End-of-life Tires Research Articles

Reuse of end-of-life tires and their impact on the setting time of mortars: Experimental study using a new measuring equipment

End-of-Life Tires (ELT) have posed severe environmental problems for the European Union due to their slow degradation and the difficulties in recycling elastomers such as rubber. For this reason, its reincorporation into the manufacturing process of new sustainable construction materials has become an increasingly viable alternative. In this research, an experimental campaign is carried out to understand better the setting process of masonry mortars with the incorporation of ELT as a partial replacement for aggregates. To do this, a new measuring device has been developed that allows real-time monitoring of the setting process in mortars. The proprietary design equipment acquired for this research combines Arduino technology with capacitive measurement equipment. The results show how it is possible to determine in real-time the evolution of the setting of masonry mortars regardless of the type of aggregate used in its manufacture. In turn, physical and mechanical characterization of the elaborated mortars has been carried out, studying the evolution of these properties over time. It can be seen how the incorporation of ELT s reduces the mechanical resistance of the mortars but improves their dimensional stability by reducing shrinkage during setting, which is of particular interest in mortars made with recycled aggregate, specially designed for the production of prefabricated construction elements.

CFD simulation of a shell and multiple tubes condensing heat exchanger in a modified microwave plant applied for reprocessing End of Life Tires (ELTs)

AbstractThe condensation heat exchanger has a critical role in the microwave reduction process to separate and capture valuable by‐products after the microwave reactor. This study aims to perform a computational fluid dynamics (CFD) simulation of a condenser to assess the heat transfer performance of the heat exchanger comprehensively. The type of heat exchanger used for this study is based upon an existing industrial‐scale condenser taken from a conventional thermal pyrolysis end of tires (ELT) reprocessing plant and repurposed for integration into a 1500 kg/h ELT microwave reduction process. The condenser is a shell‐and‐multiple‐tube heat exchanger in which the syngas passes through the tubes while cold water from a cooling tower is placed inside the shell. After the simulation, the effects of inlet temperatures and mass flow rates of the gas and water are investigated. The results show that the heat transfer rate is 58 kW for the inlet air velocity of 0.25 m/s and increases due to the convective heat transfer by 32% and 55% when the air velocity rises to 0.5 and 1 m/s, respectively, for the inlet gas and water temperatures of 80 and 15°C, respectively. Additionally, because the outlet air temperature and the inlet water temperature are strongly correlated with convective heat transfer, the outlet air temperature is equivalent to 17.2, 22.3, and 29.5°C when the inlet water temperature is 15, 20, and 25°C, respectively.

Consecutive recovery of recovered carbon black and limonene from waste tyres by thermal pyrolysis in a rotary kiln

End of life tyres are one of the most abundant and least recycled waste streams. Material recovery processes that accommodate for the complexity and heterogeneity of waste tyres, such as pyrolysis, require urgent development. Examples of recycled tyre pyrolysis products include recovered carbon black (RCb), a recycled filler, and limonene, a solvent, although investigations reporting the recovery of both are limited. In this study the pyrolysis of waste tyres was investigated in a batch rotary kiln under varying conditions (temperature, gas flow, sample mass). Characterisation analysis was then applied to selected samples of RCb (BET surface area, transmissibility of toluene extract, proximate analysis) and tyre pyrolysis oil (yield, limonene content, FTIR). The best RCb (77.7 m2/g, 0.2% volatile matter, 17.0% ash, 94.8% transmissibility of toluene extract) was produced at 550 °C with a high ratio of purge gas flow (2000 mL/min) to rubber sample mass pyrolysed (100 g), minimising the recondensation of tarry volatiles on the RCb. The highest oil and limonene yield (38.4% and 17.4 g/kg waste tyres respectively) was produced at a temperature of 550 °C with a low ratio of purge gas (400 mL/min) to rubber sample pyrolysed (200 g), as these conditions prevented the decomposition of limonene to less valuable products and improved the oil trap condensation efficiency. These findings demonstrate the importance of pyrolysis processing conditions when considering the consecutive production of RCb and solvents from waste tyre pyrolysis, which shows significant future potential to valorise waste tyres, incentivising recycling.

