Abstract Tire wear presents a significant sustainability challenge, contributing to material loss and worn particle emissions. While surface roughness is known to influence wear behavior of materials, its effects in the context of experimental fatigue wear of tire tread compounds has received limited attention. This study examines the impact of abrader surface roughness on wear rate, worn particle characteristics, and wear patterns using the Akron abrader with four grit sizes (24, 36, 46, and 60) under controlled conditions. Three tire tread compounds with distinct wear behavior, a silica-filled passenger green-tire tread and two carbon black-filled truck tire treads, were utilized for this study. Abrader surface topography was characterized using a laser profilometer, and worn particle size and wear pattern were analyzed by digital optical microscopy combined with image processing. It was shown that the average equivalent particle diameter increases monotonically with the surface roughness. However, the wear rate went through a minimum at about Ra ≈ 6.7 μm for all three rubbers under the tested condition. High rate of wear on smooth abraders was attributed to the large number of small particles, which was supported by the analysis of the wear pattern and explained by the fracture-mechanics framework.
Abstract Flue gas desulfurization ash (FGDA), a typical industrial solid by-product from coal-fired power plants, has significant environmental and economic implications for its resource utilization. However, FGDA contains chemically unstable calcium sulfite (CaSO₃·0.5H₂O), which may affect the structural and performance stability of rubber composites. In this study, high-temperature oxidation modification was employed to treat FGDA. By adjusting oxidation temperature, heating rate, holding time, and air volume, the CaSO₃ content was reduced from 43.05% to 1.55% under the selected condition (550 °C, 5 °C min⁻¹, 40 min, air volume 4.2 L). The modified desulfurization ash was then evaluated at 15 phr in natural rubber (NR) and epoxidized natural rubber (ENR). Compared with untreated FGDA, MFGDA reduced the reversion percentage at 143 °C from 5.70% to 3.88% in NR and from 10.54% to 7.14% in ENR. In terms of mechanical properties, the archived tensile strengths were 21.99 MPa for NR/MFGDA versus 20.91 MPa for neat NR and 17.31 MPa for ENR/MFGDA versus 14.32 MPa for neat ENR; the ENR/MFGDA elongation at break was 718.68% compared with 623.62% for neat ENR. The oxidation treatment did not improve every cure or mechanical parameter, and the aging response depended on matrix and aging time. Overall, the clearest effects were stabilization of the sulfite-rich ash and lower reversion under the tested conditions. Because complete specimen-level replicate data were not available for the historical ash-filled groups, no statistical superiority or optimum MFGDA loading is claimed.
Abstract The tensile stress-strain data of unfilled samples of four rubber polymers (BR, IIR, NR and EPDM) at 5 different crosslink densities are analyzed. Neglecting finite extensibility effects at 1/λ<0.2 and relaxation of temporary entanglements at 1/λ>0.8, the slope of the Mooney stress curve as a function of the inverse stretch 1/λ in the regime of roughly 0.2<1/λ<0.8 was the same for 3 of the four polymers (BR, IIR and NR) at all crosslink densities investigated, allowing a vertical shift to create Mooney master curves. In the case of EPDM, however, the slope of the Mooney plot increased in proportion to the crosslink density below a specific rubber-type dependent shear modulus , and a vertical shift was only possible above . Motivated by these observations, we present a novel strain-energy function which couples the effects of chain orientation and average chain stretch and fully characterizes the stress-strain behavior by use of a single modulus for rubber samples with equilibrium modulus = ≤ . By adding a phantom chain contribution G c for samples with > , and by accounting for finite extensibility and relaxation of temporary entanglements, a consistent modeling of the tensile stress-strain data of all four rubber polymers is possible. For orthotropic deformations (uniaxial stretch and uniaxial compression) analytical solutions of the new strain-energy function and the corresponding stress-strain relations are presented.
ABSTRACT Graphene and its derivatives, such as graphene oxide and reduced graphene oxide, have attracted considerable attention as effective nanofillers for rubber nanocomposites due to their outstanding mechanical strength, large surface area, and excellent thermal and electrical conductivity. We discuss how graphene-based materials can enhance the performance of elastomers, including natural rubber and various synthetic rubbers, with a particular emphasis on achieving uniform dispersion and strong interfacial interactions within the rubber matrix. We outline key synthesis and functionalization approaches for graphene derivatives, along with commonly used processing methods such as solution mixing, in situ polymerization, latex blending, and mechanical compounding. We further examine how the incorporation of graphene influences cure behavior, rheological characteristics—especially the Payne effect—and the overall structure–property relationships of the composites. Improvements in mechanical strength, thermal stability, electrical conductivity, and barrier performance are discussed in relation to filler dispersion and interfacial bonding. Recent progress in theoretical modeling and simulation is also highlighted, offering insights into predicting composite performance and guiding material design. Despite these advancements, challenges such as large-scale processing, consistent dispersion, and a deeper understanding of interfacial mechanisms remain. Overall, we provide a clear and balanced perspective to support the future development and practical application of graphene/rubber nanocomposites.
Abstract A mechanism for amplifying the stiffness of filled rubber compounds—quantified by the dynamic storage modulus (G′)—using a resorcinol/methylene donor-type reinforcing resin (RR) has been proposed and substantiated via a series of rheological and electrical resistivity experiments. The individual and combined effects of filler and RR on G′ were systematically examined, with particular attention given to filler loading, strain-dependent G′ behavior, and the influence of filler surface characteristics. Significant amplification of low-strain G′ (LSG) by RR was observed exclusively in compounds containing interacting fillers at concentrations exceeding their percolation thresholds (typically > ~12 volume %). This G’ amplification effect is further supported by rheological data obtained during vulcanization (via a Moving Die Rheometer (MDR)) and by LSG measured on cured compounds. The extent of this influence is modulated by variations in strain amplitude during MDR testing and by the specific curing protocols employed. The findings suggest that the observed increase in LSG due to RR is primarily attributable to enhanced filler network formation (EFNW). However, the EFNW capability of RR is significantly diminished when the filler surface is heavily occupied by other materials—such as hydrophobating agents used with silica — resulting in a minimal increase in LSG from RR addition. The EFNW mechanism is therefore proposed to arise from RR bridging between filler aggregates. This hypothesis is further supported by the observed decrease in electrical conductivity with increasing RR content, indicating that the conductive pathways within the filler network are disrupted by the insulating nature of RR.
