Vulcanization Research Articles

Effective natural rubber vulcanization using electron beam irradiation and DFT driven cross-linking agents

This study explores an eco-friendly and efficient method for vulcanizing natural rubber latex using electron beam irradiation, enhanced by cross-linking agents. Unlike conventional sulfur vulcanization, electron beam vulcanization can occur at room temperature, reducing the need for chemical additives and eliminating toxic waste. Both experimental and theoretical studies were performed to evaluate vulcanization efficiency, utilizing ethylene glycol dimethacrylate (EDMA) and 1,6-hexanediol diacrylate (HDDA) as cross-linking agents. Electron beam irradiation is an effective method for generating reactive radical species via homolytic cleavage of covalent bonds in natural rubber. Quantum mechanical calculations, including density functional theory (DFT) and transition state searches using linear and quadratic synchronous transit methods, were employed to examine molecular structures, energies, and reaction pathways in the vulcanization process. The findings reveal that HDDA demonstrates superior cross-linking performance compared to EDMA, making it the preferred choice for enhancing vulcanization efficiency. These results offer valuable insights for optimizing rubber manufacturing processes, potentially improving the quality and efficiency of industrial rubber production.

Effect of Pretreated CZ/S on the Vulcanization and Rheological Behaviors of Isoprene Rubber Vulcanizates

Effect of Pretreated CZ/S on the Vulcanization and Rheological Behaviors of Isoprene Rubber Vulcanizates

Biomimetic design of elastomers with improved mechanical properties by integrating hydrogen bonds with covalent crosslinking bonds

It is an important issue for rubber to realize reinforcement and expand application gallery in material science and engineering. In the present work, we initiated a bioinspired design to introduce sacrificial hydrogen bonds by post-modifying sulfur crosslinked carboxyl nitrile rubber with pendent urazole through triazolinedione “click” chemistry. The post-modification of the crosslinked rubber can not only avoid adverse effect of the grafted urazoles on rubber vulcanization, but also enable to evaluate the effect of sacrificial hydrogen bonds on the rubber based on a consistent covalent network. Under external stress, the hydrogen bonds between the urazoles can function as sacrificial bonds that would rupture prior to covalent bonds, during which enormous energy is dissipated and meanwhile facilitates the rubber chain orientation. In light of the unique energy dissipating mechanism, the modulus, ultimate stress, and toughness of the hydrogen bonds and sulfur bonds dual-crosslinked rubber material are improved simultaneously without sacrificing the stretchability, and these properties can be easily manipulated by varying the grafting ratio of urazoles.

Study of Styrene Butadiene Rubber Reinforced by Polybutadiene Liquid Rubber-Modified Silica.

The dispersion of silica in rubber systems and its interaction with rubber are two key factors in the preparation of rubber composites with excellent properties. In view of this, silica modified with terminal isocyanate-based polybutadiene liquid rubber (ITPB) is used to improve the dispersion effect of silica in rubber and enhance its interaction with the rubber matrix to improve the rubber's performance. The impact of different modification conditions on the dispersion of silica and the properties of modified silica-filled rubber composites were studied by changing the amount of ITPB and the modification method of silica, including blending and chemical grafting. The experimental results show that ITPB is successfully grafted onto silica, and the use of modified silica improves the cross-linking density of rubber, promotes the rate of rubber vulcanization, and overcomes the shortcomings of the delayed vulcanization of silica itself. When the ratio of ITPB liquid rubber to silica equals 1:20, the comprehensive performance of rubber is the best, the ITPB-modified silica has a better dispersion effect in rubber, and the rolling resistance is slightly improved, with tensile strength reaching 12.6 MPa. The material demonstrates excellent overall performance and holds promise for applications in the rail, automotive, and electrical fields.

Cross-reactivity between thiuram disulfides and dithiocarbamates. A study of TETD and ZDEC using mouse models.

