Flourish to Nourish: Cultivating Soil Health for Sustainable Floriculture.

Despite its rapid growth and economic success, the sustainability of the floriculture industry as it is presently conducted is debatable, due to the huge environmental impacts it initiates and incurs. Achieving sustainability requires joint efforts from all stakeholders, a fact that is often neglected in discussions that frequently focus upon economically driven management concerns. This review attempts to raise awareness and collective responsibility among the key practitioners in floriculture by discussing its sustainability in the context of soil health, as soil is the foundation of agriculture systems. Major challenges posed to soil health arise from soil acidification and salinization stimulated by the abusive use of fertilizers. The poisoning of soil biota by pesticide residues and plastic debris due to the excessive application of pesticides and disposal of plastics is another significant issue and concern. The consequence of continuous cropping obstacles are further elucidated by the concept of plant-soil feedback. Based on these challenges, we propose the adoption and implementation of several sustainable practices including breeding stress-resistant and nutrient-efficient cultivars, making sustainable soil management a goal of floriculture production, and the recycling of plastics to overcome and mitigate the decline in soil health. The problems created by flower waste materials are highlighted and efficient treatment by biochar synthesis is suggested. We acknowledge the complexity of developing and implementing the proposed practices in floriculture as there is limited collaboration among the research and operational communities, and the policymakers. Additional research examining the impacts the floriculture industry has upon soils is needed to develop more sustainable production practices that can help resolve the current threats and to bridge the understanding gap between researchers and stakeholders in floriculture.

Exploratory analysis of influential factors in the choices of using single-use or reusable cups in vending

PurposeThis study investigates the variables that play a role in the purchase intention of a hot beverage at a vending machine (1) served in a 100% recyclable plastic single-use cup, (2) served in a biodegradable paper single-use cup and (3) served in personal, reusable cups brought by customers. The variables considered are perceived environmental benefits (PEBs), perceived contamination risk (PCR), social norms (SNs), value for money (VM), gender and age. The secondary objective is to investigate respondents’ perceptions of these cups using the first four variables and to assess the existence of significant differences among them.Design/methodology/approachFor the first purpose, three separate logistic regression models on purchase intention were created, considering PEBs, PCR, SNs, VM, gender and age as independent variables. For the second purpose, the analysis relied on Friedman’s nonparametric test. The entire survey was conducted in Italy on a sample of 1,006 consumers.FindingsSNs and VM are the variables with the greatest influence on final purchase intention. PEBs seem to have an effect only in the case of the plastic and paper single-use cups, while PCR only in the case of the reusable cup. Neither gender nor age seem to play a significant role in final purchase intention. Friedman’s test revealed significant differences among the three cup types in terms of perceptions, but not in the case of the PCR variable.Originality/valueThe study is the first to compare new single-use cups with reusable cups from vending machines in terms of consumers’ perceptions and preferences.

Dynamic covalent epoxy network of hyperbranched-synergistic-supramolecular: Catalyst-free reprocessing, and application in carbon fiber composites recycling

Plastic recycling, especially the recycling of thermosets, is a crucial step towards improving waste management and achieving economic recycling. Here, a method utilizing non-covalent supramolecular interactions and synergistic hyperbranched structures is reported to endow transesterification-based thermosetting materials with recyclability in the absence of a catalyst. A hyperbranched epoxy resin curing agent (HPCA) containing amide bonds, terminated by amine and ester, was designed and synthesized, and further cured with bisphenol A epoxy resin. The hyperbranched topological structure and its abundant amide bonds contribute to the formation of a dense hydrogen bonding network, enhancing the reprocessability, thermal, and mechanical properties of the material. As a result, the resin can be reprocessed by hot pressing at 190 °C and 10 MPa for 40 min without catalyst. Moreover, amide and ester bonds endow resin materials with excellent degradation performance in alkaline solutions, laying the foundation for the recycling and utilization of carbon fibers in composite materials.

Recycling of Plastics in the Automotive Sector and Methods of Removing Paint for Its Revalorization: A Critical Review.

The presence of plastics in the automotive industry is increasingly significant due to their lightweight nature, which contributes to reducing fuel consumption and CO2 emissions while improving versatility and mechanical properties. Polypropylene (PP) and other polyolefins are among the most commonly used materials, especially for components such as bumpers. The use of composite materials, i.e., a combination of different polymers, improves the properties through synergistic effects, thereby also improving the performance of the final product. In the automotive industry, PP reinforced with 20% talc or CaCO3 is commonly used. The mechanical recycling of polypropylene bumpers is the most common type of recycling. However, challenges arise during this process, such as the presence of impurities like paint, chemical contaminants from previous use, and polymeric impurities from different polymers mixed into the polymer matrix, among others. Paint affects both the aesthetic quality and the mechanical and intrinsic properties of the recycled material. This review aims to analyze the main methods reported in the literature, focusing on those with low environmental impact. Furthermore, these methods are classified according to their capacity, effectiveness, substrate damage, environmental hazards, and economic feasibility. It also aims to offer a comprehensive overview of the mechanical recycling of plastic waste in the automotive industry.

Attitude of Romanian students and their families concerning waste management

Abstract Waste recovery, recycling included, is an important step in waste management, preceding final disposal. In 2018, according to Eurostat, the recycling rate of municipal waste was 47% in the European Union and only 11.1% in Romania. Thus governmental institutions have implemented new measures in order to reduce environmental pollution by ineffective waste management. In 2022, 535 students aged 22-24.5 years, males and females, studying in Craiova (one of the six largest academic cities of Romania), were asked to answer an 18-item questionnaire regarding their and their families’ attitude towards waste recycling. Most of the students (60.7%) were residents in the university city, while the others - in smaller cities or in villages of the region. Only 38.3% of the subjects (N = 205) declare their families recycle waste; the most common excuse for no-recycling (37.8%) is the lack of recycle bins in the house proximity. Only 20 families (3.7%), all of them living in Craiova, take the fried oil to collecting points in supermarkets; most of the others eliminate it in the sewerage system, especially those from outside the city (p < 0.01). Seventy-five students (14%) are not able to mention any recent measure taken by the government in order to reduce plastics environmental pollution; the others discuss about the increased number of recycle bins around the city (53.2%), recycling of single-use plastics (34.5%) or use of biodegradable bags (25.2%). No-recycling (42%), using daily his/her own car (18.7%, p < 0.01 males vs. females), using too much plastics (11.2%) are the most frequent self-reported students’ disregards for the environment. Most of the subjects consider environmental health of essential importance (88.7%) and would like to participate in environment protection actions (92.5%). Romanian students seem to have a positive attitude and like to be involved in the environment protection, without a significant influence regarding the gender and the residence place. Key messages • Education and information are essential tools to make people ecologically aware. • Recycling is one of the best ways to have a positive impact on both natural and community environment.