Diene Rubber Research Articles

Physicochemical properties and flame retardancy of irradiated EPDM nanocomposites and possible application as insulating materials

This work aims to develop a new kind of ethylene propylene diene rubber (EPDM) to be utilized as insulator in electrical cables. This type was incorporated with Al(OH)3, Al2O3, and graphene oxide (GO) to decrease the flammability of the rubber. Al2O3 nanoparticle was synthesized via Sol-Gel route. The produced nano Al2O3 powder was characterized using X-ray diffraction and FTIR absorption. The morphologies were studied using SEM and TEM. The characterization demonstrated that the particle size of the prepared Al2O3 a nano-spheres had an average diameter of 19–30 nm. Gamma radiation affected the mechanical, electrical, and thermal properties. The incorporated rubber consisted of homogenous nanoparticles. Additionally, the samples flammability was examined utilizing limited oxygen index (L.O.I) and the effect of γ- radiation on the flammability was investigated. The analysis of the obtained values reveals that the additive materials will be incorporated with rubber. Also, the influence of γ- radiation on the mechanical and thermal behavior indicates that a little positive effect accompanied the γ- radiation of the samples. The evaluation of the prepared samples as flame retardant for rubber indicate that the value of L.O.I = 20.5 for native rubber and increased to 27.1 for the composite EPDM/Al(OH)3/2%Al2O3/1% GO. This value candidates this composite to be used as insulator in the electrical cable because the addition of Al component and graphene restricted the spread of the flame and dispersed the smoke.

TPV concentrate: Fabrication and performance

Thermoplastic vulcanizates (TPVs) have been widely studied and applied in recent years because of their excellent elasticity and re-processibility similar to those of thermoplastics. However, its dynamical vulcanization processing normally requires an expensive twin-screw extruder with a very high L/D ratio. In this paper, a kind of thermoplastic vulcanizate concentrate (TPVC) with very high rubber phase content and low hardness was prepared by using highly oil-extended ultra-high molecular weight ethylene propylene diene rubber (EPDM) dynamically cured by peroxide and a low melt index polypropylene (PP) and extra oil softener. Then a new kind of high purity TPV with a wide hardness range was fabricated by using this TPVC simply melt blended with various contents of PP. The mechanical and recycling properties, rheological responses, phase morphology, crystallization, thermal stability and UV radiation resistance were systematically studied. In addition, because TPVC is filled with a large amount of white oil, the process parameters can be controlled reasonably by studying the distribution coefficient of white oil in the two phases.

STUDY OF THE INFLUENCE OF HDPE AND UHMWPE ON THE PROPERTIES OF ETHYLENE PROPYLENE DIENE VULCANIZATES

Introduction of small additives of thermoplastic polymer into the elastomer matrix is one of the simple and effective ways to improve the complex of physical and mechanical properties of rubbers. This article is devoted to the study of the effect of low-density polyethylene (HDPE) grade 273-83 and ultra-high molecular weight polyethylene (UHMWPE) grade GUR 4113 on the vulcanization characteristics of rubber compounds, physical and mechanical properties and resistance to thermal aging of vulcanizates based on ethylene propylene diene rubber grades SKEP-40 and SKEP-50. The use of HDPE and UHMWPE as additives is of interest not only due to their properties, but also due to their similar chemical nature to SKEP. It is shown that the introduction of polyethylene additives leads to some increase in the duration of the rubber compounds in the viscous flow state and the vulcanization optimum. Vulcanizates containing polyethylene additives are charac-terized by an increase in the conventional stress at 100 % elongation and a decrease in the relative elongation at break, which indicates an increase in the rigidity of the vulcanizates. In the presence of PE, wear resistance and the ability to elastic-elastic recovery of vulcanizates after compression also increase significantly. The frost resistance coefficient of rubber samples containing UHMWPE remains at the level of the original vulcanizates, and in the case of HDPE it decreases significantly, which can be explained by the better ability of UHMWPE to maintain its flexibility at low temperatures. According to the results of accelerated thermal aging, it was found that the presence of polyethylene additives leads to a significant increase in the stability of the elastic-strength properties of vulcanizates based on SKEP-50. Moreover, the higher the molecular weight of polyethylene, the higher its efficiency. It should be noted that in the DOT-4 environment, vulcanizates are characterized by a greater degree of preservation of elastic-strength indicators compared to the air environment, which is due to their high resistance to this working environment. It was found that UHMWPE, compared to HDPE, results in the production of an elastomeric material based on EPDM with a more optimal set of physical and mechanical properties and increased stability of elastic strength indicators after thermal aging.

