Sulfur Vulcanization Research Articles

In situ EPR investigation of sulfur vulcanization mechanism and ageing process

The purpose of this investigation was to determine the nature of radicals present on Natural rubber and poly isoprene system. The qualification and quantification of radicals was made by using Electron Paramagnetic Resonance spectroscopy (EPR). The mechanism of vulcanization has been studied in order to understand the formation of organic radicals. This could give us indications as to the nature of the sulfur chains formed during the process. Thanks to the in situ EPR we were able to highlight the formation of radicals S3•− which quickly transforms into a stable carbon radical. We can therefore assume in this radical mechanism that the length of sulfur chains observed is 3 sulfur. Sulfur containing more than 3 atoms would be created following an ionic pathway. These results have led us, once the radicals formed have been stabilized, to study the phenomena of thermal aging by monitoring the nature and quantity of radicals formed over longer times. These results allowed us to show the existence of oxygen vacancies which are transient species linked to the presence of ZnO used as an activator of vulcanization.

Two-Layer Rubber-Based Composite Material and UHMWPE with High Wear Resistance.

The aim of the study is the development of two-layer materials based on ultra-high-molecular-weight polyethylene (UHMWPE) and isoprene rubber (IR) depending on the vulcanization accelerators (2-mercaptobenzothiazole (MBT), diphenylguanidine (DPG), and tetramethylthiuram disulfide (TMTD)). The article presents the study of the influence of these accelerators on the properties and structure of UHMWPE. It is shown that the use of accelerators to modify UHMWPE leads to an increase in tensile strength of 28–53%, a relative elongation at fracture of 7–23%, and wear resistance of three times compared to the original UHMWPE. It has been determined that the introduction of selected vulcanization accelerators into UHMWPE leads to an increase in adhesion between the polymer and rubber. The study of the interfacial boundary of a two-layer material with scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) showed that the structure is characterized by the presence of UHMWPE fibrils localized in the rubber material due to mechanical adhesion.

Properties of silica/natural rubber composite film and foam: Effects of silica content and sulfur vulcanization system

Properties of silica/natural rubber composite film and foam: Effects of silica content and sulfur vulcanization system

Characterization of synthetic turf rubber granule infill in Japan: Rubber additives and related compounds

We have conducted several studies with an overall goal of assessing the effects of rubber granules in synthetic turf on the health of athletes, other players, and children in Japan. As part of these studies, the investigation reported herein was aimed at analyzing the concentrations of rubber additives (vulcanization accelerators, antioxidants, and cross-linking agents) and related chemicals in 46 rubber infills prior to their use in synthetic turf fields in Japan. Of the 36 chemicals selected for targeted analysis, 26 were detected and quantified. Nontargeted analyses further identified and quantified 16 compounds derived from vulcanization accelerators, plasticizers, and other additives. The types and concentrations of the detected compounds varied both between products and within the same product; in the case of rubber infill products made from recycled rubber, this variation was caused by the different types of rubber products recycled as raw materials. Elution tests with four simulated biofluids (gastric juice, intestinal juice, saliva, and perspiration) revealed that the elution rates varied between compounds and were affected by the presence of coatings. Most compounds had low elution rates in all the simulated biofluids, with many at or below the limit of quantification. The data reported herein will be utilized in the risk characterization part of our subsequent study on the health risk assessment of rubber infill.

Inverse Vulcanization with SiO2-Embedded Elemental Sulfur for Superhydrophobic, Anticorrosion, and Antibacterial Coatings

Sulfur-rich polymers generated from the inverse vulcanization of elemental sulfur with unsaturated monomers have emerged as a family of organic polymers with unique functionalities and broad potential applications. First described in 2013, inverse vulcanization is still in its infancy regarding its fundamental development, property exploration of the resultant polymers, and practical utilizations. Herein, the robust properties of sulfur-rich composites generated by inverse vulcanization with SiO2-embedded elemental sulfur are revealed, furnishing superhydrophobicity with static water contact angles of up to 154.7 ± 1.8°, a high anticorrosive effect of 98.9% protection efficiency for Mg alloy in 3.5 wt % NaCl solution, and a good antibacterial performance against Escherichia coli (81%) and Staphylococcus aureus (75%). The resulted composite also shows excellent self-cleaning functionalities. This has not only expanded the properties/functionalities and applications of the sulfur-rich polymers resulting from inverse vulcanization but also provided low-cost alternatives to superhydrophobic coating materials for practical applications.

