Search Results (107)

The incorporation of ground tire rubber (GTR) into elastomeric compounds offers a sustainable route for recycling end-of-life tires; however, its effect on the structure–property relationships governing mechanical and dielectric performance remains insufficiently understood. In this study, NR/SBR composites containing 0–50 phr of devulcanized GTR were prepared and characterized through Fourier-transform infrared spectroscopy (FTIR), swelling analysis, thermogravimetric analysis (TGA), mechanical testing, and broadband dielectric spectroscopy. FTIR and swelling results revealed enhanced matrix–GTR interaction at intermediate GTR loadings (10–20 phr), evidenced by an increased intensity of sulfur-related bands and reduced swelling degree, indicating partial chemical integration of the recycled phase into the elastomer network. Mechanical testing showed that increasing GTR content increased stiffness at high loadings, while tensile strength, elongation at break, and toughness progressively decreased due to interfacial debonding mechanisms. TGA demonstrated that the main degradation temperature of the NR/SBR matrix remained essentially unchanged (418–425 °C) across all formulations, confirming preservation of thermal stability despite increasing structural heterogeneity. Dielectric spectroscopy (10⁻²–3 × 10⁶ Hz, 40–120 °C) revealed pronounced Maxwell–Wagner–Sillars interfacial polarization and thermally activated charge transport, with conductivity increasing with GTR content without evidence of electrical percolation, even at 50 phr. The results demonstrate that the performance of NR/SBR/GTR/SiO₂ composites is primarily controlled by the interfacial structure generated by the recycled phase. Intermediate GTR contents (10–20 phr) provide the most effective matrix–GTR interaction, while higher loadings mainly affect mechanical integrity and dielectric response through increased structural heterogeneity. These findings provide practical guidelines for designing sustainable elastomeric compounds with high recycled content while maintaining thermal stability and controlled electrical insulation properties. Full article

In response to the bottleneck issue of natural rubber selection in aircraft tire formulation design, this study proposes a data-driven screening methodology that integrates a simulated performance database with grey system theory. A multidimensional performance simulation database was constructed, encompassing representative NR brands from six major global producing regions: Malaysia, Indonesia, Thailand, Vietnam, Hainan (China), and Yunnan (China). This repository encompasses critical metrics, including raw rubber constitution, molecular characteristics, and the static/dynamic mechanical behaviors of vulcanizates. Utilizing this foundation, a novel material selection protocol was formulated, grounded in a multi-objective weighted intelligent grey target decision framework. The Analytic Hierarchy Process (AHP) was applied to ascertain differentiated performance criteria and assign corresponding weights, specifically tailored to the functional necessities of distinct aircraft tire sections. To substantiate the model’s efficacy, the primary tire of the ubiquitous Boeing 737-800 served as a validation case. The optimal Natural Rubber (NR) grade identified by the algorithm was cross-referenced with the empirical expertise and engineering practices of premier global tire manufacturers, thereby confirming the framework’s robustness and predictive accuracy. Consequently, this investigation establishes a comprehensive intelligent decision-making architecture, spanning data construction to engineering deployment, offering a quantitative and referential pathway for NR material screening in aviation applications. Full article

Waste tire disposal and high-ground-stress soft rock roadway instability are pressing global challenges. This study develops sustainable rubber granule concrete (RGC) using waste tire rubber as a key component, aiming to realize waste valorization and floor heave control. RGC’s mechanical properties (uniaxial/triaxial compression, compressibility, ductility) were systematically tested, and its pressure relief mechanism was validated via finite element analysis (ABAQUS/FLAC) and 60-day field monitoring. Results show that RGC with optimal parameters (12% rubber content, 3–4 GPa elastic modulus, 250–350 mm thickness) achieves 64% bottom stress reduction and >40% displacement control. The material’s excellent energy absorption and flexibility address the brittleness of conventional concrete, ensuring stable support in high-stress environments. This work provides a sustainable, cost-effective concrete modification strategy, bridging waste recycling and geotechnical engineering, with broad implications for low-intensity, high-toughness material applications. Full article