Recycling devulcanized EPDM to improve engineering properties of SBR rubber compounds

Ethylene propylene diene rubbers (EPDM) have gained substantial attention in automotive and industrial applications owing to their exceptional resistance against weathering and heat. Despite their advantages, the elastomeric nature of EPDM poses challenges in its recycling due to the presence of crosslinks in their chemical structure, preventing them from melting. To overcome this issue, devulcanized EPDM (EPDMd) has been developed, characterized by the effective breaking of these crosslinks. Our study focuses on common composites that include Styrene Butadiene Rubber (SBR), EPDM and silica, but with the incorporation of devulcanized EPDM (EPDMd).We have studied the mechanical, thermal, structural and dielectric properties of SBR composites containing EPDMd at variable compositions (0, 20, 40, 50, 60 phr). Employing techniques such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectropy (FTIR), and Scanning Electronic Microscopy (SEM), we have explored the microstructural changes driving the macroscopic effects on the measured properties.The results show that incorporating EPDMd improves the crosslinking degree and, at optimal 40 phr loading, significantly increases the mechanical properties of SBR matrix. The addition of SiO2, in general, reduce tensile strength and elongation, while increasing the Young's modulus, except for compositions around 40 phr EPDMd. The dielectric measurements are in concordance with the previous data, showing a moderation of the Maxwell–Wagner–Sillars (MWS) effect due to SiO2 in highly filled EPDMd composites at 40 phr EPDMd.

Exploring Green Route of Cross-Linking for Bio-Based Ethylene Propylene Diene Rubber: A Step toward Circular Economy

Exploring Green Route of Cross-Linking for Bio-Based Ethylene Propylene Diene Rubber: A Step toward Circular Economy

The study on the micromechanical mechanism of PP/EPDM blends and PP/SEBS blends using atomic force microscopy-based nanomechanics

Using atomic force microscope-based nanomechanics to measure the micromechanical properties of different polymer blends, we found that the miscibility of the blend system affects the phase structure and micromechanical properties at the nanoscale, which further affects macroscopic mechanical properties of materials. In the immiscible polypropylene/ethylene propylene diene rubber blends, the microscopic phase structure is connected to the macroscopic mechanical properties of the material, since the microscopic modulus of elasticity of the phases remains constant even if the blend ratio is changed. On the other hand, in the partially miscible polypropylene/styrene-ethylene-butylene-styrene block copolymer blends, the macroscopic mechanical properties of the material are determined by the combination of the microscopic phase structure and the microscopic elastic modulus, because the microscopic elastic modulus of each phase changes with the blending ratio.

Synthesis of liquid EPDM having ultra-low-viscosity for curing at room temperature

A serial of liquid ethylene–propylene–diene rubber (EPDM) with 5-ethylidene-2-norbornene (ENB) contents of 2.0–6.5 mol% were synthesized by using VOCl3 based catalysts. The obtained polymers have much low molecular weight with Mn = 4530–10180 g/mol (PDI = 3.5–7.1), consequently, these EPDMs without solvent have excellent flowability with the viscosity of 2198∼7460 mPa s at 25 °C. And the glass transition temperature as low as −85.9 °C was achieved. Impressively, these liquid EPDMs can be cured at 25 °C after 5 days. NMR analysis suggested that ethyl trichloroacetate acted as activator to chlorinate V(II) species to V(III), but also acted as polymer modifier to provide a chlorinated EPDM, which appeared to be essential for liquid EPDMs curing at low temperature. The dynamic water contact angle results demonstrated that the EPDMs had excellent wettability properties and surface properties. Thus, this work provided a facile way for one-pot synthesis of liquid EPDM containing functional group for curing at room temperature.

The Synergistic Effect of Carbon Black/Carbon Nanotube Hybrid Fillers on the Physical and Mechanical Properties of EPDM Composites after Exposure to High-Pressure Hydrogen Gas.