Boron removal by glucamine-functionalized inverse vulcanized sulfur polymer

Boron removal by novel sulfur-based boron selective adsorbent is herein reported. The sulfur-based polymer prepared by the inverse vulcanization of sulfur and 4-vinylbenzyl chloride (VBC) under optimized reaction conditions was used as a substrate and further functionalized by N-methyl-D-glucamine (NMDG) under optimized reaction conditions. Batch adsorption boron removal tests showed that a pH of 9 results in the highest adsorption capacity while an increase in the adsorbent dosage also showed a non-linear increase in the removal capacity. Acid and alkali regeneration of the used adsorbent showed 86% of its initial capacity after five cycles. The equilibrium isotherms of the adsorption were best fitted with the Redlich-Peterson model indicating that the boron adsorption obeys the principles of both monolayer and multilayer adsorption with a Langmuir maximum adsorption capacity of 7.186 mg/g. On the other hand, pseudo-second-order best fitted the adsorption kinetics meaning that chemisorption is the main controlling mechanism. The thermodynamic studies showed an endothermic spontaneous adsorption process with an increased randomness degree at the solid/liquid interface after the adsorption. The developed adsorbent is the first sulfur-rich polymer and selective boron adsorbent that can effectively reduce boron in water while also offering a considerably lower price due to utilizing the cheap and already available elemental sulfur.

Inverse Vulcanization of Elemental Sulfur with Natural Rosin to Prepare High Sulfur Content Polymers with Excellent Solubility and UV‐Blocking Performance

UV Protection Inverse vulcanization of elemental sulfur (S) with natural rosin (Ro) to synthesize high sulfur content Sx-Ro copolymer is presented in article number 2100854 by Li Zhou and co-workers. The Sx-Ro not only shows excellent solubility in low boiling point solvents, but also exhibits superior UV absorption capability in the whole UV region, so it can be utilized as an anti-UV agent to improve the UV-blocking performance of other polymers.

Synthesis of sustainable poly(S-Abietic-co-Pinene) through inverse vulcanization of Kurdica gum and used to fabricate durable and recyclable super-hydrophobic cotton wool filter: Oil-water separation application

The renewable and sustainable poly(S-Abietic-co-Pinene) with a high sulfur content was synthesized by inverse vulcanization of elemental sulfur and natural kurdica gum (extracted from the Pistacia atlantica tree). This hydrophobic polysulfide (KPS) is dip-coated on cotton wool to obtain a super-hydrophobic filter with a water contact angle of 165°. All polysulfide and coated filters are characterized by the FTIR, 13CNMR, TGA, SEM, X-ray map, EDX, and WCA. The 3-Aminopropyltriethoxysilan (APTES) reagent was used to enhance the adhesive forces between cotton and the KPS coating. The super-hydrophobic cotton-KPS wool filters were conducted for six bi-phasic oil-water separations. The high separation efficiencies and permeate fluxes as well as the 100% rejection of the aqueous phase are advantages of cotton-KPS wool filters. Also, no significant change was observed in the separation efficiency after 20 recycling numbers, implying the high durability and stability of the super-hydrophobic coating on the cotton-KPS filter. The use of renewable natural materials for the synthesis of novel polymers and the fabrication of robust super-hydrophobic filters for oil water separation can be based on green chemistry and sustainable development principles.

Polymer composite based on NBR rubber compounded with rubber waste functionalized with potassium oleate

Waste is a material that occurs as a result of a biological or technological process that can no longer be used as such. Recycling and reusing waste make it possible to contribute to environmental protection and, of course, to the protection of human health by eliminating toxins during waste incineration. The purpose of this paper is to process and characterize polymer composites based on NBR rubber (butadiene-co-acrylonitrile rubber) and rubber waste functionalized with potassium oleate in terms of rheological characteristics (to determine the optimal vulcanization time), Brabender diagrams and physico-mechanical properties in normal state and after accelerated ageing at 70°C, for 168 h (using elastomer-specific equipment). Functionalized rubber waste (with potassium oleate up to 20% at 60°C) is introduced into the mixture in proportions of 10; 20; 30; 50%. The polymeric composites based on butadiene-co-acrylonitrile elastomer and rubber waste (ground with a cryogenic mill at 10,000 rpm, at the size of 0.35 mm) were compounded on a mixer with a capacity of 350 cm3 according to the working recipes. The mixtures were supplemented with vulcanization activators and accelerators on an electric roller, resulting in formulations in the form of 4 mm thick sheets, which are then subjected to the relevant characterizations according to the standards in force for the footwear industry.