This study evaluated the partial and total replacement of zinc oxide (ZnO) with magnesium oxide (MgO) in styrene–butadiene rubber (SBR) composites, as well as the incorporation of ground tire rubber (GTR), aiming to develop more sustainable elastomer formulations. Ten formulations were prepared with varying ZnO/MgO ratios (100/0 to 0/100), with and without 20 phr of GTR. The composites were characterized by particle size distribution, morphology, rheometric behavior, density, crosslink density, mechanical properties, abrasion resistance, compression behavior, and thermo-oxidative aging. The results showed that hybrid ZnO/MgO activation systems exhibited a synergistic effect, enhancing vulcanization kinetics and mechanical performance compared to single-activator systems. Total replacement of ZnO by MgO was less effective, leading to reduced crosslink density and inferior properties. The addition of GTR increased compound viscosity and altered morphology but improved abrasion and compression resistance without significantly affecting tensile strength. Aging tests indicated good thermal stability, with maintenance or improvement of tensile properties due to post-curing effects. Overall, the combination of reduced ZnO content with MgO and GTR represents a viable approach for producing SBR composites with adequate performance and lower environmental impact. Full article

This research aims to study the compressive behavior of concrete with partial replacement of fine aggregate by recycled rubber. In addition, the mechanical capacity of these concretes will be analyzed when reinforced by carbon fibers (CFRP) and basalt (BFRP) confinement. To carry out the work, 48 cylindrical test specimens were made, corresponding to 4 mixes, with different percentages of recycled rubber by volume (0%, 10%, 20%, and 30%). The compressive behavior of unreinforced concrete with and without recycled rubber, reinforced concrete made from concrete with and without recycled rubber previously taken to failure, and reinforced concrete with and without recycled rubber without prior failure were evaluated in order to assess the influence of concrete quality before placing the reinforcement. The results show that replacing fine aggregate with recycled rubber in concrete reduces its strength and stiffness, increasing its ductility, with the optimum replacement percentage being 10%. On the other hand, confining concrete with FRP (BFRP and CFRP) improves its strength and ductility compared to unconfined concrete, obtaining similar values regardless of the initial strength of the reinforcing concrete. Confining concrete with CFRP achieves strength improvements of 26% compared to reinforcement with BFRP. Full article

Ground tire rubber (GTR) is composed of high-quality components; therefore, searching for new technologies for GTR recycling and upcycling is fully justified. In this work, the effect of micronized ground tire rubber content on the rheological, mechanical, thermal, and morphological properties, electrical conductivity, and electrochemical behavior of thermoplastic polyurethane/carbon black was investigated. The application of micronized ground tire rubber in the range of 5–20 wt% reduces the manufacturing cost by 5.6–22.6% and improves the electrical conductivity and electrochemical properties of composites. The results showed that higher contents of ground tire rubber increased the electrical conductivity of the studied materials from 11.7 to 33.8 S/m. This phenomenon is due to two factors: (i) additional carbon black present in GTR and (ii) phase separation that promotes local carbon-rich domains and facilitates conductive pathway formation. Electrochemical analysis revealed that the studied composites after laser activation can be used as flexible sensors. This research work confirms that using a ground tire rubber as a low-cost and valuable source of raw materials is a promising approach for the sustainable development of soft electronics. Full article

Aircraft functions under extreme environmental circumstances, encompassing both elevated and diminished temperatures, influence the material characteristics and inflation pressure of aircraft tires. This results in modifications to the tire’s cornering, affecting the shock absorption efficacy of the landing gear and maneuvering stability during cornering. This study examines the cornering characteristics of aircraft tires at four ambient temperatures: −60 °C, −40 °C, 25 °C, and 50 °C. The analysis of stress–strain findings of rubber materials at varying temperatures assessed the impact of ambient temperature on rubber properties. Based on this, a numerical model for tire cornering was constructed using ABAQUS to examine the impact of ambient temperature on the tire’s cornering characteristics. The model considers the intricate friction dynamics between the tire and road surface and the convergence tolerance parameter of ABAQUS. The precision of this model and methodology was confirmed through experimental testing. The findings demonstrate that ambient temperature significantly affects the lateral force and self-aligning torque of aircraft tires, hence impacting cornering stiffness considerably. The influence of radial force and rolling speed on cornering differs with varying ambient temperatures. These results offer significant insights into the design of aircraft tire environmental adaptability and aircraft ground handling systems. Full article

This study investigates the substitution of calcium carbonate (CaCO₃) with ground tire rubber (GTR) in EPDM-based elastomer formulations as a strategy for sustainable material development. Unlike conventional approaches, this work employs GTR as a direct filler replacement. Temperature scanning stress relaxation (TSSR) analyses confirm that GTR participates in vulcanization. Initial incorporation of GTR reduces crosslink density (CLD) and mechanical performance due to structural defects, while accelerators present in the recycled phase promote faster curing. This study focuses on the aging behavior of the compounds to evaluate possible long-term effects on the material. The thermo-oxidative stress leads to further crosslinking, resulting in higher CLD, increased stiffness and reduced elongation at break. Overall, partial replacement of CaCO₃ by GTR proves feasible, offering a balanced compromise between sustainability and performance, whereas high GTR contents significantly impair mechanical properties. Full article