Experimental investigation on mechanical properties of HSSCC containing waste steel fibers obtained from end-of-life tires

In this study, use of end-of-life tires (ELTs) in self-consolidating concretes (SCC), which enable higher rates of fiber use than conventional concrete due to its superior flow properties, for the elimination of the environmental negative impacts and recycling of them were aimed. Besides, it is aimed to investigate the behavior of waste steel wires with different aspect ratio obtained from different types of tires, contrary to what is mostly researched in the literature. Therefore, bead, cord and base wires, obtained from tires, were used in high-strength self-consolidating concrete (HSSCC) production as fiber reinforcement. Fresh and hardened state properties of the waste wire-reinforced (1-2-3%) samples of different sizes that were produced, were compared with industrial steel-reinforced and non-fibrous samples. In this regard, slump flow and T50 durations were determined, compression and bending tests were performed. Significant improvements in the mechanical properties of conventional concretes were observed with the use of waste wire. Using the optimum ratio of waste wire, an increase of approximately 102% in flexural strength and 14% in compressive strength was observed compared to the reference specimen. Aspect ratio was recognized as one of the most effective factor on optimum fiber content. Moreover, experimental results were analyzed with "paired sample t-test", and it was seen that there were no considerable differences in the mechanical properties of the samples in which industrial fiber and waste-wire had been used. Besides, cost analysis was carried out to assess the economic benefits of the use of waste tire wires in the concrete industry.

Effect of Use Sugarcane Bagasse Ash and Rubber Tyre as A Partial Replacement of Cement and Coarse Aggregate in Concrete

Abstract: Recycling and usage of waste products can be a viable option in the waste management of many materials. The present study focuses on the utilization of Sugarcane Bagasse Ash(SCBA) as replacement material for cement and rubber tyre as replacement material for coarse aggregate in concrete production. Noting the increasing volumes and difficulty in the disposal of wastes from rubber tyres and SCBA, this paper discusses test results of use of SCBA and recycled tyres in concrete for possible application in the construction industry. Sugarcane Bagasse ash contains high amorphous silica content and aluminium ion. For experimental investigations, Sugarcane bagasse ash and its chemical properties are obtained from Sakthi sugars private ltd, Aapakoodal, Tamilnadu. Ordinary Portland cement was partly replaced by sugarcane bagasse ash in the ratio of 0%, 10%, 20% and 30% by weight. The results indicate that inclusion of Sugarcane Bagasse Ash in concrete up to 20% level significantly enhanced the strength of concrete. In 2008, around one billion end-of-life tyres (ELTs) were being produced globally each year. As a possible means of disposing the tyres, it is proposed to use rubber tyres as coarse aggregate in concrete. Tyres cut into pieces with maximum size of 20 mm to use as coarse aggregate.It were used in the replacement of 15% of the normal gravel. Grade of concrete used in this paper is M30.Compressive strength, splitting tensile, and flexural strength tests were conducted according to the various BS codes. This paper also demonstrated the variation in the compressive strength of the non-conventional concrete when the BS and ACI methods are used in the design of the mix.

