Virgin Counterparts Research Articles

BUCKLING BEHAVIOUR OF HIGH-STRENGTH RETROFITTED STEEL SECTIONS MANUFACTURED BY POST HEAT-TREATMENT PROCESSES

High-strength steel is increasingly popular in construction for its strength-to-weight ratio, which lowers the self-weight of structures and reduces transportation, erection, and foundation costs. Induction hardening (IH) process which involves rapid heating and cooling of the material leads to microstructural changes which enhance the hardness and strength of conventional steel, elevating it to the level of High Strength (HS) steel. This study reports an extensive investigation on the buckling response and design of IH post-treated structural steel Circular Hollow Sections (CHS). It includes tensile coupon tests, microstructural analyses, initial geometric imperfection measurements, and residual stress evaluations to determine the effects of IH treatment on CHS. Column buckling tests were conducted, and a numerical model was developed and validated against the experimental results which was utilised to study systematically the effect of imperfections. The findings suggest that the magnitude of the imperfections in IH steel sections doubled compared to the non-treated condition, whilst there was a minimal impact on the residual stresses. A comprehensive parametric study was performed using finite element models to study the structural response of IH steel CHS columns over a large range of global slendernesses and allow the assessment of the buckling curves specified in EN 1993-1-1. It was concluded that the buckling curve ‘a’ (imperfection factor, α=0.21) specified in EN 1993-1-1 provides the best buckling load predictions for the IH steel CHS columns, the response of which is superior to that of their virgin counterparts, despite the increased imperfections caused by the heat-treating process.

Grafting of maleic anhydride onto waste acrylonitrile butadiene styrene (ABS) and its application for compatibilization of ABS blends

AbstractIncorporating recycled plastics into the manufacturing process is an essential way to establish a sustainable plastics economy. However, current processes are limited by the degradation of mechanical properties, high cost, and inconsistent product quality compared with their virgin counterparts. Here, we present an upcycling strategy for waste plastics where waste acrylonitrile‐butadiene‐styrene (reABS) is first grafted with maleic anhydride (MAH), then utilized to compatibilize nylon 6(PA6)/ABS and PA6/ABS/CaCO3 blends. The reABS‐g‐MAH exhibits improved Young's modulus and tensile strength, but lower strain at break and impact strength compared with reABS. As an additive, reABS‐g‐MAH effectively compatibilizes PA6/ABS and PA6/ABS/CaCO3 blends, indicated by greatly decreased PA6 domain size, homogeneous dispersion of fillers, and narrowed glass transition temperature regions between PA6 and ABS. Adding only 5 wt% reABS‐g‐MAH increases the Young's modulus, strain at break, and impact strength of PA6/ABS blends by 26%, 180%, and 110%, respectively, compared with uncompatibilized samples. Similarly, for PA6/ABS/CaCO3 blends, the strain at break and impact strength increase by 370% and 150%, respectively, while the Young's modulus and tensile strength show increases of 5% and 10%. The results show that this strategy of using polar groups to functionalize waste plastics as compatibilizers may open numerous opportunities for upcycling waste plastics.

Effects of Powder Reuse and Particle Size Distribution on Structural Integrity of Ti-6Al-4V Processed via Laser Beam Directed Energy Deposition

In metal additive manufacturing, reusing collected powder from previous builds is a standard practice driven by the substantial cost of metal powder. This approach not only reduces material expenses but also contributes to sustainability by minimizing waste. Despite its benefits, powder reuse introduces challenges related to maintaining the structural integrity of the components, making it a critical area of ongoing research and innovation. The reuse process can significantly alter powder characteristics, including flowability, size distribution, and chemical composition, subsequently affecting the microstructures and mechanical properties of the final components. Achieving repeatable and consistent printing outcomes requires powder particles to maintain specific and consistent physical and chemical properties. Variations in powder characteristics can lead to inconsistencies in the microstructural features of printed components and the formation of process-induced defects, compromising the quality and reliability of the final products. Thus, optimizing the powder recovery and reuse methodology is essential to ensure that cost reduction and sustainability benefits do not compromise product quality and reliability. This study investigated the impact of powder reuse and particle size distribution on the microstructural and mechanical properties of Ti-6Al-4V specimens fabricated using a laser beam directed energy deposition technique. Detailed evaluations were conducted on reused powders with two different size distributions, which were compared with their virgin counterparts. Microstructural features and process-induced defects were examined using scanning electron microscopy and X-ray computed tomography. The findings reveal significant alterations in the elemental composition of reused powder, with distinct trends observed for small and large particles. Additionally, powder reuse substantially influenced the formation of process-induced defects and, consequently, the fatigue performance of the components.