Rubber accelerators are used in the vulcanization of rubber. However, rubber accelerators for example tetraethylthiuram disulfide (TETD) and zinc diethyldithiocarbamate (ZDEC) may cause contact allergy. Concomitant reactions between ZDEC and TETD have been observed in patients which could be explained by co- or cross-reactivity. To investigate cross-reactivity between TETD and ZDEC and vice versa. Groups of mice were sensitized with TETD or ZDEC based on reported EC3-values. Proliferation of lymphocytes were measured on day 5. To test cross-reactivity, mice were sensitized and challenged 3 weeks later with TETD or ZDEC. The inflammatory response was measured by changes in ear thickness and the proliferative response in CD4+ and CD8+ T cells in the submandibular and cervical draining lymph nodes. Sensitization of mice with doses of ZDEC 3%, TETD 5.6% or TETD 16.2% induced significant increased ear thickness and proliferation of CD4+ and CD8+ T cells. Challenge with ZDEC or TETD in these groups induced significant increased ear thickness. Challenge with ZDEC in mice sensitized to TETD 5.6% or TETD 16.2% induced significant increased proliferation of CD4+ and CD8+ T cells. We show cross-reactivity between TETD and ZDEC. Patients sensitized to TETD or ZDEC should avoid exposure to both ZDEC and TETD.

Green and energy-saving tread rubber by constructing chemical cross-linking interface between graphene oxide and natural rubber

The dispersibility of fillers and interfacial interaction are crucial for polymer nanocomposites. Developing a simple, efficient and green method to simultaneously reduce and functionalize graphene oxide (GO) for preparing graphene/rubber composites with excellent dispersibility and enhanced interfacial interactions remains one of the main trends in developing and expanding the application of graphene in the rubber industry. In this work, VOC (volatile organic compound) -free and environmentally friendly L-methionine (L-Met) was selected as the functional modifier of GO. Then, L-Met-modified GO (MGO) was blended with natural rubber (NR) in an aqueous phase to prepare MGO/NR composites. The amphiphilic property of L-Met not only reduced GO but also endowed it with less agglomeration and excellent water dispersibility, which was a prerequisite for achieving uniform dispersion of GO in the NR matrix. In addition, the amino acids on the surface of MGO enhanced the compatibility between GO and the protein-phospholipid layer on the outer layer of NR latex particles. Meanwhile, L-Met containing sulfur bonds promoted rubber vulcanization, resulting in the formation of a cross-linked network between the modified GO and NR molecular chains. Compared to unmodified GO/NR composites, MGO/NR composites exhibited excellent mechanical properties and low heat build-up. More importantly, the solid tire prepared by using L-Met as the interface modifier for GO filled rubber showed lower rolling resistance and temperature rise, and the energy saving efficiency was improved. This strategy is expected to provide a new insight into the green production of organically modified graphene and the preparation of low-energy-consumption green graphene tires.

N-[(1RS)-Camphan-2-ylidene]-4-ethoxyaniline and its reduction product as stabilizers of nitrile butadiene rubbers

Objectives. To investigate the protective efficacy of unreduced and reduced forms of the condensation product of D,L-camphor and p-ethoxyaniline in nitrile butadiene rubber formulations when compared with the conventional stabilizer N-isopropyl-N′-phenyl- p-phenylenediamine aged under laboratory and in situ climatic conditions in the tropics.Methods. The thermostabilizing effect of the condensation product of D,L-camphor and p-ethoxyaniline was evaluated by means of infrared spectroscopy using the dynamics of changes in the absorption bands of carbonyl and hydroxyl groups. The features of rubber vulcanization were studied by means of rotorless rheometry. Changes in the physical and mechanical properties of rubbers and degree of cross-linking were evaluated after thermo-oxidative aging in laboratory conditions. They also took into account the results of longterm exposure of samples in undeformed and deformed state in a tropical climate, taking into account meteorological data of the Can Gio climatic testing station.Results. It was found for the first time that condensation products of D,L-camphor and p-ethoxyaniline exhibit a stabilizing effect in formulations of rubbers based on polar nitrile butadiene rubber.Conclusions. According to the results of laboratory and in situ tests, the study established that the use of N-[(1RS,2RS)-camphan-2-yl]- 4-ethoxyaniline (reduced form) as an antifatigue agent is preferable. This is due to the presence of a mobile hydrogen atom at the nitrogen atom. The protective effect is manifested in terms of the better preservation of elastic-strength properties of rubbers with less change in hardness.

