Search Results (141)

The study investigates the influence of a hybrid filler system based on carbon black, silica (SiO₂) and shungite from the Bakyrchik deposit on the curing behavior of rubber compounds as well as on the physical–mechanical properties and thermal stability of vulcanizates based on a blend of butadiene-alpha-methylstyrene and isoprene rubbers. The morphology and elemental composition of shungite were examined using SEM-EDS analysis. Thermogravimetric analysis of shungite was also performed. The introduction of shungite led to a decrease in Mooney viscosity and an increase in scorch time. Rubber composites containing 10–20 phr (parts per hundred rubber) of shungite exhibited a satisfactory balance between the processing properties of the rubber compounds and the physical–mechanical properties of the vulcanizates (tensile strength, elongation at break, and rebound resiliency), which makes them promising for practical application. When 10 phr of shungite was added, the tensile strength of the rubber composites after thermal aging remained at the level of the control sample, while the changes in elongation at break, rebound resilience, and hardness were less pronounced than in the control. Full article

This work aimed to investigate the properties of cross-linked elastomeric blends based on natural rubber (NR) and chloroprene rubber (CR), incorporating plant-derived fillers as environmentally friendly additives. The selected eco-friendly biofillers included ginseng, lemongrass, turmeric, or wood flour. In situ surface modification with n-octadecyltrimethoxysilane was carried out to enhance the compatibility between the fillers and the elastomeric matrix. The results showed that both unmodified and silane-modified plant-based fillers can be effectively used in NR/CR composites, yielding vulcanizates with favorable performance characteristics. The ginseng-filled composite exhibited the highest degree of cross-linking and superior mechanical strength among the tested materials. Turmeric, in both its unmodified and silane-treated forms, contributed to the greatest resistance against aging factors. Notably, the silane-modified wood flour filler significantly improved tear resistance, nearly doubling that of the unfilled rubber. Overall, these novel rubber composites demonstrate not only promising functional properties but also considerable ecological and economic advantages. Full article

Rubber is a crucial sealing material in the petroleum industry. Due to increasingly stringent industrial development, safety performance requirements are becoming extremely high, resulting in higher oil resistance requirements for rubber. HNBR exhibits good heat resistance, high tensile strength, tear strength, and excellent wear resistance. However, a certain degree of aging will also occur in the actual service process, which will affect the service life of rubber. In order to explore the factors affecting the aging behavior of HNBR vulcanizates in an oil–water environment at 150 °C, HNBR vulcanizates were aged in an independent environment. IR (Infrared) spectroscopy analysis (FTIR), crosslinking density analysis, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM) testing were used to characterize the microstructural and morphological changes in HNBR vulcanizates before and after aging. The aging mechanism of HNBR vulcanizates in different environments was obtained. Since factors such as rubber fillers remained constant throughout the experimental process, the influence of formulation variables on aging was disregarded. Full article

End-of-life tires (ELTs) are an important source of energy and materials, with ELT powder (ELTp) being a secondary raw material of increasing industrial interest. However, the complex structure and composition of ELTp rubber pose technological difficulties and scientific challenges in some high-performance applications in the rubber industry. The mechanical recycling of ELTp produces ground tire rubber (GTR) powder, which is used, among other applications in the rubber field, to prepare thermoplastic vulcanizates (TPVs) due to the interest in these materials in the automotive and construction sectors. Over the last few decades, different approaches have been explored to minimize the limitations of these TPVs, including their large particle size and poor compatibility with GTR powder in other polymer matrices. This study applies different recycling procedures to GTR powder, based on thermal, chemical and mechanical methods, and combinations thereof, to minimize interfacial issues with other matrices used in TPV preparation. The effect of the different rubber recycling processes on the performance of the resulting TPVs was evaluated, optimizing the fraction of recycled rubber from ELTp and the vulcanization system to enhance the mechanical properties and obtain industrially competitive products. Full article

Recycling end-of-life rubber to compound components for new formulations is one of the most promising ways to reach the sustainability goals of the rubber industry. Today, devulcanization and pyrolysis are both methods to reuse crosslinked elastomers. A third recycling approach is to process end-of-life rubber into ground rubber (GR), which is then added to green compounds. However, free sulfur diffuses during mixing, storage and vulcanization from the matrix material into the GR particles. As a result, the crosslink density in the matrix is reduced, which deteriorates the in-rubber properties of GR-containing vulcanizates compared to those that do not contain GR. Therefore, GR particles are mainly used today for rubber parts with less demanding dynamic-mechanical requirements, which limits the use of the particles. This study presents an approach for reducing the sulfur diffusion from the matrix into the GR particles by prevulcanizing the green matrix material. This leads to GR-containing vulcanizates with significantly improved mechanical properties. This new approach shows that the quality of the recycled rubber product can be significantly increased by blocking the sulfur diffusion. Even though such prevulcanization is currently only feasible under laboratory conditions, it might also pave the way for finding solutions in a production scale for an effective incorporation of GR into new rubber compounds. Full article

