Waste rubber disposal causes considerable negative environmental impacts due to its increase worldwide, mainly in the automotive industry. Therefore, the search for technological solutions for rubber waste is a priority, and the first step in this material degradation is devulcanization due to its difficult degradation. This study evaluated rubber devulcanization using a closed vessel microwave digestion system with nitric acid (HNO₃) and hydrogen peroxide (H₂O₂) through chemical characterization, aiming at verifying the synergistic effect between these oxidizing agents. Microwave irradiation was applied as a heating method to facilitate the chemical reactions, focusing on the synergism between HNO₃ and H₂O₂. Results showed that 5 M H₂O₂ in combination with 1% HNO₃, presented better results. A greater decrease in cross-link density was demonstrated as the concentration of H₂O₂ increased (3.96·10^–5±1.99·10^–6 mol/cm³), likewise, higher sulfates released (926.8±53.4 mg/L), increased mass loss (12.184±1.06%), rubber surface fragmentation, and important variations in the C–S, C=O bands, showing better results when devulcanization is carried out in synergism between HNO₃ and H₂O₂.

Electron beam (EB) treatment of a high vinyl styrene-butadiene-styrene (SBS) block copolymer was accomplished by exposing the polymer to high-energy electrons generated from an electron accelerator. This resulted in the formation of free radicals of carbon on the polybutadiene units in the backbone of the elastomer and subsequent radical coupling to produce cross-links. In the process, some unavoidable chain scission (CS) also occurred. An attempt was made to mathematically trace the nature of the CS as a function of radiation dose with the aid of the experimentally determined cross-link density (CLD), tensile strength and tear strength, the latter three also obtained as functions of radiation dose. The radiation dose was varied from 12.5 to 300.0 kGy in multiples of 12.5 kGy. The novelty of the work was, in part to create a function that can be used to calculate chain-scission in dependence of EB radiation dose. It was found that a change in the ratio of CS to CLD occurred as a function of radiation dose over the previously calculated constant ratio, using the Charlesby-Pinner equation.

Analyzing rubber waste is crucial for value-added recycling, but the multitude of ingredients in vulcanized networks makes it challenging to characterize cross-linked rubbers. A combination of analytical techniques is usually required. In this study, two complementary characterization techniques, based on Fourier transform infrared (FTIR) spectroscopy and derivative thermogravimetric analysis (DTGA) were applied to analyze the structural, physical, and thermal behavior of ground tire rubber (GTR) samples devulcanized by two different processes. A set of samples was devulcanized by only microwaves (MW) while another set was treated with a combination of a thermochemomechanical (TM) process, which included the use of a devulcanization aid such as benzoyl peroxide, and microwaves. The combined technique proved to be more efficient in terms of the degree of devulcanization, significantly reducing the cross-linking density. However, the combined thermochemomechanical and microwave (TM/MW) devulcanization process resulted in greater degradation of the main rubber chains in the cross-linked network compared to the process using only microwaves.

Silicone rubber magnetorheological elastomers (SR-MREs) are increasingly recognized for their resilience in marine conditions, offering prolonged service life and durability. This study evaluates the one-month durability of silicone rubber magnetorheological elastomers (SR-MREs) under seawater conditions. Results revealed a 6% reduction in hardness and an 8% decrease in Young’s modulus compared to unimmersed samples. Morphological and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses supported these findings, revealing surface defects and chemical bonding changes. The immersed SR-MRE displayed a notable 250% increase in elongation at break, highlighting enhanced elasticity. Rheological properties revealed complex mechanical behavior, with an initial increase in storage modulus from 0.25 to 0.38 MPa in the presence of a magnetic field, followed by a gradual decrease to 0.15 MPa at 0 A and 0.52 Mpa at 5 A with strain. Additionally, this study proposes an illustrative mechanism to elucidate the relationship between seawater elements and SR-MRE behavior, enhancing our understanding of its mechanical properties and degradation in marine environments, thus highlighting SR-MRE’s potential as a durable material compared to traditional rubber composites.

The global concern over zinc leaching into aquatic ecosystems has led researchers to seek ways to reduce zinc oxide (ZnO) content in rubber products. Conventional microsized ZnO, commonly used in the rubber industry, poses dispersion challenges due to its hydrophilic nature and micron size within the hydrophobic rubber matrix. Therefore, higher amounts of ZnO are added, elevating the risk to aquatic life. A promising alternative involves using highly dispersible ZnO with active zinc (Zn) centers instead of conventional ZnO. Another approach includes incorporating ZnO-anchored silica particles into the rubber matrix, which requires additional ex-situ fabrication. This study presents an innovative method where ZnO-anchored silica is generated in situ during the blending of styrene-butadiene rubber/natural rubber (SBR/NR). The study also evaluates the effectiveness of active, nano-sized, and octylamine-modified ZnO as activators compared to conventional ZnO, by introducing silica filler, octylamine-modified and high surface area ZnO anchor onto the silica surface, forming Si–O–Zn covalent bonds. This protective layer reduces filler aggregation and the Payne effect. Even with 60% less usage, these activators in the SBR/NR blend significantly enhance tensile strength (31.27%) and elongation at break (49.13%) compared to conventional ZnO. These results point towards the possibility of a cost-effective and sustainable replacement for conventional ZnO.