A Highly Durable Rubber-Derived Lithium-Conducting Elastomer for Lithium Metal Batteries.

Elastomers offer attractive advantages over classical solid‐state electrolytes in terms of ensuring stable interfacial contact and maintaining fatigue durability, but the low ionic conductivity obstructs their practical applications in long‐life lithium metal batteries. In this work, rubber‐derived lithium‐conducting elastomer has been developed via sulfur vulcanization of nitrile butadiene rubber with a polymerizable ionic liquid to provide both high resilience and dramatically improved ionic conductivity. Owing to the chemically crosslinked network between rubber chains and ionic liquid fragments generated during vulcanization, the elastic lithium‐conductor achieves high resilience of 0.92 MJ m−3, superior cyclic durability of 1000 cycles at 50% strain, and high room‐temperature ionic conductivity of 2.7 × 10−4 S cm−1. Consequently, the corresponding solid‐state lithium/LiFePO4 battery exhibits a high capacity of ≈146 mAh g−1 with a high capacity retention of 94.3% for up to 300 cycles.

Newsprint microcrystalline fibers activated by different coupling agents and electron beam irradiation as filler for styrene-butadiene rubber-based composites

Natural fiber-reinforced polymer composites offer many benefits over predictable composite materials, such as accessibility, low-cost, lightweight, and high definite mechanical properties. However, the applications of these materials are quiet restricted due to the contests in realizing a good interface between the fibers and matrix. This is highly influenced by the fiber surface characteristics and the polymer matrix properties. Therefore, this work discusses the incorporation of newsprint microcrystalline fibers (NPMCFs) in styrene-butadiene rubber (SBR) based composite. The fibers were first treated with (consistent concentration (10 w/100 w) coupling agents to fiber, respectively. The coupling agents namely: vinyl acetate versatic ester (VAcVe), maleic anhydride (MA), and phenol-formaldehyde resin (PFR), followed by surficial modification by irradiation with 30 kGy electron beam. Pristine and produced fibers were compounded to SBR. Mixing the ingredients was carried out on a rubber roll mill and then molded on a hot press to induce sulfur vulcanization. Characterization of the yielded fibers was investigated using Fourier Transform Infrared Spectrometry (FTIR). The mechanical properties of composites, such as tensile strength (TS), tensile modulus, tensile set, and crosslinking density demonstrated enhanced values as a result of enforcing the SBR matrix. The morphological examination via scanning electron microscopy (SEM) techniques explicitly indicated the adhesion of the prepared fibers to SBR moiety. Thermogravimetric analysis (TGA) confirmed a remarkable improvement in the thermal stability of the developed MA and PFR/SBR composites.

Synthetic Rubber with the Tensile Strength of Natural Rubber

The preparation of synthetic rubber with tensile strength identical to that of natural rubber is a long-standing unsolved problem in chemistry despite extensive related research. Here, we prepare synthetic rubber with tensile strength identical to that of natural rubber as a result of our discovery that natural rubber is a naturally occurring nanocomposite with proteins and lipids. The synthetic rubber is prepared by chemically attaching nanoparticles onto microparticles of synthetic cis-1,4-polyisoprene dispersed in water as a colloidal dispersion, followed by drying to form an “island-nanomatrix structure” similar to that of natural rubber. The stress at break of synthetic cis-1,4-polyisoprene increases dramatically from 0.1 to 3.9 MPa. The cis-1,4-polyisoprene with an island-nanomatrix structure exhibits almost the same mechanical properties as natural rubber. In addition, the synthetic cis-1,4-polyisoprene with an island-nanomatrix structure is vulcanized in the conventional manner using sulfur, zinc oxide, a vulcanization accelerator, and stearic acid at 150 °C and 15 MPa for an optimal vulcanization time after mechanical mixing. The stress at break of the resulting vulcanized cis-1,4-polyisoprene with an island-nanomatrix structure is 35.2 MPa, which is higher than that of vulcanized natural rubber. The preparation of synthetic rubber with mechanical properties identical to those of natural rubber is achieved by the formation of an island-nanomatrix structure in the synthetic rubber and is demonstrated by the mechanical properties of the vulcanized synthetic rubber being identical to those of vulcanized natural rubber.