Promoting sustainability: Micellization and surface dynamics of recycled monoethanolamine surfactants

The purpose of this work is to explore the micellization and surface characteristics of recycled monoethanolamine (MEA) surfactants, designated as MK-1, MK-2, and MK-3, and to assess their potential in promoting sustainability. Traditional surfactants contribute to environmental pollution due to their non-renewable sources and persistence in nature. This study addresses the knowledge gap in sustainable surfactant development by investigating the efficacy of recycled MEA surfactants. Its novelty lies in its innovative recycling process, which not only reduces waste, but also produces surfactants with superior properties. This study also investigates the distillation-based separation of MEA from degraded compounds, showcasing its potential in waste management. It was found that a maximum MEA separation of 17 % was achieved with a resulting purity of 83 %. Optimal conditions, including the use of catalysts and a temperature of 393K, led to enhanced oleic acid conversion. Similarly, reactions conducted with catalysts at 433K for 3 h demonstrated favorable outcomes. Surfactant MK-1 exhibited superior foam and emulsifying abilities, generating a foam height of 60 cm with only 8 cm lost after 10 min. Regarding emulsifying properties, the sunflower oil/water system with a 0.1% MK-1 solution exhibited delayed water separation from the emulsion. MK-3 displayed the highest pC20 value at 2.91. Among the MEA-based surfactants, MK-1 reduced surface tension to 33.1 mN/m. The maximum surface excess concentration (Γmax) for all surfactants was consistent. This demonstrates that recycled MEA surfactants exhibited favorable micellization properties, with a critical micelle concentration (CMC) comparable to that of virgin counterparts. Over ten cycles of use and regeneration, the performance of recycled MEA surfactants remained stable. Surface tension measurements indicated improved interfacial activity, while emulsification capacity tests revealed an enhanced performance in forming stable emulsions. This implies the potential of recycled MEA surfactants to produce high-performance surfactants, thereby promoting sustainability in the chemical industry.

Immiscible Polymer Blends Made from Industrial Shredder Residue Mixed Plastic with and without Melt Blending.

The processing of an immiscible polymer blend using melt blending (i.e., extrusion) often results in a polymer material with inferior mechanical performance compared with its virgin counterparts. Here, we report and compare the properties of immiscible polymer blends produced from industrial mixed plastic waste from shredder residue comprising at least four different polymers (acrylonitrile butadiene styrene, polystyrene, polypropylene, and polyethylene) with and without a prior melt-blending step employed. As anticipated, mixed plastic blend produced with a prior melt-blending step exhibited a more homogeneous microstructure, resulting in brittleness, poor work of fracture, and single-edge notched fracture toughness with a flat R-curve. Without the intimate polymers mixing arising from melt blending, the resulting mixed plastic blend was found to possess a more heterogeneous concentric ellipsoid microstructure with large single polymer domains. This mixed plastic blend demonstrated progressive failure under uniaxial tensile loading, along with a more ductile single-edge notched fracture toughness response accompanied by a growing R-curve. Digital image correlation and fractographic analysis revealed that melt blending created a large number of incompatible polymer boundaries that acted as stress concentration points, leading to brittleness and earlier onset catastrophic failure. The more heterogeneous mixed plastic blend produced without using a prior melt-blending step contains a smaller number of incompatible polymer boundaries. Additionally, the presence of larger single polymer domains also implies that the mechanical characteristics of the single polymer can be exploited in the immiscible mixed plastic blend. Our work opens up a simple pathway to add value to mixed plastic waste from shredder residue for use in engineering applications, diverting them away from landfill or incineration.

