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Accelerators are indispensable additives in rubber vulcanization reactions. Hypo-sulfonamide accelerators are widely used due to their fast vulcanization speed. However, the short vulcanization induction period compromises the processing safety of rubber. In this paper, we incorporated experiments with molecular simulations to investigate the underlying reasons for the different effects of various hypo-sulfonamide accelerators The vulcanization induction period of each accelerator was investigated according to the vulcanization curves. Furthermore, the corresponding reaction mechanism was explored from the molecular scale through quantum mechanical and molecular dynamics simulations. Subsequently, the research focus was discussed in depth. The compatibility relationship between the accelerators and the rubber materials w7as verified through the crosslinking density test, and a coincidence between the experimental and simulation results was found. This study guides the selection and improvement of hypo-sulfonamide accelerators and corroborates the factors influencing the vulcanization induction period of natural rubber by accelerators. Highlights * Reactivity of accelerators calculated by quantum mechanical simulations. * Difference in solubility parameter characterizes accelerator/NR compatibility. * Mobility and diffusion coefficient reflect the diffusion ability of the promoter. * Molecular simulation results are consistent with experimental results. KEYWORDS hypo-sulfonamide accelerator, molecular dynamics simulation, natural rubber, quantum mechanics simulation, vulcanization induction period, 1 | INTRODUCTION Vulcanization involves heating the rubber with additives (i.e., sulfur) to transform the linear rubber molecular chain into a three-dimensional mesh structure, achieving the transition of the plastic [...]

In this article, the finite element analysis (FEA) combined with the fracture mechanism of rubber was used to predict the fatigue life of the radial tire carcass rubber. Five tire structures with different angles were designed under the premise of ensuring the same height of carcass cord and radius of curvature. The fatigue life prediction of tires was performed using the Lake-Lindley model in combination with finite element models and crack extension tests. The location and causes of damage in 11.00R20 load radial tires were analyzed, and the effect of sleeve cord angle on tire mechanical properties and fatigue performance was investigated to predict the fatigue life of the radial tire carcass rubber. The simulation test results are within 10% error when compared with the actual durability test results, which can fully meet the daily design development of tire enterprises. The fatigue life prediction method can shorten the development cycle and reduce the development cost of tires. Improving tire durability is important for reducing the use of petrochemical materials and environmental pollution. KEYWORDS carcass cord, crack extension experiment, fatigue life, finite element analysis, tire design, 1 | INTRODUCTION With the rapid development of the economy, the demand for transportation is gradually increasing. Road transport has been moving towards heavy-duty, high-speed, and efficient. The tire is [...]

In the context of environmental protection and energy consumption reduction, reducing the rolling resistance of mining machinery tires is one of the important methods to achieve the goal of green mining. This study probes the effects of wet mixing with a wet carbon black masterbatch on the rolling resistance and grounding performance of wide‐body vehicle tire treads by investigating the cross‐linking structure, rubber–filler (R–F) interaction force, and physicomechanical properties of the wet mixing rubber compounded with a wet carbon black masterbatch. The results indicate decreases in the maximum torque‐minimum torque difference, cross‐link density, and R–F interaction of the wet mixing rubber and increased filler–filler (F–F) interaction and carbon black dispersion. Meanwhile, the tensile elongation of the wet mixing rubber increases, its DIN abrasion property improves, and its Tanδ decreases at 60°C. A numerical method to estimate tire steady‐state rolling resistance is also developed. Finite element simulation analysis reveals that the steady‐state rolling resistance of the wet mixing rubber is reduced by 7.04% at 100% standard load, and its grounding performance is enhanced. By proposing a method to reduce the rolling resistance of tires, this study also provides a reference for the development of wide‐body vehicle tires. Highlights: Explored the filler interaction of wet mixing rubber.Explained the low energy loss of wet mixing rubber.Proposed a new finite element method for calculating tire rolling resistance. [ABSTRACT FROM AUTHOR]