Currently, large amounts of aggregate waste from the construction industry and ground tire rubber from the automotive sector are being generated. Enhancing and expanding recycling options for these materials is essential to support the transition toward a circular economy in both industries. This study proposes the use of recycled materials in the development of a seismic isolator designed for building partitions. As such, the new element must meet the performance requirements applicable to all materials used in building enclosures. Polyurethane is employed as a binder for the recycled components. The composite material is produced by combining polyurethane with varying proportions of recycled ground tire rubber and aggregates, expressed as a percentage of the polyurethane mass. The polyurethane is directly mixed with the recycled constituents. The resulting samples are subjected to thermal and acoustic testing to evaluate their suitability for partitions and enclosures in building construction in accordance with regulations. The results of the three tests indicate improvements in the measured properties, with the magnitude of enhancement depending on the ratio of ground tire rubber to aggregate. Overall, the developed composite materials exhibit characteristics and behavior compatible with the intended application. Full article

Scrap tire-derived geomaterial has been gaining attention recently as an alternative material for improving the ground. This paper presents a fundamental experimental investigation into sand–rubber mixtures using hollow cylinder torsional shear apparatus, with the aim of enhancing our understanding of the integrated effects of rubber content and cyclic stress ratio (CSR) on the liquefaction characteristics of the mixtures. The results show that the incorporation of granular rubber into sand not only reduces excess pore water pressure during cyclic loading but also alters the generation mode of pore water pressure. The liquefaction resistance of the sand–rubber mixture increases significantly when the rubber gravimetric proportion exceeds 10%. The energy dissipation per loading cycle decreases with increasing rubber content, whereas the cumulative dissipative energy exhibits an opposite trend, showing a positive correlation with rubber content. In addition, this rubber-enhanced effect shows CSR dependence; the cumulative energy dissipation significantly diminishes at a high CSR. Therefore, the effect of granular rubber addition to sand on pore water pressure tends to become more pronounced at higher rubber contents. Full article

Traditional approaches to overcoming energy loss from resistances of vehicular transit velocities have focused primarily on reducing aerodynamic drag through streamlining air flow. These approaches have overlooked significant reductions in resistance on highways by reducing rolling losses and the aerodynamic drag associated with boundary layer separation and leading-edge stagnation regions. Ground effect vehicles are able to make significant strides towards reducing these two resistances. These vehicles can approach an 80% reduction in resistance compared to conventional frame streamlining alone. These substantial reductions to resistance enable a more effective and broader range of electric vehicles, including electric trucks and railcars. Lower resistance enables higher speeds at the same power consumption. Examples of digital prototype performances include up to 50% and 30% reductions in resistance through mitigating rolling/drivetrain and boundary layer separation losses, respectively. Digital prototypes are able to reach a lift-to-drag efficiency of 25 while maintaining a 0.2 aspect ratio. A cascade of additional advantages arises from aerodynamic lift-enabling rubber tires on steel rails for multimodal and widespread service. This paper details the mechanisms of how to achieve substantial reductions in energy consumption and enable transit transformations. The technology enables open-ended evolution with far greater possibilities than current transit options. The technological evolution includes electric automobiles, delivery trucks, semi-trucks, and railcars using batteries and solar sheets with significant competitive advantages over fossil fuels. Full article

This study investigates additive-free cold calendering of ELT-derived rubber powders across three particle size fractions (<0.5 mm, 0.5–0.71 mm, and 0.71–0.90 mm) using a two-roll mill without external heating or virgin polymers, aiming to obtain a cohesive material. Results demonstrate particle size effects on material properties. The finest fraction exhibited the highest crosslink density (5.30 × 10⁻⁴ mol·cm⁻³), approximately 18% greater than coarser fractions, correlating with superior hardness (≈65 ShA) and elastic modulus (≈7.5 MPa). Tensile properties ranged from 1.6–1.8 MPa stress and 60–75% elongation at break, positioning calendered sheets between low-temperature compression-molded GTR and high-pressure sintered materials reported in the literature. The cold calendering process achieves competitive mechanical performance with reduced energy consumption, simplified processing, and complete retention of recycled content. These findings support the development of regulation-compliant ELT recycling technologies, with potential applications in nonstructural construction panels, vibration-damping components, and protective barriers, advancing circular economy objectives while addressing emerging microplastic concerns. Full article