Improving reinforcement of natural rubber latex by introducing poly‐zinc dimethacrylate and sulfur vulcanizing system

AbstractIn this work, zinc dimethacrylate (ZDMA) was employed to reinforce natural rubber latex (NRL) and a new process was introduced. Polymethacrylic acid was prepared by emulsion polymerization of methacrylic acid (MAA), then mixed with ZnO in a different mole ratio (ZnO/MAA) and the mixture was noted as PZDMA. It was added to NRL and a traditional sulfur vulcanizing system was adopted simultaneously. The mechanical test results show that compared with the sample “NR,” the tensile and tear strength are significantly improved by the addition of PZDMA. When 7 phr ZnO (NR‐7A) are loaded, it can reach 25.1 MPa and 62.8 N/mm, which are higher than “NR” by 52.0% and 104.6%, respectively. While the strength of the NRL film reinforced only with PZDMA is quite limited. Detailed analysis by Fourier‐transforms infrared spectroscopy, X‐ray diffractometers, scanning electron microscopy, thermogravimetric, and dynamic mechanical analysis revealed that PZDMA is successfully formed and dispersed uniformly in NRL, PZDMA acts as a nanoparticle and ionic cross‐linking agent, and the covalent cross‐linking network is formed by a sulfur vulcanizing agent. The dual cross‐linking network shows a synergistic effect on the reinforcement of NRL. The present work provides a process to reinforce NRL with adjustable mechanical properties.

Study of the Effect of Silica Filler Silica 1165 on the Properties of Rubber for Rail Fastening Gaskets

The effect of silica filler Silica 1165 instead of kaolin and carbon black N220 on the plasto-elastic, rheometric, physical-mechanical, operational and dynamic properties of rubber based on general-purpose caoutchoucs was investigated in order to develop effective noise and vibration-absorbing rubber gaskets of rail fasteners for railway tracks. It has been established that the developed rubber with a sulfur vulcanizing system based on SKMS-30ARK, SKI-3 и SKD caoutchoucs with Silica 1165 additives has improved plasto-elastic and rheometric indicators, satisfactory physical and mechanical properties, is characterized by an increase in the vibration-absorbing properties of rubber, which is the determining factor for under-rail pads

Investigation of Rheological and Mechanical Properties of Rubbers Produced by Sulfur Vulcanization from EPDM Rubbers with Different Ethylene Ratios

In this study, the effect of ethylene on the rheological and mechanical properties of rubbers was investigated. For this purpose, rubbers were produced by mixing EPDM rubbers containing ethylene in different ratios and curing with sulfur. The formulations were modified so that all samples had the same hardness. Rheometer analysis results revealed that the flow consistency of the Suprene 512 F sample was higher than the other two samples. The curing time of 90% of the sample was later than the other two samples. As a result of the tensile-elongation analysis, it was observed that the Ts/MPa and Eb/% ratios of Suprene 512 F rubber with the highest ethylene content were substantially higher. The hardness analysis revealed that the increase in the amount of ethylene in the rubber was directly proportional to the increase in the tensile breaking strength. In addition, it was observed that the ethylene ratio in rubber linearly affected the hardness change after vulcanization. While making rubber blend formulations, it should be considered that the ethylene ratio in the mixture will directly affect the change in the hardness of the product formed as a result of vulcanization.

The Synergistic Effect of Dibenzyldithiocarbamate Based Accelerator on the Vulcanization and Performance of the Silica-Filled Styrene-Butadiene Elastomer.