TREATMENT FOR REMOVING ZN COMPOUNDS FROM SILICA-FILLED VULCANIZED RUBBER AND ANALYSIS OF SILICA AGGREGATE DISPERSION

ABSTRACT Treatment of silica-filled rubber vulcanizates with a diethyl ether/concentrated hydrochloric acid solution for 96 h at room temperature can remove most Zn compounds smaller than approximately 90 nm, which account for most of the residual ZnO, rubber-soluble Zn compounds and ZnS resulting from crosslinking reactions of by-products. However, a very small number of giant ZnO particles of a few micrometers in size remain after such treatment. In the silica-filled SBR matrix treated for 96 h, a significant increase in crosslink density and Young’s modulus was observed due to crosslinking reactions after HCl was removed from HCl-added rubber molecules. This increase in crosslink density was accompanied by an increase in the surrounding layer of bound rubber closest to the silica of the two bound rubber layers around it and a decrease in the rubber matrix of the same volume. It is inferred that there was little change in the aggregate structure of the silica due to these volume changes. Alternatively, ultra-small X-ray scattering measurements of the treated samples showed shoulders derived from silica aggregates and clear high-resolution X-ray computed microtomography (X-ray CT) images were obtained due to the removal of Zn compounds smaller than approximately 90 nm in size. The relationship between these shoulders and the size of silica aggregates obtained by X-ray CT imaging was qualitatively consistent, and it was not affected by the presence or absence of bis-(3-triethoxysilylpropyl) tetrasulfide and 1,3-diphenylguanidine, but was dependent on the rubber type. The distance between nearest neighbor particles of silica aggregates, determined by X-ray CT imaging, also depended on the types of rubber.

Adverse effect of TWPs on soil fungi and the contribution of benzothiazole rubber additives

Tire wear particles (TWPs) pollution is widely present in soil, especially in areas severely affected by traffic. Herein, regular variation of fungal biomass with TWPs was found in soils with different distances from the highway. In addition, the concentrations of benzothiazole compounds (BTHs), an important class of rubber vulcanization accelerators, were found to be positively correlated to the TWPs abundance. Sixty days' soil microcosm experiments were conducted to further confirm the adverse effect of TWPs and BTHs on soil fungi. TWPs spiking at 1000 mg/kg, a detectable level in the roadside, resulted in significant reduction of biomass and significant changes of soil fungal community structure, with Eurotium and Polyporales being the sensitive species. BTH+ 2-hydroxybenzothiazole (OHBT) (the dominant BTHs in soil) spiking at 200 ng/kg, the dose equivalent to 1000 mg/kg TWPs pollution, also caused a similar magnitude of soil fungal biomass reduction. Adonis demonstrated no significant difference of fungal community structure between TWPs and BTH+OHBT spiked soil, suggesting the adverse effect of TWPs on soil fungi may be explained by the act of BTHs. Pure culture using the representative soil fungi Eurotium and Polyporales also confirmed that BTHs were the main contributors to the adverse effect of TWPs on soil fungi.

Utilization of spent bleaching earth as green filler and plasticizer in the manufacture of rubber compounds for solid tire production

This study utilized spent bleaching earth (SBE) as a single form of filler and plasticizer in the manufacture of rubber components for solid tire vulcanizate. SBE, an underutilized byproduct of vegetable oil purification, is abundantly available globally and can be used as a filler and plasticizer in rubber compounds. This aligns with environmental sustainability principles, reduces disposal costs, and lowers raw material expenses in rubber manufacturing. In this research, the SBE was applied for each formula from SBE-02 to SBE-05 at ratios of 15–30 per hundred rubber (phr). As a comparison, carbon black (CB) filler (65 phr), CaCO3 (35 phr), and plasticizer derived from petroleum in the form of paraffinic oil (PO) (6 phr) were used. Rubber components were produced by masticating natural and synthetic rubber in an open mill, followed by the addition of filler, plasticizer, accelerator, co-activator, anti-degradant, and vulcanization agent. The resulting compounds were vulcanized at 150 °C and 10 MPa for 17 minutes. The test results demonstrated that incorporating SBE at a ratio of 15 phr (SBE-02) significantly reduced the cure time (t90) to 8 minutes and 20 seconds, the shortest among all tested formulations. The mechanical properties of the SBE-02 vulcanizate rubber met the requirements for solid wheelchair tire applications, with a hardness of 70 Shore A. However, its abrasion resistance test result of 189.1 g/cm³ was the lowest among the formulations tested. Furthermore, the scorch time (ts2) of the SBE-02 was determined to be 2 minutes and 35 seconds. Results from a 1000x magnification scanning electron microscope (SEM) reveal air gaps on all sample surfaces of different sizes. The elements C, O, Zn, Si, Ca, and Pb dominate the SEM-EDX results for all rubber vulcanizate samples from all three spectra, in varying weight percentages. The identification of functional groups with FTIR on all rubber vulcanizate samples shows Si–O–Si bending at 2, 4, and 5 and Si–O–Al stretching at 3, 5 on the wave number spectrum of 680–413 cm−1 Si–O–Si on the wave number spectrum 1100–1050 cm−1 from the infrared spectrum.

