Search Results (12)

The issue of forming a reliable and stable structure of a crumb-rubber-modified binder is an important scientific and technical task. The authors supplemented existing concepts of the mechanism of effective interaction with rubber crumb by introducing a preliminary first stage: controlled partial physical destruction of rubber crumb—producing rubber reclaim. Proposed physical methods of rubber crumb destruction include high shear force (roll mills), high temperature, and a plasticizing medium. The controllability and degree of devulcanization of rubber were determined by acetone-chloroform extraction in different time intervals. The degree of devulcanization of rubber in the rubber reclaim was found to be 22 ± 0.24%, with stability over 14 days. It was found that the size of the particles of the rubber reclaim in the bitumen is less than 2 µm. The properties of the structure of the binder modified with rubber reclaim, characterizing the stability and sustainability, have been studied and established. The developed modified binders are stable in storage. Rheological parameters of the structure characterizing intermolecular interaction, such as shear stability for original and RTFOT-aged, modified bitumen, meet requirements of the state standard at test temperature 64 °C. The elastic structural component of the crumb-rubber-modified binder, as indicated by the relative irreversible deformation parameter J_3,2, does not exceed 2.6 kPa (<4.5 kPa) at 64 °C. Additionally, it was determined that the rheological structural parameter for fatigue resistance, which characterizes the durability of road pavement under intensive operational conditions, does not exceed 4699 kPa (<5000 kPa) at 16 °C. The use of 10% rubber reclaim combined with waste frying oil provided the opportunity to obtain a modified binder with a stable and sustainable structure without the introduction of additional stabilizers and agents. Test results showed that the overall performance characteristics of the modified binder meet the 64(S)-40 grade standards. Full article

This study explores the potential for recycling natural rubber (NR) latex waste from balloon production through the devulcanization and revulcanization processes. The mechanical devulcanization of colored latex balloon waste was conducted, followed by revulcanization using a sulfur-based system. The reclaimed rubber’s properties, including crosslink density, tensile strength, and abrasion resistance, were compared with those of virgin NR. The results demonstrate that the reclaimed rubber maintains a crosslink density close to that of virgin NR. Hardness and abrasion resistance were comparable, indicating successful material recovery. Structural analyses, including FTIR and SEM microscopy, revealed that the devulcanization process effectively allowed for successful revulcanization. This study concludes that NR latex waste can be effectively recycled and reused in rubber composite formulations, offering a sustainable approach to waste management in the rubber industry and contributing to developing eco-friendly materials. In the context of this research, integrating advanced chemical and physical methods, such as solubility parameter calculations and enhanced devulcanization techniques, could further optimize the devulcanization process. These methods quantitatively enhance the efficiency of material recovery, offering a path to more sustainable recycling practices. The findings suggest that combining such advanced methodologies could significantly improve recycled NR latex’s overall performance and applicability in industrial applications. Full article

The inadequate disposal of tires poses a significant threat to human health and requires effective recycling solutions. The crosslinked structure of rubber, formed through sulfur bridges during vulcanization, presents a major challenge for recycling because it prevents the rubber scraps from being reshaped thermoplastically. Reclaiming or devulcanization aims to reverse this crosslinking, allowing waste rubber to be transformed into products that can be reprocessed and revulcanized, thereby saving costs and preserving resources. Microwave technology shows promise for devulcanization due to its ability to break sulfur crosslinks. In this study, we investigate the devulcanization of ground tire rubber (GTR) through a combined process applied to samples from both car and truck tires subjected to varying periods of microwave irradiation (0, 3, 5 and 10 min). The devulcanized GTR was then blended with natural rubber (NR) and underwent a new vulcanization process, simulating recycling for novel applications. The GTR was mixed with NR in proportions of 0, 10, 30 and 50 parts per hundred rubber (phr). This study also examines the differences between the GTR from car tires and GTR from truck tires. The results showed that the treatment effectively breaks the crosslinks in the GTR, creating double bonds (C=C) and improving the mechanical properties of the revulcanized samples. The crosslinking density and related properties of the samples increased with treatment time, reaching a maximum at 5 min of microwave treatment, followed by a decrease at 10 min. Additionally, the incorporation of GTR enhanced the thermal stability of the resulting materials. Full article

