Hydrogenated acrylonitrile–butadiene rubber (HNBR) is widely used in automotive and sealing applications due to its oil resistance and mechanical durability; however, its long-term performance is significantly influenced by the curing chemistry. Sulfur vulcanization offers superior elasticity but restricted thermal stability, while peroxide curing improves heat resistance at the expense of flexibility. In this study, we investigate hybrid sulfur–peroxide curing to integrate these benefits. The hybrid pathway encompasses competitive and sequential processes, such as partial radical quenching and accelerator oxidation, resulting in a dual crosslink network. Dynamic mechanical, thermal, and temperature scanning stress relaxation (TSSR) evaluations demonstrate that hybrid systems provide precise modulation of the operational temperature–frequency range, broaden the glass-transition relaxation, and control stress dissipation. The coexistence of sulfur and C–C crosslinks results in a heterogeneous structure characterized by diverse crosslink densities and bond energies, leading to numerous relaxation modes and an optimal blend of elasticity, strength, and thermal stability. Microscopy confirms the absence of phase separation, indicating that hybrid vulcanization is a viable approach for producing robust, high-performance HNBR elastomers.

Ground sugarcane bagasse (GSB), an agro-waste rich in lignocellulosic components, was studied as a sustainable bio-filler in natural rubber (NR) tread compounds to lessen reliance on petroleum-derived carbon black (CB). A control formulation with 45 phr CB was compared to hybrid formulations with 40, 35, and 30 phr CB mixed with 5, 10, and 15 phr GSB. Tensile strength 13.1 MPa, elongation at break 700%, and hardness 67 Shore A were all optimally balanced by the compound containing 10 phr GSB (S2), while also exhibiting good cure behavior and thermal stability. Improved tire performance characteristics were confirmed by a dynamic mechanical study, which showed that tan δ at 60 °C decreased by 8.0% (resulting in lower rolling resistance) and increased by 3.9% (improving wet traction) at 0°C. The Payne effect showed improved filler dispersion as a result of GSB partially replacing CB. The results show that appropriately dispersed GSB can partially reinforce NR, enhancing energy efficiency and sustainability. However, larger GSB loadings decrease modulus, tear strength, and abrasion resistance due to lower interfacial adhesion and the presence of micro-voids. According to this study, pulverized sugarcane bagasse shows promise as an environmentally friendly filler for green tire applications, promoting the circular economy and lowering the carbon footprint of rubber compounding.

The present study has proposed a straightforward method to improve the reprocessability of modified natural rubber (NR) by blending it with gelatin (GT). The reprocessable characteristics of these blends were evaluated based on their remolding capabilities and mechanical recovery performance. In this method, poly(vinylbenzyl chloride) (PVBC) was first grafted onto NR chains to create graft copolymers known as NR-g-PVBC. The benzyl chloride groups in the graft copolymers were subsequently converted into quaternary ammonium groups, referred to as NR-g-QPVBC. This modification enabled ionic crosslinking when NR-g-QPVBC reacted with ethylenediamine tetraacetic acid. Blends were created by incorporating GT powder into the NR-g-QPVBC latex. The optimal loading level of GT was determined to be 30 wt%, as the resulting film exhibited the highest recovery of tensile properties. Initially, the film's tensile strength was measured at 15 MPa. After being remolded at 160 °C, the tensile strength decreased to 9.3 MPa, resulting in a recovery rate of 60.7% and withstanding a tensile strain of 144%. Although the NR-g-QPVBC/GT films could be remolded, their tensile properties declined with increasing remolding cycles. Therefore, this work demonstrated a practical method for producing NR-based films that could be reshaped through hot-pressing after being formed into products, increasing their reusability.

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.

Cross-linking frequently enhanced the mechanical properties of linear polymeric materials; however, it also resulted in the transition from thermoplastic to thermosetting materials, which posed issues from an environmental perspective. Thermoplastic polyurethane (TPU) elastomers were extensively applied across various industries. To improve the mechanical properties of TPU while preserving its environmental benefits, this study integrated radical copolymerization technology to develop a reversible crosslinked TPU. Specifically, the linear polyurethane molecular chains were crosslinked using diallyl disulfide (DADS) as a functional cross-linking monomer. Through radical copolymerization reactions, reversible crosslinks formed from disulfide bonds were created between the linear polyurethane molecular chains, yielding a self-healing reversible crosslinked thermoplastic polyurethane (DSTPU). The study showed that DSTPU could self-heal and dissolve under UV light and alkaline N,N-dimethylformamide (DMF) conditions, achieving 82.2% self-healing efficiency at 3 phr DADS. It dissolved into fine particles in alkaline DMF. Disulfide bonds in DSTPU enhanced cross-linking, boosting 19% oxygen permeability, thermal conductivity (0.218 W/(m·K)), and mechanical properties like tensile stress (11.18 MPa), force (134.13 N), and elongation (548%). These bonds also enhanced aging resistance, cutting ΔYI to 6.0%.