Nitrile rubber (NBR)/hydrogenated nitrile butadiene rubber (HNBR) blends with various ratios were compounded with internal mixer and two-roll open mill. Mechanical properties and low-temperature performance (TRIO) of the NBR/HNBR blends after aging under different conditions were investigated. Furthermore, equilibrium swelling test and moving die rheometer (MDR) test were used to systematically investigate the effects of HNBR dosage on the crosslink densities and curing behaviors. Vulcanization torque and crosslink densities decreased with an increase in HNBR content. The crosslink density of pure HNBR is higher than that of pure NBR, which is related to the macromolecular structures of the rubber. Compression sets of the NBR/HNBR vulcanizates were correlated with HNBR dosage indicating a linear relationship. Low-temperature performance of the NBR/HNBR blends was improved after being aged in the synthetic hydrocarbon hydraulic oils (SH-1 and SH-2). This work shows that the low-temperature performance and oil resistance could be better balanced by blending NBR with HNBR, while the mechanical properties maintain relatively high level. KEYWORDS curing characteristics, hydrogenated nitrile rubber, low-temperature performance, mechanical properties, nitrile rubber, 1 | INTRODUCTION Nitrile rubber (NBR) is one of the synthetic rubbers made of butadiene and acrylonitrile by emulsion polymerization. It has excellent chemical and wear resistance, which is widely [...]

Equilibrium swelling and rheological tests were adopted to systematically investigate the effects of softener type and dosage on the crosslink densities. The results turned out that the chemical crosslink density could be distinguished from the physical crosslink density by comparing the results of equilibrium swelling and rheological tests. The liquid butadiene (LB) as a softener leads to the greatest reduction in crosslink density, followed by polyethylene wax (PW) and paraffinic oil (PO). The tensile strength decreases with increasing PO content while shows peak values with increase of LB and PW contents. The dependencies of chemical crosslink density on the aging time under 150[degrees]C are quite different for the three softeners, which can be expected from the double crosslinking networks consisting of small softener and large main crosslinking networks. Further investigation has been performed to correlate the tensile strength with chemical crosslink density of ethylene propylene diene monomer elastomer vulcanizates. Three different linear relationships can be obtained for the softeners independent of the aging time. It can now be expected from this study that the role of some new softeners in rubber compounds is not only confined to plasticization but also forms crosslinking networks in the peroxide-cured rubbers. KEYWORDS crosslink density, EPDM, equilibrium swelling, softener, tensile strength, 1 | INTRODUCTION Ethylene propylene diene monomer elastomer (EPDM) as one of the most important synthetic rubbers has many advantages in excellent resistance to ozone, oxidation, and weathering over other [...]

Highlights This paper investigated the dispersion of silica exhibiting different specific surface areas in nitrile rubber (NBR) matrices and the interactions between fillers, filled rubber, and rubber networks by regulating the aggregate size. To better characterize and leverage the filler network structure, a comprehensive analysis was conducted using linear and nonlinear rheological tests based on the equilibrium solvation theory and pipe models. The results demonstrated that the incorporation of fillers formed an island‐like network structure. With high specific surface area, the concurrent use of high and low specific surface area silica fillers improved the filler‐rubber interactions and hindered filler‐filler interactions, decreased the filler aggregate size, and enhanced the dispersion. Furthermore, we analyzed the mechanism of the filler network structural enhancement and its relationship with the specific surface area by regulating the filler ratios to adjust the polymer size. Control of Filler Network Structure: Ratio adjustment strengthens interactions. Large silica surface enhances F‐R interaction, small surface improves dispersion. Mixing ratios favor robust filler interconnection or dispersion. Reveals strong correlation of filler network strength with F‐F interactions. Highlighted effective eco‐friendly means of adjusting filler Mixing ratios. [ABSTRACT FROM AUTHOR]

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory–Rehner model and Mooney–Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber. [ABSTRACT FROM AUTHOR]