Fatigue performance of ECC link slab incorporated full RC girder joint-free bridges

The use of link slab (LS) made of Engineered Cementitious Composite (ECC) in the construction of joint-free bridge deck can meet structural performance requirements and enhance durability to minimize life cycle costs. Studies documented in the literature to date have been limited to composite steel-concrete I-deck girder bridges despite their commonly used reinforced concrete (RC) girder counterparts in construction. This paper deals with two span full RC deck girder joint-free bridges with ECC link slab (ECC-LS) constructed and tested under static and fatigue loading up to 1,000,000 cycles at 4 Hz subjected to mean stress level of 40% of girder ultimate load, followed by post-fatigue static loading to failure. Residual load, deflection, moment, rotation, stiffness, and energy absorbing capacity of fatigued bridge specimens are compared with its virgin (non-fatigued) counterparts to assess structural performance. Experimental moment capacities are compared with those obtained from existing analytical equations. The comparative performance of joint-fee bridge with RC deck girder is compared with its composite steel-concrete I-girder counterpart to assess its feasibility of construction.

Recycle waste PET yarn on site by feeding waste yarn as grinded powder to improve product quality, increase energy efficiency and reduce environmental impact

A technical approach was proposed to recycle waste PET yarn on site with the aim of building green manufacturing plant with no waste accumulation. In the recycling process, the waste PET yarn with almost infinite aspect ratio was first treated with custom-designed grinder prior to recycling, which breaks the yarn into small pieces and produce powder-like final product (waste yarn/fiber powder, WYP/WFP). Then it could be mixed with PTA and EG to form slurry and fed into manufacturing unit using well-established method rather than be fed as melt by screw-extruder that is known for its high energy intensity. Furthermore, the wetting of WYP by EG during slurry formation facilitates the de-oxygenation process and is beneficial to improve the quality of product, which produces higher quality products with lower cost compared to conventional methods. PET containing 20 wt.% WYP addition using the proposed technical approach could give best balance between performance and profit margin. The properties of the produced PET products (20% WYP addition) were found similar to that of virgin counterparts and meet the specs for various commercial application. With the help of energy benign treatment and feeding processes, the energy intensity and CO2 emission of this method compared to conventional method were reduced by 78.96% and 62.02%, respectively. The method proposed a novel energy efficient and cost-effective approach to reliably recycle waste PET to high quality PET products on site. It partially solves the problems that the industry currently encountered, such as high recycle cost, relatively low product quality, high energy intensity and low economic benefit. It moves one step forward to the greening of the manufacturing process and may help on the sustainable development of the PET industry.

Magnetothermal soft actuators from recycled face mask materials

Polymeric soft actuators offer numerous advantages such as lightweight, compactness, safety and versatility, making them suitable for applications requiring delicate manipulation and adaptability. However, their susceptibility to wear and degradation results in a shorter service life compared to conventional metallic actuators, leading to increased waste generation. To address this issue, this paper presents a sustainable approach to utilising waste materials, specifically repurposing stretchable strings from used disposable facemasks, to create magnetic nanoparticles infused yarn actuators. An innovative infusion technique is presented to aid in the scalable manufacturing of high-volume magnetic yarn actuators. The developed actuators demonstrate magnetothermally induced linear actuation comparable to their virgin counterparts. The actuators are fabricated in different structures, including braided-straight, braided-twisted and braided-coiled, with the coiled configuration showing the highest actuation strain and straight yarn generating maximum stress. The technology also proves to be energy-efficient compared to the prior art, making it suitable for various applications including soft robotics, compliant exoskeletons, smart prostheses and e-textiles. Repurposing abundant waste materials into soft actuators offers a promising solution for managing waste generated from end-of-service soft devices.

The role of prolactin in the suppression of the response to restraint stress in the lactating mouse.

Suppression of the hypothalamic-pituitary-adrenal (HPA) axis is a well-characterised maternal adaptation that limits the exposure of the offspring to maternally-derived stress hormones. This current study has investigated the possible involvement of the lactogenic hormone, prolactin, in this physiologically important adaptation. As expected, circulating prolactin levels were higher in unstressed lactating mice compared to their virgin counterparts. Interestingly however, the ability of an acute period of restraint stress to further elevate prolactin levels was diminished in the former group. The stress-induced rise in prolactin levels in the virgin animals was concurrent with an increase in prolactin receptor activation within the adrenal cortical cells. This adrenal response was not seen in either the stressed or control lactation group, an observation that may be in part explained by the observed downregulation of prolactin receptor mRNA expression within this tissue. Further evidence of suppression of the HPA axis during lactation was revealed using in situ hybridisation to demonstrate that while acute restraint stress increased corticotrophin releasing hormone (CRH) mRNA expression in the hypothalamic paraventricular nucleus in both virgin and lactating mice, the magnitude of this response was reduced in the latter group. This potentially adaptive response did not, however, appear to result from the altered prolactin profile during lactation because it was not affected by the pharmacological suppression of prolactin secretion from the pituitary. This study therefore suggests that during lactation the response of the HPA axis to stress is suppressed at multiple physiological levels which are mediated by both prolactin-dependent and prolactin-independent mechanisms.