Release of PAH from Secondary Products Made from End-of-Life Tire Recyclates into 20% Aqueous Ethanol as Assessment of Human Dermal Absorption

Compliance with the legal limits set at the European level for the content of polycyclic aromatic hydrocarbons (PAH), which are harmful to human health and the environment, is of central importance for the recycling of rubber, particularly end-of-life tires (ELT), into secondary products, e.g., elastic fall protection mats or anti-slip mats for the transport sector. However, different regulations associated with different analytical methods apply to newly produced tires on the one hand and secondary products made from ELT on the other. Given these discrepancies, ELT can potentially contain levels of PAH, which can be problematic when reused in consumer products. The total PAH content, however, is not without doubt a reliable risk indicator, which should ultimately be based primarily on the transfer of the substances from the product into the skin of human beings or their release into the environment. Accordingly, additional studies are required to determine the extent to which migration-based measurements are more suitable for risk assessment and how the PAH content correlates with migration. Complementing the recently published results of PAH content in different types of ELT, this study investigates the release of PAH for a range of typical secondary materials composed entirely or partly of ELT. In the present study, migration tests with 20% aqueous ethanol were applied, a methodology that has been shown in previous investigations by others to reflect human skin exposure well, and the resulting migration rates of PAH are determined.

Thermal decomposition characteristics of the tire pyrolysis oil derived from a twin-auger reactor: Study of kinetics and evolved gases

This study presents the characterization of the thermal decomposition (oxidation and pyrolysis) behavior of the oil (TPO) derived from the pyrolysis of End-of-Life Tires (ELT) in a twin-auger pyrolyzer, by means of thermogravimetric and calorimetric analyses, coupled with Fourier transform infrared spectroscopy (TG–FTIR). TPO oxidation and pyrolysis were conducted using air and N2, respectively, at three different heating rates (5, 10, and 20 °C/min) in a temperature range between 30 and 700 °C. Along the temperature program, the evolved gases were directed to the FTIR cell, where the functional groups within species present were measured. A global kinetic analysis was performed for the TPO oxidation, using four isoconversional methods, as well as the distributed activation energy model (DAEM) developed by Miura and Maki. The results obtained suggest that the oxidation process of TPO can be divided into three different reaction stages, namely: low-temperature oxidation (LTO) (<400 °C), fuel decomposition (400–500 °C), and high-temperature oxidation (HTO) (500–700 °C). Within the LTO stage, oxygen addition reaction to produce hydroperoxides were considered dominant in the initial stages, while the decomposition of the formed hydroperoxides was more significant at the later stage. Due to the characteristics of TPO, e.g., the presence of highly volatile compounds, the evaporation of hydrocarbons played an important role within the LTO stage. In the fuel decomposition stage, the formation of coke by the oxidative cracking of LTO residue and oxygen addition were believed to be the main reactions leading to gaseous products such as CO, CO2, H2O. Finally, in the HTO stage, the oxidation of coke was considered as the main reaction, exhibiting an evident exothermic activity. The activation energy distribution shows a similar pattern among the isoconversional methods and DAEM, with fluctuations between 40 and 200 kJ/mol. The analysis presented in this work sheds new light on the thermal decomposition of oil derived from the pyrolysis of ELT, which is relevant for its use in combustion systems.

Performance of prototype seismic isolators reinforced with fiber and a recycled rubber tire matrix

Seismic isolators are passive control devices that reduce the energy transferred from an earthquake to the superstructure, this avoiding damage to building elements. Seismic isolators are classified according to their connection to the structure; for example, unbonded isolators lack mechanical connections with the building. Unbonded fiber-reinforced elastomeric isolators (U-FREIs) are formed of intercalated layers of bidirectional polyester mesh used as reinforcement and agglomerated ground rubber from end-of-life tires (ELTs) as an elastomeric matrix. This paper presents the mechanical behavior of U-FREIs built at a reduced scale to provide an affordable alternative for the mitigation of seismic forces that affect low-rise buildings. The isolators were designed for a low-rise residential frame structure located in an area of high seismic hazard and were subjected to shear and compression tests to characterize their mechanical behavior. The experimental results show good behavior of the prototypes with respect to standards and design requirements.