This study investigated the synergistic effect of carbon black/multi-wall carbon nanotube (CB/MWCNT) hybrid fillers on the physical and mechanical properties of Ethylene propylene diene rubber (EPDM) composites after exposure to high-pressure hydrogen gas. The EPDM/CB/CNT hybrid composites were prepared by using the EPDM/MWCNT master batch (MB) with 10 phr CNTs to enhance the dispersion of CNTs in hybrid composites. The investigation included a detailed analysis of cure characteristics, crosslink density, Payne effect, mechanical properties, and hydrogen permeation properties. After exposure to 96.3 MPa hydrogen gas, the hydrogen uptake and the change in volume and mechanical properties of the composites were assessed. We found that as the MWCNT volume fraction in fillers increased, the crosslink density, filler-filler interaction, and modulus of hybrid composites increased. The hydrogen uptake and the solubility of the composites decreased with an increasing MWCNT volume fraction in fillers. Moreover, after exposure to hydrogen gas, the change in volume and mechanical properties exhibited a diminishing trend with a higher MWCNT volume fraction. We conclude that the hybridization of CB and CNTs formed strong filler-filler networks in hybrid composites, consequently reinforcing the EPDM composites and enhancing the barrier properties of hydrogen gas.

Enhancing electrical characteristics and electromagnetic interference shielding effectiveness in thermoplastic elastomeric polymer blends by utilizing the selective distribution of conductive black

The selective distribution of filler within polymer blends presents a compelling advantage, notably manifesting as a reduced percolation threshold when compared to an individual polymer matrix with a random filler dispersion. In this context, a thermoplastic elastomeric (TPE) blend comprising ethylene propylene diene rubber (EPDM) and linear low-density polyethylene (LLDPE), denoted as EL, has been meticulously formulated. The incorporation of varying amounts of conductive carbon black (Vulcan XC 72; VCB) into this TPE matrix has been achieved through conventional melt blending, yielding a composite material with exceptional electromagnetic interference (EMI) shielding effectiveness of -27.80 dB at 50 phr (parts per hundred rubber). This success is credited to the creation of a linked structure resulting from a dual-step percolation process. The selective distribution of carbon black (CB) throughout the TPE mixture results in a decreased critical concentration for connectivity and enhanced electromagnetic interference (EMI) shielding performance. This advancement underscores the potential of EPDM-LLDPE-VCB (ELV) composites to safeguard against electromagnetic radiation. It paves the way for their utilization in various techno-commercial applications, where a balance of mechanical strength, thermal stability, and flexibility is crucial.Graphical

Conventional and Green Rubber Plasticizers Classified through Nile Red [E(NR)] and Reichardt’s Polarity Scale [ET(30)

After a survey on polymer plasticization theories and conventional criteria to evaluate polymer–plasticizer compatibility through the solubility parameter, an attempt to create a polymer–plasticizer polarity scale through solvatochromic dyes has been made. Since Reichardt’s ET(30) dye is insoluble in rubber hydrocarbon polymers like polyisoprene, polybutadiene and styrene–butadiene copolymers and is not useful for the evaluation of the hydrocarbons and ester plasticizers, the Nile Red solvatochromic dye was instead used extensively and successfully for this class of compounds. A total of 53 different compounds were evaluated with the Nile Red dye and wherever possible also with Reichardt’s ET(33) dye. A very good correlation was then found between the Nile Red scale E(NR) and Reichardt’s ET(30) scale for this class of compounds focusing on diene rubbers and their typical hydrocarbons and new ester plasticizers. Furthermore, the E(NR) scale also shows a reasonable correlation with the total solubility parameter calculated according to the Van Krevelen method. Based on the above results, some conclusion was made about the compatibility between the diene rubbers and the conventional plasticizers, as well as a new and green plasticizer proposed for the rubber compounds.