Micromechanical modeling of devulcanized ground tyre rubber, graphene platelets, and carbon black in recycled natural rubber blends

AbstractWaste tyres are a global problem, with 1.5 billion being generated annually. To reduce this problem, a circular economy for tyres should be developed. This requires the incorporation of recycled tyre rubber in tyre products. Yet, most recycled rubber is of insufficient quality. Recycled rubber must react sufficiently well with virgin rubber to be elastically effective in the 3D crosslinked network. Although a broad range of devulcanization techniques have been developed, many recycled‐virgin rubber blends show significant reductions in stiffness compared with their virgin counterparts. This paper demonstrates that micromechanical models for filler reinforcement can be used to evaluate whether recycled rubber behaves in an elastically effective manner. Furthermore, mechanical devulcanization of ground tyre rubber (GTR) by solid‐state shear milling was shown to produce a recycled rubber powder that is elastically effective when blended with virgin natural rubber (vNR). These blends match the equivalent virgin rubber stiffness, despite high‐recyclate content (30/70 vNR/GTR). The addition of nanofillers (carbon black and graphene nanoplatelets) to these blends was evaluated to see how they compared with virgin compounds and filler reinforcement theories. This process may allow for incorporation of devulcanized rubber into existing products, promoting a circular economy for high‐value rubber recycling.

Possible handle for broadening the catalysis regime towards low temperatures: proof of concept and mechanistic studies with CO oxidation on surface modified Pd-TiO2.

The present work demonstrates the effect of temperature-dependent surface modification (SM) treatment and its influence in broadening the catalysis regime with Pd-TiO2 catalysts prepared by various methods. Due to SM induced changes, a shift in the onset of CO oxidation activity as well as broadening of the oxidation catalysis regime by 30 to 65 K to lower temperatures is observed compared to the temperature required for virgin counterparts. SM carried out at 523 K for PdPhoto-TiO2 exhibits the lowest onset (10% CO2 production - T10) and T100 for CO oxidation at 360 and 392 K, respectively, while its virgin counterpart shows T10 and T100 at 393 and 433 K, respectively. The SMd Pd-TiO2 catalysts were investigated using X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS) and atomic force microscopy (AFM). It is observed that diffusion of atomic oxygen into Pd-subsurfaces leads to SM and changes the nature of the surface significantly. These changes are demonstrated by work function (ϕ), surface potential, catalytic activity, and correlation among them. UPS results demonstrate the maximum increase in ϕ by 0.5 eV for PdPhoto-TiO2 after SM, compared to all other catalysts. XPS study shows a moderate to severe change in the oxidation states of Pd due to atomic oxygen diffusion into the subsurface layers of Pd. Kelvin probe force microscopy (KPFM) study also reveals corroborating evidence that the surface potential increases linearly with increasing temperature deployed for SM up to 523 K, followed by a marginal decrease at 573 K. The ϕ measured by KPFM and UPS shows a similar trend and correlates well with the changes in catalysis observed. Our results indicate that there is a strong correlation between surface physical and chemical properties, and ϕ changes could be considered as a global marker for chemical reactivity.

Glass fibre composites recycling using the fluidised bed: A study into the economic viability in the UK