Material processing conditions effect on the thermokinetics of end of life tyres

ABSTRACT In this work, end of life tyres (ELTs) samples were subjected to pyrolysis in a dynamic thermogravimetry set-up under various heating rates between 5°C and 25°C min−1. The experimental design involved dried and non-dried sample results in an isothermal step within the heating program, to be able to compare the data against non-dried samples, to further investigate the effect of drying on the results obtained. The drying of the samples resulted in an increase in the onset temperature by some 30°C. However, cryomilling the ELTs samples showed a great effect in reducing the onset of the degradation curve by about 10°C amongst the same set of experiments. The type of sample, in terms of size and processing/milling condition, had a significant impact on the heat flow properties and calorimetry reported. The exothermic region for the original shavings resulted in an enthalpy of −48 J g−1, whilst the cutting mill samples exhibited an enthalpy increase to −184 J g−1. However, the cryomilled samples showed an enthalpy increase estimated at 139 J g−1.

Investigation on Civil Engineering Application of Tyre Encased Soil Element: Laboratory Direct Shear Test and Supply Chain Analysis

The reuse of end-of-life (EOL) tyres as earth reinforcement materials in civil engineering projects have been studied for decades. Entire EOL tyres infilled with compacted soil can form segmental tyre encased soil elements (TESEs) with considerable load-bearing capacity. The TESEs can be used to construct structures like low-rise buildings, railway foundations and geotechnical structures. One of the most important aspects of TESE systems, i.e., the shearing interaction between neighbouring units is not yet well understood. In this study, thirty-six laboratory tests have been conducted to investigate the response of TESEs under intercourse shear actions. This was followed by a supply chain environment and economic analysis to investigate the acceptability of the system. The results revealed that the type of encased soil had more effect on the interface interactions between courses of TESEs compared to the TESEs’ construction pattern. It was also found that the frictional coefficient could be increased by either using coarse and angular aggregates as the encased soil or reducing the amount of the encased soil to form a high portion of rubber-to-rubber contact at the composite interface. Supply chain environment and economic analysis revealed that using entire tyres as construction materials has low CO2 emission and considerable economic benefits.

Evaluation of the effects of textile fibre derived from end-of-life tyres (TFELT) on the rheological behaviour of asphalt binders

End-of-Life Tyres (ELT) consist of rubber, steel and textile fibre (TFELT). Unlike rubber and steel, the possibilities for the re-use of TFELT are limited, and its final disposal is an environmental problem. This article explores an alternative re-use of TFELT as an additive for asphalt binder (AB). The TFELT was characterised using scanning electron microscope (SEM), polarized microscopy and thermogravimetric analysis. Two Asphalt Binders (AB14 and AB24) and three addition percentages (0.1%, 0.3% and 0.5%) were evaluated. The effects on the physical properties at high, intermediate and low temperature were studied by determining the softening point, penetration and FRAASS breaking point. We also evaluated the effects on the rheological properties, by determining the rutting and fatigue parameters at different states of ageing (short and long term). Resistance to the accumulation of deformations was measured by applying the Multiple Stress Creep Recovery test (MSCR), and resistance to fatigue by the Linear Amplitude Sweep test (LAS). The results showed significant effects in reducing the accumulation of permanent deformation, by up to 40% for the addition of 0.5% TFELT, without any reduction in properties of resistance to thermal cracking.

Study of the Effect of the Use of Asphalt Binders Modified with Polymer Fibres from End-of-Life Tyres (ELT) on the Mechanical Properties of Hot Mix Asphalt at Different Operating Temperatures.