The increasing demand for sustainable materials has propelled the development of bio-based elastomers derived from renewable terpenes. This study presents the synthesis of high-cis poly(butadiene-co-terpene) copolymers using coordination chain transfer polymerization with neodymium-based catalysts, enabling precise control of molecular weight and microstructure. Two terpene monomers, β-myrcene and trans-β-farnesene, were incorporated up to 45 wt% without compromising the elastomeric 1,4-cis polybutadiene segments. The copolymers were evaluated as impact modifiers in acrylonitrile–butadiene–styrene (ABS) and as vulcanizable rubber formulations. ABS containing bio-based copolymers exhibited distinct rubber morphologies, including elongated and rod-like particles with average particle diameters greater than 1042 nm and rubber phase volume fraction values ≥ 0.49, resulting in improved impact resistance exceeding 580 J/m and elongation at break higher than 12%. Vulcanized rubbers incorporating terpene segments displayed tunable curing kinetics, mechanical properties, and dynamic mechanical behavior, with notable increases in elongation (up to ~520%) and elasticity attributed to lower crosslink density (<1.20 × 10⁻⁴ mol/mL). Additionally, its energy dissipation capacity has been enhanced compared to the high-cis polybutadiene. These findings highlight the potential of terpene-derived bioelastomers as sustainable alternatives to fossil-based rubbers, offering comparable or enhanced performance for engineering polymer applications. The study underscores important structure–property relationships, providing a foundation for further optimization toward industrial adoption. Full article

This study aimed to evaluate the physical properties and biodegradability of sulfur-vulcanized polyhydroxyalkanoates (PHAs) with unsaturated side chains. As a vulcanizable PHA, poly(3-hydroxybutyrate-co-3-hydroxy-5-hexenoate) [P(3HB-co-3H5HE)] was biosynthesized with a 3H5HE fraction of 3–47 mol% using recombinant Escherichia coli and subsequently vulcanized with varying sulfur contents (2–20 per hundred resin, phr) in the presence of zinc oxide, stearic acid, and 2-mercaptobenzothiazole as curing agents. The vulcanized PHA copolymers were insoluble in chloroform, indicating the formation of a cross-linked network. Raman spectroscopy revealed the functional loss of the double bonds in the polymers. After the vulcanization with 5 phr sulfur, the tensile strength and elongation at break of P(3HB-co-47 mol% 3H5HE) increased from 0.6 MPa to 6.3 MPa and from 430% to 813%, respectively. This sample exhibited low tensile set (8%) after 200% elongation, indicating rubber-like properties. Although biodegradability decreased with increasing crosslink density, vulcanized P(3HB-co-3H5HE) exhibited a greater degradation potential than vulcanized rubber but was lower than that of non-vulcanized P(3HB-co-3H5HE). These findings demonstrate that sulfur vulcanization can enhance the resilience of unsaturated PHAs, making them suitable for elastomeric and environmental applications. Full article

By proportionally blending fresh latex from PR107, Reyan 72059, and Reyan 73397, and employing both acid- and enzyme-assisted microbial coagulation methods, this study analyzed the effects of the specific latex formulation on the following: physicochemical properties, non-rubber components, molecular weight and distribution, vulcanization characteristics of compounded rubber, and physical–mechanical properties of vulcanized natural rubber. The results indicate that, compared to acid-coagulated natural rubber, enzyme-assisted microbial coagulated natural rubber exhibits slightly lower levels of volatile matter, impurities, plasticity retention index (PRI), nitrogen content, calcium ions (Ca²⁺), iron ions (Fe³⁺), and fatty acid content. Conversely, it demonstrates higher values in ash content, initial plasticity (P₀), Mooney viscosity (M_L(1+4)), acetone extract, magnesium ions (Mg²⁺), copper ions (Cu²⁺), manganese ions (Mn²⁺), gel content, molecular weight and distribution, and glass transition temperature (Tg). With the increase in the proportion of PR107 and Reyan 72059 fresh latex, the ash content, volatile matter content, fatty acid content, gel content, and dispersion coefficient (PDI) of natural rubber gradually decrease, while the impurity content, PRI, nitrogen content, weight-average molecular weight (Mw), and number-average molecular weight (Mn) gradually increase. Compared to acid-coagulated natural rubber compounds, enzyme-assisted microbial-coagulated natural rubber compounds exhibit higher minimum torque (M_L) and maximum torque (M_H), but shorter scorch time (t₁₀) and optimum cure time (t₉₀). Furthermore, as the proportion of PR107 and Reyan 72059 fresh latex increases, the ML of the compounds gradually decreases. In pure rubber formulations, enzyme-assisted microbial-coagulated natural rubber vulcanizates demonstrate higher tensile strength, tear strength, modulus at 300%, and Shore A hardness compared to acid-coagulated natural rubber vulcanizates. When the fresh latex ratio of PR107, Reyan 72059, and Reyan 73397 is 1:1:3, the tensile strength and 300% modulus of the natural rubber vulcanizates reach their maximum values. In carbon black formulations, the tensile strength and tear strength of enzyme-assisted microbial-coagulated natural rubber vulcanizates are significantly higher than those of acid-coagulated natural rubber vulcanizates in pure rubber formulations, with the increase exceeding that of other samples. Full article