<abstract> <p>As it stands, the UK has no commercialised process capable of recycling waste glass fibre reinforced thermosets, resulting in disposal via landfill or energy from waste facilities. Thermal recycling within a fluidised bed process has been demonstrated to successfully recover clean glass fibre from composite waste materials, such as wind turbine blades, and successfully reuse it as a reinforcement phase in second life composites. If brought to a commercial scale, this technology has the potential to divert up to 1200 kt of mixed glass fibre reinforced plastics (GRP) waste and an additional 240 kt of wind blade waste away from UK landfill sites over the next fifteen years, while offsetting the environmental impact and raw material consumption of virgin glass fibre production. Despite this, commercialisation and long-term success depend on economic viability and resilience of the recycling technology, ensuring that sufficient value is added to offset costs required to bring recyclate products to market. In this study, techno-economic analysis was used to analyse the economic outlook for at scale fluidised bed recycling plants within the context of the current and future UK glass fibre reinforced plastic waste landscape. It was found that fluidised bed recycling plants operating well within current UK waste volumes can maintain gate fees that are competitive with landfill while producing recycled glass fibre (rGF) at less than 50% of the prices of virgin counterparts. Plants processing single waste streams, such as wind blades, can maintain long term profitability despite irregular flow of waste feedstock availability. Despite higher transportation cost, total recycling costs are lower for national level plants. Therefore, it is recommended to accept composites from multiple waste streams to maximise operating capacity, profits and return on investment.</p> </abstract>

Recycled carbon fibers as an alternative reinforcement in UHMWPE composite. Circular economy within polymer tribology

The increasing demand of carbon fiber reinforced polymers over the last few decades has brought attention to critical aspects such as disposal, environmental impact, and cost of production. Therefore, adopting a circular economy approach focused on improving efficiency is an enticing alternative nowadays. This investigation is focused on the mechanical and tribological characterization of ultra high molecular weight polyethylene (UHMWPE) composites reinforced with virgin (vCF) and recycled carbon fibers (rCF) under water lubricated conditions. An improvement of 208% in Young’s modulus, 105% in ultimate tensile strength and 146% in hardness for the samples with 30%wt rCF, compared to pure UHMWPE, was observed. Reductions of up to 62% in coefficient of friction and 32% in wear rates for 10 wt% CF composites were obtained, facilitated through the formation of a transfer film, which was present on the countersurfaces. The results of this project show that the composites containing recycled fibers exhibit a comparable performance to their virgin counterparts. An economical evaluation estimated possible monetary savings of 910.2 M€ in a time span from 2022 to 2026 by using rCF in composite production, providing arguments for the use of rCF reducing the environmental impact and cost without compromising performance.

UV aging of microplastic polymers promotes their chemical transformation and byproduct formation upon chlorination

The presence and accumulation of microplastics (MPs) in water and wastewater is a growing concern. When released to the water bodies, microplastics can be subject to surface weathering due to ultraviolet (UV) exposure. In this study, the effects of UV aging of six MP polymers from three groups (e.g., polyamide, polyester, and polyolefin) on their chlorine reactivity, chemical transformation, and formation of disinfection byproducts (DBPs) were studied. Polyamide (e.g., polyamide 6) in both virgin and UV-aged forms showed significantly higher chlorine demands than other MP polymers (915.5–947.9 versus 7.0–21.1 μmol/g MP in 24 h), and polyolefins were relatively inert to chlorine. UV aging enhanced the destructions of functional groups of polyamide and polyester upon chlorination, promoting the chlorine demands and leaching of organics by up to 1.7- and 2.4-fold, respectively. Polymer monomer and oligomers of polyamide 6 and toxic or endocrine disrupting additives (e.g., dimethyl phthalate and butyl octyl phthalate) were identified in leachates from chlorinated MP polymers by mass spectrometry. Meanwhile, up to >10-fold increases in the yields of trihalomethane, haloacetic acid, haloacetaldehyde, haloacetonitrile, and haloacetamide were observed from 30-day UV-aged MP polymers as compared to their virgin counterparts. Overall, this study reveals that UV aging can promote the reactivity and chemical transformation of MP polymers during chlorination, especially for polyamide and polyester, increase the release of polymer monomers, oligomers, and additives, and aggravate the role of MP polymers as DBP precursors.

Nuts and bolts of tropical tuna purse seine nets recycling: A circular business model

Tropical tuna purse seiners are one of the most important contributors to end-of-life (EoL) fishing gears in the world, and these fishing nets can become a promising secondary raw material. Thus, tuna companies are looking for possibilities to valorize them by applying circular economy (CE). This contribution aims at assessing the viability of creating a circular business model out of recycled tropical tuna purse seine EoL nets. The yearly contribution of the Spanish tuna freezer purse seine companies to EoL fishing nets was estimated at 900 tons. Three pilot projects were implemented (involving 80 tons of EoL tuna nets) to learn about the monetary and material flows, supply chain, stakeholders' perception, and the environmental impacts of upcycling polyamide nets into four marketable products (i.e., conditioned fishing nets, backpacks, fishers' dungarees, and sunglasses). The results indicate that recycled regrinds/flakes and pellets were 37 and 50%, respectively, more expensive than virgin counterparts, but the yarn may achieve competitive production costs in the textile industry, with an additional environmental benefit close to 69% per kg of virgin–origin yarn. The challenges faced when recycling EoL polyamide fishing nets were discussed. Innovation and logistics appear to play a fundamental role in making the business sustainable. Besides, the circular business model methodology to assess the value proposition was also discussed in its empirical application.