This work focused on studying the effect of dibenzyldithocarbamate vulcanization accelerator on the curing characteristics and performance of styrene–butadiene elastomer (SBR) filled with nanosized silica. A dibenzyldithocarbamate derivative was applied as an additional accelerator to enhance the efficiency and the rate of sulfur vulcanization in the presence of two other accelerators, i.e., N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and/or 1,3-diphenylguanidine (DPG). Furthermore, the possibility of reducing the amount of zinc oxide (ZnO) and the elimination of CBS and DPG from elastomer compounds using dibenzyldithiocarbamate accelerator was tested. Dibenzyldithocarbamate derivative applied with other accelerators (especially CBS) effectively enhances the efficiency of SBR vulcanization by reducing the optimal vulcanization time and increasing the crosslink density of the vulcanizates despite the lower amount of ZnO. Moreover, vulcanizates with dibenzyldithocarbamate demonstrate higher tensile strength while having a smaller content of CBS or DPG compared to the reference SBR composites. Thus, the synergistic effect of dibenzydithiocarbamate derivative on the vulcanization and performance of SBR was confirmed. Furthermore, dibenzyldithocarbamate derivative enables the amount of ZnO to be reduced by 40% without harmful influence on the crosslink density and performance of the vulcanizates. Finally, it is possible to replace CBS with a dibenzyldithiocarbamate derivative without the crosslink density and tensile strength of the vulcanizates being adversely affected, while improving their resistance to thermo-oxidative aging.

The Versatility in the Applications of Dithiocarbamates.

Dithiocarbamate ligands have the ability to form stable complexes with transition metals, and this chelating ability has been utilized in numerous applications. The complexes have also been used to synthesize other useful compounds. Here, the up-to-date applications of dithiocarbamate ligands and complexes are extensively discussed. Some of these are their use as enzyme inhibitor and treatment of HIV and other diseases. The application as anticancer, antimicrobial, medical imaging and anti-inflammatory agents is examined. Moreover, the application in the industry as vulcanization accelerator, froth flotation collector, antifouling, coatings, lubricant additives and sensors is discussed. The various ways in which they have been employed in synthesis of other compounds are highlighted. Finally, the agricultural uses and remediation of heavy metals via dithiocarbamate compounds are comprehensively discussed.

DEPENDENCE OF THE PROPERTIES OF SULFUR AND PEROXIDE VOLCANISES BASED ON A MIXTURE OF ISOPRENE WITH POLYVINYL ACETATE ON THE STRUCTURE OF THE VOLCANIZATION NETWORK

The effect on the crosslinking process of modified isoprene rubber (SKI-3-PVA) with the participation of sulfur and dicumyl peroxide (PD) in the presence of hexachloroparaxylene (HCPA) and 2,4-dichloro-6-dimethyl-amino sym triazine was studied. It was found that, depending on the length of time, the number of crosslinks in these systems (SKN-3-PVA + sulfur + GHPK + ZnO; SKI-3-PVA + PD + GHPK) is 2.5x105 and 1.9x105 mol / cm³, respectively, per Based on the observed changes in the parameter of the spatial grid of the crosslinked samples, the yield of effective crosslinks was calculated. It was shown that in the presence of dicumyl peroxide in filled systems, the number of crosslinks decreases, and a decrease in crosslinks is also observed. Comparative tests of elastomeric materials based on SKI-3 - PVA copolymers in liquid aggressive media were carried out. Sol-gel analysis found that with an increase in the content of the copolymer in isoprene, the concentration of the number of cross-linked molecules in the copolymer increases. It is shown that the physical and mechanical properties of filled vulcanizates are inferior to sulfuric ones in strength properties, but surpass peroxide ones in thermal aging and the action of solvents. It was found that an increase in aging with an increase in the heating time of the samples indicates the formation of additional cross-links. The role of zinc oxide in the peroxide crosslinking of the SKI-3 - PVA copolymer has been studied. It was found that the introduction of zinc oxide has a noticeable effect on the rate of sulfur and peroxide crosslinking of mixtures based on SKI-3 - PVA copolymers, an increase in the structuring time of mixtures, destructive processes are observed, and the number of crosslinks and crosslinks decreases. It was found that the physical and mechanical properties of peroxide vulcanizates are inferior to sulfuric ones in strength properties, but they are superior to peroxide ones in thermal aging. It is shown that an increase in the resistance to aging with an increase in the heating time of the samples indicates the formation of additional cross-links. As a result of the reaction with oxygen and the accumulation of interacting polar groups. A decrease in the degree of swelling is associated with the formation of C-C chemical bonds in elastomers, it effectively participates in the formation of cross-links during peroxide vulcanization. The nature of the interaction of sulfur PD, HCPC, and DCDEAST with elastomers was judged by the change in the conditional number of crosslinks (n´c) and the number of crosslinked molecules (1 \ Ms) in unfilled sulfur and peroxide vulcanizates. It is shown that in sulfur peroxide mixtures based on SKI-3-PVA with the proposed agents at room temperature it causes the formation of effective crosslinks, and with an increase in the duration of heating in systems 1, 2, the number of crosslinked molecules increases. An increase in resistance to aging with an increase in the heating time of the samples indicates the formation of additional cross-links as a result of the reaction with oxygen and the accumulation of interacting polar groups. A decrease in the degree of swelling is associated with the formation of C - C chemical bonds in elastomers, effectively participating in the formation of a network of crosslinks during peroxide vulcanization. Thus, the analysis of the results of the studies performed allows us to conclude that elastomers based on the isoprene copolymer SKI-3-PVA obtained with the participation of vulcanizing agents of sulfur and peroxide (PD) in the presence of hexachloroparaxylene (HCP) and triazine compounds are superior to those known in terms of thermal stability. aging in strength and accumulation of permanent deformation in aggressive environments. Keywords: isoprene, polyvinyl acetate, hexachloroparaxylene, peroxide dicumil, vulcanization, modification