Effect of interfacial sacrificial bonds on the vulcanization and mechanical properties of styrene butadiene rubber/talcum powder composites

AbstractTalcum powder (Talc) contains large amounts of silica; however, its poor surface compatibility with diene rubber makes it difficult to develop its application in styrene‐butadiene rubber (SBR). Herein, a method to enhance the compatibility of Talc with SBR via interfacial sacrificial bonds of 4‐vinylpyridine and Mg2+/Zn2+ is proposed. Poly(isoprene‐co‐4‐vinylpyridine) copolymers, designated PIPVP‐10 and PIPVP‐20, were synthesized via reversible addition‐fragmentation chain transfer polymerization. PM1‐Talc and PM2‐Talc were obtained by spraying PIPVP‐10 and PIPVP‐20 solutions onto the Talc surface, followed by drying. During thermal vulcanization, the double bonds in the copolymers can be grafted directly onto the rubber skeleton. The vulcanization rates of the SBR/PM1‐Talc and SBR/PM2‐Talc complexes were accelerated by 65% and 77%, respectively, compared with that of SBR/Talc. Simultaneously, the interfacial interaction between SBR and Talc is enhanced owing to the formation of metal–ligand bonds between pyridine and Mg2+/Zn2+. As a result, the tensile strengths of SBR/PM1‐Talc and SBR/PM2‐Talc are 5.8 and 7.9 MPa, 65% and 127% higher than that of SBR/Talc (3.5 MPa).

Vulcanization of styrene-butadiene rubber with the use of polysulfide sulfur-donors of controlled structure

The sulfide polymers of variable and controlled sulfur content, obtained by anionic copolymerization of elemental sulfur and thiiranes (styrene sulfide and cyclohexene sulfide), were applied as curatives (sulfur donors) in the vulcanization process of styrene-butadiene rubber (SBR). The activity of polysulfides as curatives was investigated on the basis of rheometric measurements of the vulcanization process and calculations of curing parameters using kinetic data. The crosslink density and structure related to the mechanical properties of the vulcanizates under static and dynamic conditions were studied. The overall suitability of polysulfides as crosslinking agents for diene rubbers was investigated.

МОДИФИКАЦИЯ РЕЗИН НА ОСНОВЕ ЭТИЛЕНПРОПИЛЕНДИЕНОВОГО КАУЧУКА СИЛОКСАНОВЫМ КАУЧУКОМ

Rubbers based on ethylene propylene diene rubber are widely used in the cable industry due to the possibility of using such rubbers in extreme conditions. However, such rubbers have limitations in heat resistance. To increase the heat resistance of such rubbers, it is possible to combine ethylene propylene diene with other rubbers. At the same time, it must be taken into account that the rubbers must be compatible with each other. To increase the heat resistance of rubbers based on ethylene propylene diene rubber, it is possible to introduce silicone rubber into the composition. Owing to the unique character of the main chain consisting of alternating atoms of silicon and oxygen, siloxane rubber-based rubbers have increased thermal and fire resistance, which makes them widely used for the production of items operating in high-temperature conditions. Ethylene propylene diene and silicone rubbers can be vulcanized with a common agent - organic peroxide. There are known works on improvement of frost resistance of rubbers based on ethylene propylene diene rubber by combining it with methylphenylsiloxane rubber. In this work the influence of SKTV-1 rubber content up to 50% wt. % on the properties of rubber based on EPDM is investigated. Vulcanization characteristics, physical and mechanical properties of rubbers before and after thermal aging, and electrical insulating properties were assessed. Thermal aging of rubber was carried out at temperatures of 130, 150 and 180 °C. It has been established that with a ratio of EPDM/SKTV rubbers of 90/10, it is possible to increase the heat-resistant properties of rubbers. For better combination of rubbers, a plasticizer based on siloxane rubber destructor was introduced in an amount of 5 parts by weight. The plasticizer makes it possible to increase the compatibility of rubbers and does not negatively affect the entire range of properties.

VULCANIZATION OF STYRENE–BUTADIENE RUBBER WITH THE USE OF POLYSULFIDE SULFUR DONORS OF CONTROLLED STRUCTURE

ABSTRACT The sulfide polymers of variable and controlled sulfur content, obtained by anionic copolymerization of elemental sulfur and thiiranes (styrene sulfide and cyclohexene sulfide), were applied as curatives (sulfur donors) in the vulcanization process of styrene–butadiene rubber. The activity of polysulfides as curatives was investigated based on rheometric measurements of the vulcanization process and calculations of curing parameters using kinetic data. The crosslink density and structure related to the mechanical properties of the vulcanizates under static and dynamic conditions were studied. The overall suitability of polysulfides as crosslinking agents for diene rubbers was investigated.