Protective waxes are typically mixtures of paraffin and microcrystalline waxes that retard the aging of unsaturated rubbers and are widely used in rubber products. The wax solubility of rubber products is important for understanding the migration behavior and film formation of waxes and determining the appropriate wax content in rubber compounds. In this article, protective waxes were applied to natural rubber (NR)/polybutadiene rubber (BR) based sidewall rubber and the compatibility between NR and BR and the protective wax dissolution in these rubbers were investigated with a focus on the former investigation through Materials Studio simulations. It was found that the simulation results are strongly correlated with the wax migration test results on compounded and cured rubber at different NR/BR mass ratios. Blends and mesoscopic dynamics simulations yielded good compatibility between NR and BR and favorable blend morphology. By analyzing the solubility parameter, R value, mean square displacement and diffusion coefficient of wax chains with different lengths in the NR/BR matrix, the mechanism and reasons for the wax precipitation variation of protective waxes at varying NR/BR mass ratios were analyzed from a microstructural point of view, which provides strong theoretical support for the design of the molecular structure of protective waxes. [ABSTRACT FROM AUTHOR]

Mastication can improve the plasticity and reduce the molar mass of natural rubber (NR). The end product properties greatly depend on the efficiency of mastication. For NR before and after mastication, the changes in molecular properties are mainly attributed to the effects of mechanical and thermo‐oxidative degradation. We investigated the variations in molecular weight, molecular weight distribution, degree of branching, and thermal stability of NR after mastication at 35, 75, and 110 rpm for 20 min. The results show that NR has a smaller molecular weight, broader molecular weight distribution, and a lower degree of structural branching at higher rotor speeds. Additionally, the rheological measurements were compared with gel permeation chromatography results, and the comparative outcomes reflect a strong correlation between these data. Rheological analysis reveals considerable complex relationships, and this measurement is more efficient, simple, and convenient than the other technique. [ABSTRACT FROM AUTHOR]

The software package was employed to calculate the three‐dimensional solubility parameters (HSP) of SBR and antioxidants. The HSP values of antioxidants are higher than SBR, meaning that the antioxidants have higher polarity compared with SBR. The solubility measurements of antioxidants in both sulfur and peroxide cured SBR vulcanizates were performed at elevated temperatures from 80 to 130°C. The maximum solubilities (∆S) of antioxidants were correlated with the temperature and also with the new Flory‐Huggins interaction parameters (χN) calculated by the HSP values. The results turn out to be that ∆S increases with increasing temperature as expected and 4020 shows higher ∆S value. Furthermore, ∆S increases with decreasing χN, and by quantitatively mathematical fitting, one functional relationship between ∆S and χN was achieved, regardless of what the crosslinking type of SBR was and what the temperature was involved. Through prediction with χN, one can get that SBR grades with higher styrene content and butadiene/vinyl ratio result in lower χN and accordingly better compatibility with N3100. One of the possible applications of χN is to select suitable SBR and antioxidant structures to design the ever‐increasing SBR‐based green tire tread formula. [ABSTRACT FROM AUTHOR]

Equilibrium swelling test is employed to study the swelling responses of natural rubber (NR) in various solvents, and to determine the total Hildebrand solubility parameter (δt) of NR. The three‐dimensional solubility parameters (HSP) of NR is obtained by virtue of software package as the result of being δd = 17.50 MPa1/2, δp = 3.20 MPa1/2, δh = 1.40 MPa1/2, and δt = 17.85 MPa1/2, respectively. The swelling ratio (q) is correlated with the energy difference (Ra) in order to deeply understand the swelling principle of NR, and the results turn out that q decreased with the increase of the Ra and it can be used to explain the abnormal swelling phenomena of methyl acetate and ethyl acetate. One of the possible applications of Ra is the prediction or explanation of diffusion behaviors of small liquids in the rubber matrix. Therefore, the diffusion coefficient (D) is calculated in accordance with the Fick's law model and attempted to correlate with the Ra value. Two qualitative relationships between D and Ra and χHSP can be preliminarily established now, which can provide an easy way to predict the diffusion behavior of fluids in rubber matrix. [ABSTRACT FROM AUTHOR]