Processing of end-of-life tyres (ELT) produces polymer fibres (PFELT) as a by-product. PFELT currently presents a challenge to the recycling industry, due to the increasing numbers of ELT and lack of alternatives for the re-use of this material. The object of this investigation was to propose an alternative for re-using PFELT, in order to improve the performance properties of hot mix asphalt (HMA). This study enabled us to understand the relation between the addition of polymer fibre to the aggregate-binder matrix of the HMA in depth, as well as its effects on the mechanical properties of the resulting asphalt mix. To do this, we first made a physical and chemical characterization of the PFELT (TGA, SEM, polarized light, and fluorescence microscopy), establishing a modification methodology using two asphalt binders (CA-24 and CA-14) and three PFELT contents (0.1%, 0.3%, and 0.5%). The HMA was designed using the Marshall method. The mechanical performance of the HMA was evaluated in a range of operating temperatures, from -10 °C to 50 °C, observing the following properties: (1) resistance to thermal cracking; (2) stiffness modulus; (3) indirect tensile strength; and (4) resistance to permanent deformation. The results show that the addition of 0.3% and 0.5% of PFELT to the asphalt binder significantly improved the mechanical performance properties of the mixes studied, with a greater effect at high operating temperatures; the resistance to permanent deformation increased by more than 30%.

Effect of rubber size and shape on Proctor elements of CBC mixtures

The application of recycled rubber in cement bound base courses (CBC) has recently become a subject of research. There are several advantages of the application of rubber in CBC. One is the environmental benefit considering the major problem of disposing of end-of-life tires (ELT), whose number is rapidly increasing in the modern world. On the other hand, CBC is known as the most rigid course of pavement, and is very prone to cracking. Rubber has the potential to reduce the cracking, which is another benefit of its use in those courses. This paper presents laboratory research on a reference mixture and five rubberized mixtures with different fractions of recycled rubber. The mixtures are modified with 20 % of rubber as a replacement for sand. Three fractions of granulated rubber and two fractions of rubber threads are used. The research encompasses the impact of rubber of different sizes and shapes on the Proctor elements of the CBC mixture. Furthermore, specific surface area (SSA) and SEM analysis is presented. The SSA value was found to be the most influential factor on the optimal moisture content (OMC) values, which is confirmed by SEM images. SEM analysis showed that larger particles have a flatter surface and demand higher water content. Furthermore, the rubber particle shape has a greater impact on the mixture MDD compared to the particle size, while the rubber particle size has a greater effect on the OMC compared to the rubber particle shape. Finally, the effect of the rubber particle size and shape on the OMC and MDD can be neglected and the production of cement bound aggregate incorporating waste rubber can be designed and built using reference values of the OMC and MDD.

A Long-Term Study on the Content of Polycyclic Aromatic Hydrocarbons in Rubber from End-of-Life Tires of Passenger Cars and Trucks.

At the European level, limits have been set (REACH) for the content of polycyclic aromatic hydrocarbons (PAH) in products with rubber and plastic components that come into contact with human skin or the oral cavity. These limit values reported in Commission Regulation (EU) 1272/2013 are of particular importance for the utilization of end-of-life tires (ELT) as recycled rubber materials for consumer applications, but a suitable analytical method has not yet been specified. On the other hand, comprehensive measurement series of the PAH content of ELT materials are scarce in the context of compliance testing against this regulation and general published PAH levels in ELT materials are often based on very different analytical methods. In the present work, the PAH content of three different rubber granulates from ELT (obtained from whole truck and passenger car tires and truck tire treads) were investigated over a period of two years. The Grimmer method was used for PAH profile analysis, which in terms of extraction intensity and sample preparation not only meets the requirements for a reliable determination of the EU priority PAH, but in addition covers a more comprehensive PAH profile. A total of 26 different PAH compounds, including the 8 EU priority PAH (REACH) and the 16 U.S. EPA priority PAH, were analyzed and their variations over time were examined to obtain reliable current data for PAH content in rubber granulates produced from ELT.

Sustainable Reuse of Waste Tire Textile Fibers (WTTF) as Reinforcements.