Tracing the odor source of crumb rubber modified asphalt emissions and evaluating the deodorization effect of attapulgite

Crumb rubber modified asphalt (CRMA) is widely used in road construction due to its excellent performance. However, it generates significant odorous gases during paving. To analyze the odor contribution, both untreated crumb rubber and desulfurized rubber were involved in this study to prepare CRMA and desulfurized rubber modified asphalt (DRMA). Attapulgite was selected as an emission reduction agent to reduce the odorous emissions released from CRMA and DRMA. An indoor fume collection system and gas chromatography-mass spectrometry (GC-MS) analysis were used to trace the odor source and quantify the odorous emissions. A comprehensive olfactory thresholds database for CRMA emissions was further established to evaluate the odor level of various rubberized asphalt binders by using three-point comparative odor bag method, along with known olfactory thresholds of certain compounds reported in the literature. Dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), bending beam rheometer (BBR) and Brookfield viscosity tests were used to analyze the effect of attapulgite on rheological properties of CRMA and DRMA. Results indicated that odor emission rate of CRMA containing 1 %, 3 %, and 5 % attapulgite was decreased by 42.62 %, 63.29 %, and 71.06 %, respectively. Benzothiazole, derived from tire rubber vulcanization accelerator, can be reduced by 60.25 % with 1 % attapulgite, demonstrating excellent performance in terms of reducing target odor emissions. Although DRMA has a lower emission rate than that of conventional CRMA, the addition of 1 % attapulgite can further reduce the odor emission rate of DRMA by 37.92 %. The addition of attapulgite has less impact on the overall performance of CRMA and DRMA. Besides, it was found that attapulgite can reduce the viscosity of rubberized asphalt binders, which is beneficial for rubberized asphalt mixture paving and compaction. Considering odor reduction, performance, and economic factors, the optimal attapulgite content was determined to be 5 % for CRMA and 1 % for DRMA. This approach successfully reduces odorous emissions while maintaining the desirable properties of CRMA, making it a viable solution for environmentally friendly road construction.

Evaluation of Enhanced Mechanical Properties in Natural Rubber Hybrid Reinforced with Industrial Waste (Ceramic)

This study assessed the mechanical properties of hybrid composite vulcanizates made from natural rubber with ceramics industrial waste and carbon black as filler. Ceramic waste was characterized using Xray Diffraction (XRD) and Xray Fluorescence (XRF). Natural rubber (NR) was filled with ceramic powder and carbon black at varying ratios of filler loading as follow; 00, 60/00, 50/10, 40/20, 30/30, 20/40, 10/50, 0/60. The mechanical properties of the hybrid composites evaluated include; tensile strength, young modulus, Flexural Strength, Flexural modulus, Abrasion Resistance and hardness. The result obtained shows the presence of SiO2, Al2O3, Fe2O3, TiO2, CaO, MgO, Na2O, K2O in the ceramic composition and SiO2 appears to be the largest compound in the ceramic. The ceramic/CB ratio of 40/20 shows the highest tensile strength (40.00 MPa), while the modulus was highest with ratio of 60/0. The highest flexural strength (27.00 MPa) was at ceramic/CB ratio 0/60 while the lowest (19.67 MPa) was at ratio of 60/0. The flexural modulus of NR composite began to increases and peaked as the CB increases with the ceramic (40/20 pphr) filler loading at 436.33 MPa. The hardness of the hybrid composite increased as the CB concentration increased with maximum hardness obtained with ceramic/CB ratio 20/40 (47.00 shore A). At ratio of 30/30 the wearing rate was lowest (higher abrasion resistance) at 97.89, Ceramic waste can improve the mechanical properties of the natural rubber vulcanizates by increasing its elasticity, and abrasion resistance if used alone as a filler.