Anti-aging effect of TMQ on EPDM for Various Cure Systems

Ethylene propylene diene rubber (EPDM) is a common raw material for weather resistant rubber products used in lots of areas such as cable, automotive, marine industry and aviation applications. Superior processing behaviour, electrical properties and moderate high temperature resistance also make EPDM an attractive raw material for a wide range of further industrial performance requirements. As well as the other general purpose rubbers, EPDM needs to be protected against thermo-oxidative aging. Short and long term aging behaviour of both sulphur and peroxide cured EPDM has been studied in literature. However, to the authors’ best knowledge, there is not any study in literature systematically evaluating a common rubber antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) for investigating theoretical life-time of EPDM based materials that were vulcanized with different crosslinking systems. In this study, effects of TMQ on the thermo-oxidative resistance of EPDM has been studied for conven-tional and efficient sulphur vulcanization systems as well as peroxide vulcanization system. Aging mechanism for different cases has been investigated by using structural, rheological and mechanical tests. Thermo-oxidative aging has been monitored by carbonyl index and activation energy. Arrhenius based life-time estimation methodology has also been employed to evaluate aging behaviour of the reference and TMQ containing (-T) compounds. TMQ was found to exhibit different levels of protection against thermo-oxidative aging for all the curing systems and at all aging conditions. Higher aging activation energy for -T compounds has been attributed to extended service life of the material in the presence of TMQ.

Ultra-high molecular weight EPDM composites via crossover curing agents: Stabilized crosslink network structure and performance properties

This study investigates the impact of various crosslinking systems, such as those based on sulfur, peroxide, and their hybrid combinations, on the thermal degradation characteristics of ethylene propylene diene rubber (EPDM). During aerobic degradation, polymer networks undergo reversible physical and irreversible chemical changes. There are two kinds of irreversible chemical changes that may occur: chain scission reactions and crosslinking events. The impact of these reactions on the characteristics of the elastomer is antagonistic. When measuring the properties of an elastomer as it ages, most standard characterization techniques reveal the aggregate impact of two reactions. This work employs a straightforward approach based on compression set measurements to distinguish between the scission and crosslinking events that occur during thermal aging. This work has analyzed hybrid crosslinked materials using this method and demonstrated their remarkable thermal stability, as evidenced by their ability to maintain equilibrium between scission and crosslinking reactions. The stability of performance characteristics, such as tensile strength and crosslink density, in hybrid-cured samples during thermal aging supports the aforementioned. Furthermore, the investigation also delves into the potential of hybrid curing systems using crossover curing agents instead of coagents, which are multifunctional additives, to augment the durability of performance characteristics over an extended period of thermal aging.

Unraveling the ablative behavior through the design of a POSS-Benzoxazine/EPDM network under harsh environments

In order to meet the demands of the insulation layer in the swiftly advancing aerospace thermal protection system and enhance the ablation resistance of ethylene propylene diene rubber (EPDM) insulation layer, a novel EPDM ablation resistance composite was designed by integrating benzoxazine fine-tuned with octal (propyl glycidyl ether) polyhedral oligomeric silsesquioxane (BA-POSS) into the network structure of EPDM. The resulting composite exhibited a more densely cross-linked EPDM/BA-POSS network, consequently augmenting both the mechanical and ablation properties of the EPDM ablation resistance composite. The cross-linking density and tensile strength of EPDM/BA-POSS composite with 18 phr (parts per hundred rubber) BA-POSS increased by 78.4% and 30.7%, respectively, and the linear ablation rate significantly reduced by 47.7%, compared with EPDM composite without BA-POSS. Additionally, the ablation mechanism of EPDM/BA-POSS composites was elucidated through an investigation of the thermo-chemical transformation and analysis of the ablated carbon layer. This study contributes novel insights and methodologies for the future design of low-density rocket motor insulation compounds that offer cost efficiency, enhanced functionality, and wider applicability.

Adducts of Carbon Black with a Biosourced Janus Molecule for Elastomeric Composites with Lower Dissipation of Energy.

