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This study investigates the valorization of two industrial waste streams - nitrile butadiene rubber (NBR) scraps and electric arc furnace (EAF) slag – in the development of recycled NBR compounds filled with EAF slag as filler. A new recycling method for NBR scraps is employed via calendering at room temperature without the need for curatives, chemical agents, or pre-grinding. The resulting recycled NBR is then used as a matrix for EAF slag particles to produce sustainable rubber compounds that are entirely recycled. Characterization reveals that incorporating EAF slag enhances the devulcanization process of recycled NBR during recycling. The filler grain size affects composite properties like hardness, crosslink density, and tensile modulus, with finer slag particles (

Carbon black (CB) is the most widely used reinforcing filler for rubber. Nowadays there are several concerns regarding this traditional petroleum-based filler: on one side its environmental footprint is enormous and its production process is no more sustainable and on the other side its price increases annually. For these reasons, sustainable alternative fillers are being studied. In the present research the main waste of the steel industry, namely the steel slag from electric arc furnace (EAF), is investigated as non-conventional filler for a nitrile butadiene rubber matrix (NBR). The slag has been characterized to ensure its safe reuse as filler according to the heavy metals leaching. The slag filled compounds have been characterized and compared to CB filled compounds, in terms of processability by rheometric parameters, mechanical properties, Payne effect, and physicochemical properties to investigate the filler-matrix interaction. From the obtained results, it was shown that EAF slag-filled NBRs are comparable to CB filled NBRs in terms of crosslink kinetics and, when compared at the same hardness level, are comparable in terms of viscosity, stiffness, and elongation at break, while when compared at the same filler volume fraction are similar in terms of compression set and stress relaxation.

Joining is a key part of the manufacturing process including automobile, household appliances, aircraft manufacture, and medical sectors. Vibration welding (VW), also known as linear friction welding, is the most used technique to join thermoplastic components and composites mostly due to its simplicity, controllability, versatility of applications, and cost-effectiveness in terms of thermal efficiency, compared to conventional adhesive, mechanical fastening, and other fusion bonding techniques. This review aims to provide a comprehensive overview of the recent advances in understanding the multiple factors affecting vibration weld strength of thermoplastic polymers and their composites. The key process parameters such as weld pressure, frequency, amplitude and time are discussed along with their influence on weld strength of various materials. The effects of material characteristics like crystallinity, fiber reinforcement, and nanoparticles are summarized. Furthermore, the impact of joint design factors like thickness and geometry on mechanical performance is reviewed. The current challenges and future research directions for optimizing vibration weld strength through process, material, and design selections are highlighted. The overall goal is to present updated understanding on achieving strong vibration welded joints by considering the complex interplay between processing, structure, and properties.

Over the years, natural resources conservation and waste management have become increasingly important globally, leading to the promotion of systemic approaches that integrate different processes by sharing materials, energy, and services. Recycling and reuse of materials have also become an area of increasing interest. This study investigates the potential use of ladle furnace (LF) slag, a waste product of the steel industry, as a non-conventional filler for rubber compounds. LF slag is produced during the refinement stage of the steelmaking process and is almost entirely landfilled. This research compares a standard nitrile-butadiene rubber (NBR) filled with calcium carbonate to an NBR filled with 10% LF slag (by volume). The study evaluates the compounds' processability and mechanical performance by means of rheometer analysis, hardness test, tensile test, compression test, and compression set. The use of LF slag in NBR rubber compounds could represent an example of a circular economy, where waste from one industry becomes a raw material for another.

Reinforcement of polymers by the addition of particles filler is a complex phenomenon that depends mainly on the hydrodynamic effect and a complex interplay between polymer, filler, and interfacial region. Mineral fillers are usually adopted as low-cost extenders due to their lower cost.In this study, the influence of a waste material such as electric arc furnace steel slag is assessed as filler for Nitrile-Butadiene Rubber following experimental procedures and analytical calculations adopted for traditional fillers. It was found that the slag content affects the static and the dynamic properties by increasing the material's capability to storage and dissipate energy. In addition to an important contribution of the hydrodynamic effect, the presence of an increasing immobilized rubber fraction around the slag particles (quantified by a differential scanning calorimetry analysis) plays a central role. The slag stiffens the NBR composite; the increase of static tensile and dynamic shear storage moduli was found to be consistent with the Halpin-Tsai and Guth-Gold prevision models respectively. Moreover, the non-linear dynamic behavior was found to be well-fitted by the Kraus equation models. The reinforcing ability of the slag particles as filler was confirmed by the negative slope of the Kraus plot on swelling data.