One of the most important challenges the tire industry faces is becoming carbon-neutral and using 100% sustainable materials by 2050. Utilizing materials from renewable sources and recycled substances is a key aspect of achieving this goal. Petroleum-based oils, such as Treated Distillate Aromatic Extract (TDAE), are frequently used in rubber compounds, and a promising strategy to enhance sustainability is to use bio-based plasticizer alternatives. However, research has shown that the replacement of TDAE oil with bio-based oils or resins can significantly alter the glass transition temperature (T_g) of the final compound, influencing the tire properties. In this study, the theory was proposed that using a plasticizer blend, comprising oil and resin, in a rubber compound would result in similar T_g values as the reference compound containing TDAE. To test this, the cycloaliphatic di-ester oil Hexamoll DINCH, which can be made out of bio-based feedstock by the BioMass Balance approach, was selected and blended with the cycloaliphatic hydrocarbon resin Escorez 5300. Various oil-to-resin ratios were investigated, and a linear increase in the T_g of the vulcanizate was obtained when increasing the resin content and decreasing the oil content. Additionally, a 50/50 blend, consisting of 18.75 phr Hexamoll DINCH and 18.75 phr Escorez 5300, resulted in the same T_g of −19 °C as a compound containing 37.5 phr TDAE. Furthermore, this blend resulted in similar curing characteristics and cured Payne effect as the reference with TDAE. Moreover, a similar rolling resistance indicator (tan δ at 60 °C = 0.115), a slight deterioration in wear resistance (ARI = 83%), but an improvement in the stress–strain behavior (M300 = 9.18 ± 0.20 MPa and Ts = 16.3 ± 0.6 MPa) and wet grip indicator (tan δ at 0 °C = 0.427) were observed. The results in this work show the potential of finding a balance between optimal performance and sustainability by using plasticizer blends. Full article

Carbon black (CB) serves as the most crucial reinforcing filler in natural rubber (NR) applications. However, conventional CB production relies on petroleum or coal resources, raising concerns about non-renewability and unsustainable resource consumption. Although biomass-derived carbon materials have been explored as alternatives for natural rubber reinforcement, their practical application remains constrained by inherent limitations such as large particle size and low graphitic structure, which compromise reinforcement efficiency. This study presents a novel walnut shell biochar (WSB) for natural rubber enhancement. The biochar was prepared via conventional pyrolysis and subsequently subjected to an environmentally friendly physical ball-milling process. This treatment effectively increased graphitized domains while enriching surface functional groups. Systematic investigations were conducted on the effects of ball-milling duration and biochar loading on rubber reinforcement performance. Results demonstrate that the biochar-reinforced vulcanizates achieved a 22% improvement in tensile strength compared to unfilled rubber. Notably, at 10 phr loading, the tensile strength of biochar-filled vulcanizates reached 98% of that achieved by CB(N330)-filled counterparts. The study further revealed that biochar incorporation effectively reduced hysteresis loss and enhanced elastic recovery in rubber composites. This work proposes a facile method to develop sustainable biochar-based reinforcing agents with significant potential for natural rubber applications. Full article

The rapid advancement of big data and artificial intelligence has highlighted the substantial potential of data-driven approaches in polymer material research and development. In the present study, data-driven predictive models were developed to accurately forecast the density, tensile strength, flexural strength and melt mass flow rate of thermoplastic vulcanizate (TPV) rubber. Furthermore, a generation model was used to produce new material formula data for TPV rubber, and predictions were made for the aforementioned properties. The results indicated that the predicted values are in good agreement with experimental data. This study introduces innovative strategies and methodologies for the intelligent design of polymer materials, which could potentially lower research and development costs and accelerate the emergence of novel materials. Full article

Natural rubber (NR) has long been plagued by inferior oil resistance and poor thermal degradation at high temperatures. Despite these limitations, NR remains the most widely used elastomer to date. Fluorine-containing compounds have demonstrated excellent oil resistance and thermal stability. However, they generally exhibit poor compatibility with non-polar polymers. After blending, macroscopic phase separation cannot be easily suppressed, leading to the deterioration of the material’s properties. In this study, fluorination modification was performed using hydroxyl-terminated polybutadiene, and the resulting fluorine-modified polybutadiene (3F-PBu-3F) was incorporated into natural rubber. Following sulfur curing, homogeneous phase morphologies were observed in all vulcanizates, which significantly differed from those of previously reported NR/polybutadiene vulcanizates. Additionally, the oil resistance and thermal stability of the NR/3F-PBu-3F vulcanizates were effectively enhanced. Full article