Low-temperature mechanical chemical devulcanization is a process that can produce reclaimed rubber with exceptional mechanical properties. However, the inadequacy and low efficiency of the devulcanization have significantly restricted its application. To address the issues, alcoholic amines, including hydroxyethyl ethylenediamine (AEEA), ethanolamine (ETA), and diethanol amine (DEA), are utilized as devulcanizing agents to promote the devulcanization process. Careful characterizations are conducted to reveal the devulcanizing mechanism and to depict the performances of reclaimed rubbers. Results show that the amine groups in the devulcanizing agents can react with sulfur after the crosslink bonds are broken by mechanical shear force, thus blocking the activity of sulfur and introducing hydroxyl groups into the rubber chains. The incorporation of alcoholic amines can enhance the devulcanizing degree and devulcanizing efficiency, reduce the Mooney viscosity, and improve the mechanical and anti-aging performance. When using DEA as the devulcanizing agent, the sol content of reclaimed rubber increases from 13.1% to 22.4%, the devulcanization ratio increases from 82.1% to 89.0%, the Mooney viscosity decreases from 135.5 to 83.6, the tensile strength improves from 14.7 MPa to 16.3 MPa, the retention rate of tensile strength raises from 55.2% to 82.6% after aging for 72 h, while the devulcanization time is shortened from 21 min to 9.5 min, compared with that without using alcoholic amines. Therefore, alcoholic amines exhibit remarkable advantages in the devulcanization of waste rubber, thus indicating a promising direction for the advancement of research in the area of waste rubber reclamation. Full article

The vulcanization of rubber compounds is an exothermal process. A carbon black-filled and natural rubber-based (NR) formulation was mixed with different levels of sulfur (0.5, 1.0, 2.0, 4.0 and 6.0 phr) and studied with differential scanning calorimetry (DSC) for the determination of the vulcanization enthalpy. It was found that the vulcanization enthalpy is dependent on the amount of sulfur present in the compound and the vulcanization heat released was −18.4 kJ/mol S if referred to the entire rubber compound formulation or −46.0 kJ/mol S if the heat released is referred only to the NR present in the compound. The activation energy for the vulcanization of the rubber compounds was also determined by a DSC study at 49 kJ/mol and found to be quite independent from the sulfur content of the compounds under study. A simplified thermochemical model is proposed to explain the main reactions occurring during the vulcanization. The model correctly predicts that the vulcanization is an exothermal process although it gives an overestimation of the vulcanization enthalpy (which is larger for the EV vulcanization package and smaller for the conventional vulcanization system). If the devulcanization is conducted mechanochemically in order to break selectively the sulfur-based crosslinks, then the natural rubber compounds recovered from used tires can be re-vulcanized again and the exothermicity of such process can be measured satisfactorily with DSC analysis. This paper not only proposes a simplified mechanism of vulcanization and devulcanization but also proposes an analytical method to check the devulcanization status of the recycled rubber compound in order to distinguish truly devulcanized rubber from reclaimed rubber. Full article

In this paper, low-temperature extrusion of ground tire rubber was performed as a pro-ecological waste tires recycling method. During this process, ground tire rubber was modified with constant content of dicumyl peroxide and a variable amount of elastomer (in the range: 2.5–15 phr). During the studies, three types of elastomers were used: styrene-butadiene rubber, styrene-ethylene/butylene-styrene grafted with maleic anhydride and ethylene-octene copolymer. Energy consumption measurements, curing characteristics, physico-mechanical properties and volatile organic compounds emitted from modified reclaimed GTR were determined. The VOCs emission profile was investigated using a passive sampling technique, miniature emission chambers system and static headspace analysis and subsequently quantitative or qualitative analysis by gas chromatography. The VOCs analysis showed that in the studied conditions the most emitted volatile compounds are dicumyl peroxide decomposition by-products, such as: α-methylstyrene, acetophenone, α-cumyl alcohol, methyl cumyl ether, while the detection level of benzothiazole (devulcanization “marker”) was very low. Moreover, it was found that the mechanical properties of the obtained materials significantly improved with a higher content of styrene-butadiene rubber and styrene-ethylene/butylene-styrene grafted with maleic anhydride while the opposite trend was observed for ethylene-octene copolymer content. Full article

Common swelling agents used in the mechano-chemical rubber devulcanization process usually require high temperatures to achieve satisfactory swelling effects, which results in severe production of pollutants and reduces the selectivity of bond scissions. This work presents an environmentally friendly swelling agent, terpinene, which can swell the rubber crosslink structures at low temperatures. Both a rubber swelling experiment and a rubber reclaiming experiment with a mechano-chemical devulcanization method are conducted to explore the swelling effects of terpinene. After soaking in terpinene at 60 °C for 90 min, the length elongation of the rubber sample reaches 1.55, which is much higher than that in naphthenic oil and is comparable to that in toluene. When adding 3 phr of terpinene for every 100 phr of waste rubber during the reclaiming process, the bond scissions exhibit high selectivity. After revulcanization, the reclaimed rubbers have a tensile strength of 17 MPa and a breaking elongation of 400%. Consequently, the application of terpinene as the swelling agent in the LTMD method can greatly improve the properties of reclaimed rubbers, thereby enhancing the dual value for the economy and environment. Full article