Waste tire textile fibers (WTTF), as a by-product (10–15% by weight of tires) of end-of-life tires (ELT) mechanical recycling (grinding), are classified as hazardous wastes and traditionally burnt (thermal recycling) or buried (landfilling), leading to several environmental and ecological issues. Thus, WTTF still represent an important challenge in today’s material recycling streams. It is vital to provide practical and economical solutions to convert WTTF into a source of inexpensive and valuable raw materials. In recent years, tire textile fibers have attracted significant attention to be used as a promising substitute to the commonly used natural/synthetic reinforcement fibers in geotechnical engineering applications, construction/civil structures, insulation materials, and polymer composites. However, the results available in the literature are limited, and practical aspects such as fiber contamination (~65% rubber particles) remain unsolved, limiting WTTF as an inexpensive reinforcement. This study provides a comprehensive review on WTTF treatments to separate rubber and impurities and discusses potential applications in expansive soils, cement and concrete, asphalt mixtures, rubber aerogels and polymer composites.

Dynamic Permittivity Measurement of Ground-Tire Rubber (GTR) during Microwave-Assisted Devulcanization.

Many efforts are being made to find innovative ways of recycling rubber from end-of-life tires (ELTs), also called ground tire Rubber (GTR). Recycling through devulcanization allows the reintroduction of rubber back into the manufacturing industry. Such a process requires providing enough energy to break the sulfur links, while preventing damage to the polymeric chain. Microwave heating is controllable, efficient, and it does not rely on conventional heating mechanisms (conduction, convection) which may involve high heating losses, but rather on direct dielectric heating. However, to adequately control the microwave-assisted devulcanization performance, a thorough knowledge of the GTR permittivity versus temperature is required. In this work, GTR permittivity was monitored during its devulcanization. A resonant technique based on a dual-mode cylindrical cavity was used to simultaneously heat rubber and measure its permittivity at around 2 GHz. The results show sharp changes in the GTR permittivity at 160 and 190 °C. After the GTR cooled down, a shifted permittivity evidences a change in the GTR structure caused by the devulcanization process. Microwave-assisted devulcanization effectiveness is proven through time-domain nuclear magnetic resonance (NMR) measurements, by verifying the decrease in the cross-link density of processed GTR samples compared to the original sample.

Pyro-gas analysis of fixed bed reactor end of life tyres (ELTs) pyrolysis: A comparative study

Pyrolysis of end of life tyres (ELTs) present a promising alternative to their incineration or classical product recovery using mechanical means. It can produce light hydrocarbons (HCs) and other valuable chemicals as part of the pyro-gas stream it generates. In this work, two grades of tyres namely a fresh (virgin) one and a waste disposed ELTs, were used as a feedstock to analyse their pyro-gas constituents. There wasn't much difference in the maximum conversion rate between both tyre grades where the fresh tyres had an estimated 15.17% conversion and the ELTs was 13.45% conversion (both at 800 °C). The difference herein was attributed to release of free radicals prior to subjecting the samples to pyrolysis due to their history. The analysis of the pyro-gas samples showed a large make of light hydrocarbon (HC) products, namely methane (CH4/C1), ethane (C2H6/C2), ethylene (C2H4), propane (C3H8/C3), propylene (C3H6), n-butane (C4H10), butadiene compounds, carbon mono and dioxide (CO,CO2). Light HCs mimciking natural gas were more abundant in the case of ELTs were C1 was estimated as 14.53% at 500 °C and 16.73% at 800 °C. C2 was also estimated higher than the fresh tyres where a 11.78% at 500 °C was noted and 7.67% at 800 °C. It can be recommended that future integration plans in oil and gas ventures, namely refinery and petrochemical complexes, are to start taking responsible measures towards the environment by substituting part of their operations with sustainable feedstock such as ELTs.

Development of a New Additive Based on Textile Fibers of End-of-Life Tires (ELT) for Sustainable Asphalt Mixtures with Improved Mechanical Properties.