End-of-life tires (ELTs) are an important source of energy and materials, with ELT powder (ELTp) being a secondary raw material of increasing industrial interest. However, the complex structure and composition of ELTp rubber pose technological difficulties and scientific challenges in some high-performance applications in the rubber industry. The mechanical recycling of ELTp produces ground tire rubber (GTR) powder, which is used, among other applications in the rubber field, to prepare thermoplastic vulcanizates (TPVs) due to the interest in these materials in the automotive and construction sectors. Over the last few decades, different approaches have been explored to minimize the limitations of these TPVs, including their large particle size and poor compatibility with GTR powder in other polymer matrices. This study applies different recycling procedures to GTR powder, based on thermal, chemical and mechanical methods, and combinations thereof, to minimize interfacial issues with other matrices used in TPV preparation. The effect of the different rubber recycling processes on the performance of the resulting TPVs was evaluated, optimizing the fraction of recycled rubber from ELTp and the vulcanization system to enhance the mechanical properties and obtain industrially competitive products. Full article

In this paper, the evaluation of the mechanical performance of novel, designed topologically optimized shin pads with advanced materials will be conducted with the aid of Finite Element Analysis (FEA) to assess the endurance of the final structure on impact phenomena extracted from actual real-life data acquired from contact sports. The main focus of the developed prototype is to have high-enough energy absorption capabilities and vibration isolation properties, crucial for the development of trustworthy protective equipment. The insertion of advanced materials with controlled weight fractions and lattice geometries aims to strategically improve those properties and provide tailored characteristics similar to the actual human skeleton. The final design is expected to be used as standalone protective equipment for athletes or as a protective shield for the development of human lower limb prosthetics. In this context, computational investigation of the dynamic mechanical response was conducted by replicating a real-life phenomenon of the impact during a contact sport in a median condition of a stud kick impact and an extreme case scenario to assess the dynamic response under shock-absorption conditions and the final design’s structural integrity by taking into consideration the injury prevention capabilities. The results demonstrate that the proposed lattice geometries positively influence the injury prevention capabilities by converting a severe injury to light one, especially in the gyroid structure where the prototype presented a unified pattern of stress distribution and a higher reduction in the transmitted force. The incorporation of the PA-12 matrix reinforced with the reused ground tire rubber results in a structure with high enough overall strength and crucial modifications on the absorption and damping capabilities vital for the integrity under dynamic conditions. Full article

The development of prosthetic limbs has benefited individuals who suffered amputations due to accidents or medical conditions. During the development of conventional prosthetics, several challenges have been observed regarding the functional limitations, the restricted degrees of freedom compared to an actual human limb, and the biocompatibility issues between the surface of the prosthetic limb and the human tissue or skin. These issues could result in mobility impairments due to failed mimicry of the actual stress distribution, causing discomfort, chronic pain, and tissue damage or possible infections. Especially in cases where underlying conditions exist, such as diabetes, possible trauma, or vascular disease, a failed adaptation of the prosthetic limb could lead to complete abandonment of the prosthetic part. To address these challenges, the insertion of topologically optimized parts with a biomimetic approach has allowed the optimization of the mimicry of the complex functionality behavior of the natural body parts, allowing the development of lightweight efficient anthropomorphic structures. This approach results in unified stress distribution, minimizing the practical limitations while also adding an aesthetic that aids in reducing any possible symptoms related to social anxiety and impaired social functioning. In this paper, the development of a novel anthropomorphic designed prosthetic foot with a novel Thermoplastic Polyurethane-based composite (TPU-Ground Tire Rubber 10 wt.%) was studied. The final designs contain advanced sustainable polymeric materials, gyroid lattice geometries, and Finite Element Analysis (FEA) for performance optimization. Initially, a static evaluation was conducted to replicate the phenomena at the standing process of a conventional replicated above-knee prosthetic. Furthermore, dynamic testing was conducted to assess the mechanical responses to high-intensity exercises (e.g., sprinting, jumping). The evaluation of the dynamic mechanical response of the prosthetic limb was compared to actual plantogram-derived foot pressure data during static phases (standing, light walking) and dynamic phenomena (sprinting, jumping) to address the optimal geometry and density, ensuring maximum compatibility. This innovative approach allows the development of tailored prosthetic limbs with optimal replication of the human motion patterns, resulting in improved patient outcomes and higher success rates. The proposed design presented hysteretic damping factor and energy absorption efficiency adequate for load handling of intense exercises (0.18 loss factor, 57% energy absorption efficiency) meaning that it is suitable for further research and possible upcycling. Full article