Despite technological developments, modern methods for the disposal of end-of-life tires most often involve either their incineration in cement kilns or the destruction of tires in special landfills, demonstrating a lack of sustainable recycling of this valuable material. The fundamental role of recycling is evident, and the development of high-efficiency processes represents a crucial priority for the European market. Therefore, the investigation of end-of-life rubber processing methods is of high importance for both manufacturers and recyclers of rubber materials. In this paper, we review existing methods for processing of end-of-life tires, in order to obtain rubber crumb, which can later be used in the production of new industrial rubber goods and composites. We consider processes for separating end-of-life tires into fractions (in terms of types of materials) using chemical, mechanochemical, and mechanical methods to process the materials of used tires, in order to obtain crumb rubber of various fractions and chemical reactivities. Full article

Improper disposal and storage of waste tires poses a serious threat to the environment and human health. In light of the drawbacks of the current disposal methods for waste tires, the transformation of waste material into valuable membranes has received significant attention from industries and the academic field. This study proposes an efficient and sustainable method to utilize reclaimed rubber from waste tires after devulcanization, as a precursor for thermally rearranged (TR) membranes. The reclaimed rubber collected from local markets was characterized by thermogravimetric analyzer (TGA) and Fourier transfer infrared spectroscopy (FT-IR) analysis. The results revealed that the useable rubber in the as-received sample amounted to 57% and was classified as styrene–butadiene rubber, a type of synthetic rubber. Moreover, the gas separation measurements showed that the C7-P2.8-T250 membrane with the highest H₂/CO₂ selectivity of 4.0 and sufficient hydrogen permeance of 1124.61 GPU exhibited the Knudsen diffusion mechanism and crossed the Robeson trade-off limit. These findings demonstrate that reclaimed rubber is an appealing, cost effective, and sustainable alternative, as a precursor for TR membranes, for application in gas separation. The present approach is useful in the selection of a suitable reclaimed rubber precursor and related membrane preparation parameters, leading to the advancement in the recycling value of waste tires. Full article

Ground tire rubber (GTR) was processed using an auto-thermal extrusion as a prerequisite to green reclaiming of waste rubbers. The reclaimed GTR underwent a series of tests: thermogravimetric analysis combined with Fourier-transform infrared spectroscopy (TGA-FTIR), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and static headspace and gas chromatography-mass spectrometry (SHS-GC-MS) in order to evaluate the impact of barrel heating conditions (with/without external barrel heating) on the reclaiming process of GTR. Moreover, samples were cured to assess the impact of reclaiming heating conditions on curing characteristics and physico-mechanical properties. Detailed analysis of the results indicated that the application of auto-thermal extrusion is a promising approach for the sustainable development of reclaiming technologies. Full article

The devulcanization of the rubber wastes in autoclave represent a technological variant that allows the superior utilization of rubber wastes, but with high energy consumption. The researches aimed at improving the devulcanization technology in order to obtain reclaimed rubber with superior characteristics, but also with a reduction in energy consumption. An improvement to devulcanization technology consisted in vacuuming the autoclave at the end of the devulcanization process. An increase in the degree of devulcanization of the rubber from 86.83% to 93.81% and an improvement of the physico-mechanical characteristics of the reclaimed rubber was achieved by applying this technology. The realization of the new type of regenerated rubber allowed for an increase in the degree of it use for different mixtures, from 15–20 phr to 30–40 phr without substantially affecting the physical and mechanical properties of the products. Additionally, the researche has shown that, by obtaining the new type of reclaimed rubber, the duration of the refining process has been reduced by 30%. All of this leads to a considerable reduction in energy consumption and transformation of the rubber waste reclaiming process into a sustainable one. Full article

Ground tire rubber (GTR) was mechano-chemically modified with road bitumen 160/220 and subsequently treated using a microwave radiation. The combined impact of bitumen 160/220 content and microwave treatment on short-term devulcanization of GTR was studied by thermal camera, wavelength dispersive X-ray fluorescence spectrometry (WD-XRF), static headspace, and gas chromatography-mass spectrometry (SHS-GC-MS), thermogravimetric analysis combined with Fourier transform infrared spectroscopy (TGA-FTIR), oscillating disc rheometer and static mechanical properties measurements. The obtained results showed that bitumen plasticizer prevents oxidation of GTR during microwave treatment and simultaneously improves processing and thermal stability of obtained reclaimed rubber. Full article