End-of-life tires (ELT) are a worldwide problem. Rubber, steel, and different textile fibers are the by-products of ELT. Unlike rubber and steel, waste tire textile fibers (WTTF) are disposed of in landfills or burned. This study developed an additive made with WTTF to be incorporated into conventional hot mix asphalt (HMA), and its performance properties were evaluated. First, a characterization of the WTTF used was made and a manufacture protocol was established. Then, a reference HMA was designed and mixtures with different addition percentages (2%, 5% and 8%) of the WTTF-based additive were evaluated. The mechanical properties studied were stiffness modulus, moisture susceptibility, rutting resistance, stripping, and cracking resistance. The results indicated that the addition of the 2% and 5% WTTF-based additive improved these performance properties. Moreover, all addition percentages of the WTTF-based additive evaluated demonstrated a decrease of over 29% in permanent deformation according to the Hamburg Wheel Tracking Test. Thus, the use of the WTTF would not only be valuing a waste, but an asphalt mixture with improved properties would be obtained, contributing to the circular economy by reusing a material and prolonging the useful life of the asphalt mixture.

The role of temperature profile during the pyrolysis of end-of-life-tyres in an industrially relevant conditions auger plant

Pyrolysis is a chemical recycling process of interest as a means to achieve a sustainable circular economy for end-of-life tyres (ELTs). In the pyrolysis process, ELTs are converted into tyre pyrolysis gas (TPG), tyre pyrolysis oil (TPO) and raw recovered carbon black (RRCB). This work investigates for the first time the effect of different temperature profiles by using a single-auger pyrolysis reactor in an industrially relevant scale (TRL-5). Since the development of this process at this representative scale is quite limited and the temperature profile has not been previously studied, the results achieved in this work can provide a useful database for the development of this process at industrial scale. For this purpose, two different sources of ELTs, commercial truck tyres (CTTs) and passenger car tyres (PCTs), were used. Accordingly, the experimental campaign was conducted using two different incremental temperature profiles (425-550-775 °C and 600-700-800 °C) based on those that can be replicated in an industrial-scale auger pyrolysis plant. For the sake of comparison, two isothermal heating conditions (500-500-500 °C and 600-600-600 °C) were also tested. The results confirmed the remarkable influence of temperature profile on both the distribution and properties of products. The 425-550-775 °C temperature profile was found to enhance limonene production, which is associated with the minimisation of secondary reactions in the first heating zone of the reactor. Additionally, there were very low carbonaceous deposits found in the RRCB because of the high severity of devolatilisation conditions in the third heating zone of the reactor. On the other hand, when the temperature profile was raised, the production of single-ring aromatics, particularly benzene, toluene, ethylbenzene and xylenes (BTEX) significantly increased in the TPO at the expense of limonene. Thus, from this strategy, it is possible to tune the properties of the products depending on the requirements of the application in a single step, getting closer for circular economy in the ELT recycling domain.

Thermal-based experimental method and kinetic model for predicting the composition of crumb rubber derived from end-of-life vehicle tyres

End-of-life vehicle tyres are processed into granulised particles (crumb rubber) for reuse in various industries including building and construction. Crumb rubber compositions vary between batches due to the variability in the source of end-of-life tyres (EOLTs). Therefore, it is essential to develop cost-effective tools for rapid chemical (rubber) composition assessment of EOLT-derived crumb rubber to match engineering requirements. This study evaluated the effectiveness of a thermal-based (experimental and analytical) model in predicting the rubber chemical composition of EOLT-derived crumb exclusively sourced from passenger cars, light off-road vehicles and heavy trucks. A thermal degradation kinetic model based on thermogravimetric analysis (TGA) was used to predict the fractional weight of rubber components in EOLT-derived crumb rubber. Different rubber components present in the crumb rubber were confirmed via Fourier Transform Infrared (FTIR) spectroscopy. The thermal model predicted marginally higher natural rubber content (+5–6%) in heavy truck compared to passenger car tyre-derived crumb rubber. In contrast, the model predicted a slightly higher content (+5–6%) of styrene-butadiene in passenger car-derived crumb rubber. The thermal model successfully predicted the composition of EOLT-derived crumb rubber enabling rapid screening of such products to match engineering applications.