Effect of lanthanum cerium methionine on the properties of natural rubber

Lanthanum cerium methionine was synthesized using the metathesis method and its molecular formula was confirmed as La0.35Ce0.65Cl3(C5H10NO2S)3·2H2O via Inductively Coupled Plasma Optical Emission Spectrometer, FTIR, and thermogravimetry-differential scanning calorimetry characterization methods. Lanthanum cerium methionine can significantly reduce the activation energy of the vulcanization reaction. The vulcanization kinetics model is used to fit the vulcanization curve of the rubber, and the obtained vulcanization activation energy of lanthanum cerium methionine for rubber is E1 = 76.89 KJ/mol, E2 = 102.36 KJ/mol and E3 = 126.00 KJ/mol. The above value is lower than pristine rubber. The Kissinger method and Flynn–Wall–Ozawa method were used to analyze the activation energy of thermal-oxidative degradation of vulcanized rubber. It was found that the rubber added with lanthanum cerium methionine exhibited higher thermal-oxidative degradation activation energy compared to that of pristine rubber; in addition, it was more difficult to age under the same environment. These results indicated that lanthanum cerium methionine can be not only used as a vulcanization accelerator, but also plays a role in resisting thermal and oxygen aging.

Inverse Vulcanization of Elemental Sulfur with Natural Rosin to Prepare High Sulfur Content Polymers with Excellent Solubility and UV‐Blocking Performance

AbstractInverse vulcanization of cheap elemental sulfur (S) to prepare polymers that simultaneously possess high sulfur content and good solubility is still in its infancy. In this paper, the authors report the synthesis of a novel S‐rosin (Ro) copolymer (Sx‐Ro) based on the inverse vulcanization of S with natural Ro. The sulfur content of Sx‐Ro can be regulated in a wide range, while Sx‐Ro still presents excellent solubility in low boiling point solvents at high sulfur content. Even if the sulfur content in Sx‐Ro is as high as 50%, its solubility in tetrahydrofuran (THF) can still reach 26 mg mL−1. Moreover, the Sx‐Ro exhibits excellent ultraviolet (UV) absorption capability in the entire UV region (200–400 nm) and can be utilized as an effective anti‐UV agent to enhance the UV‐blocking performance of other polymers (e.g., polymethyl methacrylate [PMMA] and polystyrene [PS]) without compromise of transparency and thermal stability. Considering the fine solubility and superior UV‐blocking properties of Sx‐Ro, this work not only provides a versatile and effective anti‐UV material but also opens new opportunities for value‐added utilization of abundant S and Ro resources.