The growing interest in renewable resource-based materials has driven efforts to develop elastomeric biocomposites using biomass, phyto-ash, and biochar as fillers. These bio-additives, derived from beech wood through various processing methods, were incorporated into natural rubber (NR) at varying weight ratios. The primary objective of this study was to assess how the type and content of each bio-filler influence the structural, processing, and performance properties of the biocomposites. Mechanical properties, including tensile strength and hardness, were evaluated, while crosslink density of the vulcanizates was determined using equilibrium swelling in solvents. Additionally, the composites underwent thermogravimetric analysis (TGA) to determine the decomposition temperature of individual components within the polymer matrix. Bio-fillers influenced rheological and mechanical properties, with phyto-ash reducing viscosity and cross-linking density, and biochar and biomass increasing stiffness and maximum torque. Biochar extended curing time due to the absorption of curing agents, whereas phyto-ash accelerated vulcanization. Mechanical tests showed that all bio-filled composites were stiffer than the reference, with biochar and biomass (30 phr) exhibiting the highest hardness (45.8 °ShA and 49.1 °ShA, respectively) and cross-link density (2.68 × 10⁻⁵ mol/cm³ and 2.77 × 10⁻⁵ mol/cm³, respectively), contributing to improved tensile strength, in particular in the case of biochar, where the TS was 17.6 MPa. The study also examined the effects of thermal-oxidative aging on the samples, providing insights into the changes in the mechanical properties of the biocomposites under simulated aging conditions. Full article

Fumed silica, a nanomaterial with a high specific surface area, excellent chemical stability, and electrical insulation, serves as an effective filler for rubber compounding. Compared to traditional carbon black, silica (SiO₂), the main component of fumed silica, improves the hardness and tear resistance of tread rubber, making it a viable substitute in some formulations. However, silica-filled compounds generally exhibit lower tensile properties and abrasion resistance than carbon black. Fumed silica, with its higher structural integrity, provides additional reinforcement points within natural rubber matrices, enhancing tensile strength and abrasion resistance. Studies demonstrate that replacing carbon black with an equivalent amount of fumed silica as the primary filler significantly improves tread rubber’s hardness (by 20%) and 300% tensile modulus (by 14%) while also reducing rolling resistance and enhancing wet skid performance. Fumed silica’s large specific surface area and low density (10–15% of conventional silica) make it challenging to use directly as a tread rubber filler due to dust formation and prolonged mixing times. This study developed a process combining fumed silica with deionized water, followed by drying and ball milling. This treatment reduces the material’s volume, forming a cohesive gel that, upon processing, minimizes dust and significantly decreases mixing time and difficulty. The interaction between the hydroxyl (–OH) groups on the surface of fumed silica and water molecules likely results in hydrated silica. This interaction enhances surface polarity and forms a hydration layer, improving the hydrophilicity and dispersion of fumed silica in rubber matrices. This reduces the shear modulus difference (ΔG′) between low and high strain, maintaining a consistent elastic modulus over a wide strain range. Such stability enables rubber to perform better under dynamic loads or in complex working conditions. The experimental results demonstrate that the hydration–ball milling process enhances the tensile strength of vulcanizates, improves the dispersion of fumed silica in rubber, strengthens the filler network, boosts dynamic performance, and enhances the wet skid resistance of tread rubber. Full article

The damping performance of chlorinated butyl rubber (CIIR) is exceptional; however, its poor processability during vulcanization can lead to numerous defects. Natural rubber (NR) and ethylene propylene diene monomer rubber (EPDM) were selected to blend with CIIR for improving its processing performance. Their effects on the vulcanization characteristics, mechanical properties, and damping performance were investigated. Blending CIIR with NR can considerably increase the vulcanization speed of the rubber compound and improve production efficiency. The tensile strength of the vulcanizate first increases with an increase in the dosage of NR in NR/CIIR, and subsequently, it decreases before increasing again. The tensile strength first increases and then decreases with an increase in the EPDM dosage in EPDM/CIIR vulcanizate. The tensile strength increases by 15.6%when the EPDM dosage is 60 and 80 phr. EPDM and NR have similar effects on the damping performance of CIIR, which were evaluated by fitting the data of loss factor (∆tanδ) versus NR or EPDM dosage. Therefore, the quantity of NR or EPDM can be conveniently calculated based on performance requirements when designing the formula of the CIIR matrix materials. Full article