Enhanced damping and stiffness trade-off of composite laminates interleaved with recycled carbon fiber and short virgin aramid fiber non-woven mats

This paper proposes composite laminates interleaved with recycled carbon fiber and short virgin aramid fiber non-woven mats to enhance the trade-off of mechanical damping and stiffness. Compared with their virgin counterparts, recovered carbon fibers (rCFs) have the potential for damping enhancement at the cost of only minimal degradation in strength. A papermaking method was used to convert rCFs and virgin aramid fibers (vAFs) separately into 60 g/m2 non-woven mats, which were then sandwiched between two layers of 125 g/m2 epoxy resin films before interleaving. A vacuum-assisted compression molding process was then used to produce the laminates. The effect of a titanate coupling agent on the adhesion between the mats and the epoxy matrix was studied. The experimental results showed that the titanate coupling agent was an effective sizing agent for rCF and vAF mats with epoxy matrix. The laminate with a single core layer of sized rCF mat showed better flexural properties and dynamic performance than those with the sized vAF mat. The flexural modulus and dynamic properties were found to depend on the stacking sequence of the added non-woven mats. Compared with the control sample, the best laminate had a figure of merit of 0.73 GPa, which was 23.7% higher.

Life Cycle Assessment of a Thermal Recycling Process as an Alternative to Existing CFRP and GFRP Composite Wastes Management Options.

There are forecasts for the exponential increase in the generation of carbon fibre-reinforced polymer (CFRP) and glass fibre-reinforced polymer (GFRP) composite wastes containing valuable carbon and glass fibres. The recent adoption of these composites in wind turbines and aeroplanes has increased the amount of end-of-life waste from these applications. By adequately closing the life cycle loop, these enormous volumes of waste can partly satisfy the global demand for their virgin counterparts. Therefore, there is a need to properly dispose these composite wastes, with material recovery being the final target, thanks to the strict EU regulations for promoting recycling and reusing as the highest priorities in waste disposal options. In addition, the hefty taxation has almost brought about an end to landfills. These government regulations towards properly recycling these composite wastes have changed the industries’ attitudes toward sustainable disposal approaches, and life cycle assessment (LCA) plays a vital role in this transition phase. This LCA study uses climate change results and fossil fuel consumptions to study the environmental impacts of a thermal recycling route to recycle and remanufacture CFRP and GFRP wastes into recycled rCFRP and rGFRP composites. Additionally, a comprehensive analysis was performed comparing with the traditional waste management options such as landfill, incineration with energy recovery and feedstock for cement kiln. Overall, the LCA results were favourable for CFRP wastes to be recycled using the thermal recycling route with lower environmental impacts. However, this contradicts GFRP wastes in which using them as feedstock in cement kiln production displayed more reduced environmental impacts than those thermally recycled to substitute virgin composite production.

Sustainable Polymers from Recycled Waste Plastics and Their Virgin Counterparts as Bitumen Modifiers: A Comprehensive Review.