Elastomer composites with low hysteresis are of great importance for sustainable development, as they find application in billions of tires. For these composites, a filler such as silica, able to establish a chemical bond with the elastomer chains, is used, in spite of its technical drawbacks. In this work, a furnace carbon black (CB) functionalized with polar groups was used in replacement of silica, obtaining lower hysteresis. CBN326 was functionalized with 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP), and samples of CB/SP adducts were prepared with different SP content, ranging from four to seven parts per hundred carbon (phc). The entire process, from the synthesis of SP to the preparation of the CB/SP adduct, was characterized by a yield close to 80%. The functionalization did not alter the bulk structure of CB. Composites were prepared, based on diene rubbers-poly(1,4-cis-isoprene) from Hevea Brasiliensis and poly(1,4-cis-butadiene) in a first study and synthetic poly(1,4-cis-isoprene) in a second study-and were crosslinked with a sulfur-based system. A CB/silica hybrid filler system (30/35 parts) was used and the partial replacement (66% by volume) of silica with CB/SP was performed. The composites with CB/SP exhibited more efficient crosslinking, a lower Payne effect and higher dynamic rigidity, for all the SP content, with the effect of the functionalized CB consistently increasing the amount of SP. Lower hysteresis was obtained for the composites with CB/SP. A CB/SP adduct with approximately 6 phc of SP, used in place of silica, resulted in a reduction in ΔG'/G' of more than 10% and an increase in E' at 70 °C and in σ300 in tensile measurements of about 35% and 30%, respectively. The results of this work increase the degrees of freedom for preparing elastomer composites with low hysteresis, allowing for the use of either silica or CB as filler, with a potentially great impact on an industrial scale.

Composition and technology effect on the structure and properties of frost-resistant elastomeric materials based on blends of polar and nonpolar rubbers

Elastomeric materials for sealing devices operated in the Far North, including the Republic of Sakha (Yakutia), must be resistant to working environments and have frost and wear resistance with acceptable physical and mechanical properties. Some of the listed properties are mutually exclusive and are not always achievable in materials based on individual rubber. Thus, one promising method for sealing elastomeric materials is the use of rubber mixtures. In this study, model blends based on nitrile-butadiene (BNKS-18), butadiene (SKD), and isoprene (SKI-3) rubbers were studied. Nitrile butadiene rubber was chosen as the component of the mixture responsible for resistance to working environments, and diene rubbers (SKD and SKI-3) were chosen as the components responsible for frost resistance. The addition of SKI-3 also suppressed the crystallization of SKD butadiene rubber. An increase in the BNKS-18 content enhanced the physical and mechanical properties and resistance to wear and non-polar oils. A decrease in lowtemperature properties and resistance to polar oils was also observed. Additionally, studies of the structure of the obtained materials by atomic force microscopy were carried out, which proved the uniformity of the distribution of particles of the dispersed phase, the size of which did not exceed 1-5 μm. The optimal ratio of butadiene-nitrile to diene rubbers was 70:30 phr. At this ratio, the obtained elastomeric materials meet the requirements of sealing materials for operation in cold climates.

Characterization of airborne microplastics at different workplaces of the poly(ethylene:propylene:diene) (EPDM) rubber industry.

Microplastics (MPs) as an emerging air pollutant have received widespread attention, but research on airborne MPs at occupational sites is still limited, especially in the rubber industry. Hence, indoor air samples were collected from three production workshops and an office of a rubber factory producing automotive parts to analyze the characteristics of airborne MPs in different workplaces of this industry. We found MP contamination in all air samples from the rubber industry, and the airborne MPs at all sites mainly showed small-sized (< 100μm) and fragmented characteristics. The abundance and source of MPs at various locations is primarily related to the manufacturing process and raw materials of the workshop. The abundance of MPs in the air was higher in workplaces where production activities are involved than in office (360 ± 61 n/m3), of which the highest abundance of airborne MPs was in the post-processing workshop (559 ± 184 n/m3). In terms of types, a total of 40 polymer types were identified. The post-processing workshop has the largest proportion of injection-molded plastic ABS, the extrusion workshop has a greater proportion of EPDM rubber than the other locations, and the refining workshop has more MPs used as adhesives, such as aromatic hydrocarbon resin (AHCR).