Conductive nanocomposites play a significant role in tissue engineering by providing a platform to support cell growth, tissue regeneration, and electrical stimulation. In the present study, a set of electroconductive nanocomposite hydrogels based on gelatin (G), chitosan (CH), and conductive carbon black (CB) was synthesized with the aim of developing novel biomaterials for tissue regeneration application. The incorporation of conductive carbon black (10, 15 and 20 wt.%) significantly improved electrical conductivity and enhanced mechanical properties with the increased CB content. We employed an oversimplified unidirectional freezing technique to impart anisotropic morphology with interconnected porous architecture. An investigation into whether any anisotropic morphology affects the mechanical properties of hydrogel was conducted by performing compression and cyclic compression tests in each direction parallel and perpendicular to macroporous channels. Interestingly, the nanocomposite with 10% CB produced both anisotropic morphology and mechanical properties, whereas anisotropic pore morphology diminished at higher CB concentrations (15 and 20%), imparting a denser texture. Collectively, the nanocomposite hydrogels showed great structural stability as well as good mechanical stability and reversibility. Under repeated compressive cyclic at 50% deformation, the nanocomposite hydrogels showed preconditioning, characteristic hysteresis, nonlinear elasticity, and toughness. Overall, the collective mechanical behavior resembled the mechanics of soft tissues. The electrical impedance associated with the hydrogels was studied in terms of the magnitude and phase angle in dry and wet conditions. The electrical properties of the nanocomposite hydrogels conducted in wet conditions, which is more physiologically relevant, showed a decreasing magnitude with increased CB concentrations, with a resistive-like behavior in the range 1 kHz–1 MHz and a capacitive-like behavior for frequencies 1 MHz. Overall, the impedance of the nanocomposite hydrogels decreased with increased CB concentrations. Together, these nanocomposite hydrogels are compositionally, morphologically, mechanically, and electrically similar to native ECMs of many tissues. These gelatin-chitosan–carbon black nanocomposite hydrogels show great promise for use as conducting substrates for the growth of electro-responsive cells in tissue engineering.

The European steel industry produces about 70 million tons/year of steel by the electric arc furnace (EAF). The slag consists of about 15% by weight of the produced steel, thus from the perspective of the circular economy, it has a high potential as a co-product. This research aims to assess an innovative reuse of EAF slag as filler in different polymer matrixes: thermoplastic (polypropylene), thermosetting (epoxy resin), elastomeric (nitrile butadiene rubber), and recycled end of life rubber tire. A comparison between neat polymer and polymer filled with a certain amount of EAF slag has been carried out by tensile (or flexural), compression, and hardness tests. Experimental results show that slag as a filler increases the composites’ hardness and elastic modulus at the expense of toughness. For a safe reuse of the slag, the leaching of hazardous elements must comply with current legislation. It was found that, although the used EAF slag releases small amounts of Cr, Mo, and V, incorporating it into a polymer matrix reduces the leaching. The EAF slag particles distribution has been observed by scanning electron microscopy (SEM) images. The obtained results show good technical feasibility of this innovative slag application so that it could pave the way to a new industrial symbiosis between dissimilar sectors, bringing economic and environmental benefits.

This work reports and analyzes the mechanical properties of some composites obtained using stabilized waste with epoxy resins E-227. For comparison, correspondent composite samples were realized using calcite as a filler. The recovered stabilized waste was obtained by means of a new method to stabilize municipal solid waste incineration (MSWI) fly ash (FA), based on the use of bottom ash (BA). The aim of this paper is to show that the stabilization process, which can be considered a zero—waste treatment, produces inert materials, that can be reused as a filler. The production of new filler was made on a pilot plant, designed to verify the transferability of the proposed stabilization technology. Mechanical analysis revealed that flexural modulus raises by increasing the filler content around 30% wt, independently of filler type, stabilized sample or calcium carbonate. Mechanical properties are lower in the samples with the high amount of filler due to the crowding effect. The morphology of composite materials showed a non-homogeneous dispersion of particles in stabilized sample filler, characterized by large particle agglomerates. Finally, according to the ESCAPE simplified method, the obtained composites result more sustainable in comparison with the corresponding ones produced by using natural resources (like calcite). These findings open new possibilities for the reuse of the stabilized material, in frame of circular economy principles, with environmental and economic advantages.