The failure of bituminous pavements takes place due to heavy traffic loads and weather-related conditions, such as moisture, temperature, and UV radiation. To overcome or minimize such failures, a great effort has been put in recent years to enhance the material properties of bitumen, ultimately improving field performance and increasing the pavement service life. Polymer modification is considered one of the most suitable and by far the most popular approach. Elastomers, chemically functionalised thermoplastics and plastomers * (* Note: notwithstanding the fact that in Polymer Science the word ‘plastomer’ indicates a polymer with the simultaneous behaviour of an elastomer and plastics (thermoplastics), this paper uses the term ‘plastomer’ to indicate a thermoplastic polymer as it is more commonly found in Civil and Pavement Engineering.) are the most commonly used polymers for bitumen modification. Plastomers provide several advantages and are commonly acknowledged to improve high-temperature stiffness, although some of them are more prone to phase separation and consequent storage instability. Nowadays, due to the recent push for recycling, many road authorities are looking at the use of recycled plastics in roads. Hence, some of the available plastomers—in pellet, flakes, or powder form—are coming from materials recycling facilities rather than chemical companies. This review article describes the details of using plastomers as bitumen modifiers—with a specific focus on recycled plastics—and how these can potentially be used to enhance bitumen performance and the road durability. Chemical modifiers for improving the compatibility between plastomers and bitumen are also addressed in this review. Plastomers, either individual or in combination of two or three polymers, are found to offer great stiffness at high temperature. Different polymers including HDPE, LDPE, LLDPE, MDPE, PP, PS, PET, EMA, and EVA have been successfully employed for bitumen modification. However, each of them has its own merit and demerit as thoroughly discussed in the paper. The recent push in using recycled materials in roads has brought new light to the use of virgin and recycled plastomers for bitumen modification as a low-cost and somehow environmental beneficial solution for roads and pavements.

Synergy of Interlaminar Glass Fiber Hybridization on Mechanical and Dynamic Characteristics of Jute and Flax Fabric Reinforced Epoxy Composites

ABSTRACT Natural fiber composites (NFC) exhibit good specific mechanical properties in comparison to synthetic fiber composites (SFC). The study investigates interlaminar glass (G) fiber hybridized jute (J) and flax (F) reinforced epoxy composites designated as JGGJ, GJJG, FGGF, and GFFG along with their virgin counterparts. Composite laminates of four plies are manufactured by hand-layup followed by compression molding to investigate tensile, flexural, and interlaminar shear properties. Further the effect of hybridization is also investigated for modal frequencies and damping ratio obtained from experimental modal analysis. Glass fiber hybridization as extreme layers shows significant improvement in flexural and shear properties as compared to tensile. Glass fiber reinforcement, as core layers improve the damping by 155.55% and 101.31% for JGGJ and FGGF, respectively, over pure glass epoxy. However with increase in bending stiffness of GJJG and GFFG, the bending modal frequency is improved. Also, the modal frequency and damping ratio increases following a power-law variation with a decrease in the free length. Finite element and analytical validations are presented to the experimental frequencies and flexural modulus, respectively. These studied hybrid composites can serve as semi-structural members like interior trim panels in automotive applications that possess significant strength and dissipate in-service vibrations effectively.

A new method for assessing the recyclability of powders within Powder Bed Fusion process

Recycling metallic powders used in the additive manufacturing (AM) process is essential for reducing the process cost, manufacturing time, energy consumption, and metallic waste. In this paper, the focus is on pore formation in recycled powder particles of stainless steel 316L during the selective laser melting process. We have introduced the concept of optimizing the powder bed's printing area in order to see the extent of the affected powders during the 3D-printing process. X-ray Computed Tomography (XCT) is used to characterize the pores inside the particles. The results from image processing of the tomography (rendered in 3D format) indicate a broader pore size distribution and a higher pore density in recycled powders compared to their virgin counterparts. To elucidate on this, the Electron Dispersion spectroscopy (EDX) analysis and Synchrotron-based Hard X-ray Photoelectron Spectroscopy (HAXPES) were performed to reveal the chemical composition distribution across the pore area and bulk of the recycled powder particles. Higher concentrations of Fe, Cr, and Ni were recorded on the interior wall of the pore in recycled particles and higher Mn, S and Si concentrations were recorded in the outer layer around the pore area and on the surface of the recycled particle. The pore formation in recycled powder is attributed to out-diffusion of Mn, S and Si to the outer surface as a result of the incident laser heat during the AM process due to higher electron affinity of such metallic elements to oxygenation. HAXPES analysis shows a higher MnO concentration around the pore area which impedes the in-diffusion of other elements into the bulk and thereby helps to creates a void. The inside wall of the pore area (dendrites), has a higher concentration of Fe and Cr oxide. We believe the higher pore density in recycled powders is due, at least in part to composition redistribution, promoted by laser heat during the AM process. Nanoindentation analyses on both virgin and recycled powder particles shows a lower hardness and higher effective modulus in the recycled powder particles attributed to the higher porosity in recycled powders.