Evaluation of acrylonitrile rubber containing zinc oxide as safety products

AbstractThe goal of this research is to find the ideal formulation with the best antimicrobial performance in terms of rheological, physicomechanical, and lowest toxic properties to produce safety rubber for the children toy's and other industrial products. In order to accomplish this, a number of formulations containing ZnO as activator for vulcanization process as well as an antimicrobial agent at concentrations ranging from 1.5 to 40 phr in the presence of 40 phr of different fillers were prepared. The rheological characteristics of prepared compounded rubber samples were assessed and the cure rate was calculated. The overall rheological test results indicate a raise in minimum and maximum torque along with a fall in scorch and optimum cure time. The compounded NBR was vulcanized as estimated curing time. The results illustrated that the NBR vulcanizates containing various amounts of ZnO and 40 phr talc have the best physicomechanical properties. Also, the scanning electron micrographs indicated surface homogeneity and good dispersion of the NBR components. The cytotoxicity test of the investigated vulcanizates on normal retina cell line gave no cytotoxic effect which assessed their safety. These findings offer useful information for antimicrobial NBR vulcanizates for kid's toys and other safety products.Highlights Synthesis of antimicrobial NBR rubber vulcanizates for safety applications. The antimicrobial agent used was ZnO. ZnO nanoparticles and other ingredients were incorporated with NBR on the ordinary rubber mixer. Rheological, physicomechanical properties and antimicrobial activity of NBR rubber were tested. The products have better mechanical and antimicrobial safety properties.

Impact of an oligomer deep eutectic solvent on structure and properties of natural rubber vulcanizates and their nanocomposites

AbstractRubber nanocomposites exhibit strain softening under large‐amplitude oscillation shear and large‐strain cyclic tension while the softening behaviors are hard to regulate in industry. Herein, an oligomer deep eutectic solvent (DES) synthesized from polyethyleneglycol and tetrabutylammonium bromide is used to mediate the vulcanization and softening behaviors of natural rubber (NR) gums and their nanocomposites. The results show that DES could accelerate NR vulcanization and improve crosslinking density. For the hydrophilic silica nanocomposites, DES could greatly reduce tanδ and weaken weak strain overshoot accompanying Payne and lower percentages damping accompanying Mullins effects. The effects in nanocomposites filled with hydrophilic/hydrophobic silica and carbon black are investigated and compared. The investigation provides a new way for tailoring elasticity and dissipation of vulcanizate nanocomposites filled with hydrophilic silica.

Broadband absorptive metamaterials enhanced by magnetic rubber to broaden bandwidth

A method to extend the operational bandwidth of metal-dielectric-metal (MDM) type absorptive metamaterials is proposed. An ultrathin, five-band absorptive metamaterial with wide-angle absorption and polarization sensitivity in the X-band is designed. The total absorption bandwidth across the five bands, with reflection losses below −10 dB (absorption rate greater than 90 %), is nearly 1 GHz. The physical mechanisms of absorption are analyzed through the distributions of surface current, electric field, and magnetic field. Samples were fabricated and tested, and the results were consistent with the simulation outcomes. To enhance the bandwidth of the absorptive metamaterial and its application prospects, magnetic materials such as barium ferrite and carbonyl iron were introduced into a rubber vulcanization layer, which was then combined with the ultrathin absorptive material to create a novel absorptive material. When the magnetic material content in the rubber layer was 50 wt%, the frequency range with reflection losses below −10 dB increased by approximately nine times, covering 69.5 % of the C-Ku band. This significantly broadens the bandwidth of the pure MDM-type absorptive metamaterial, providing a feasible solution for the design of broadband ultrathin absorptive materials.

Synergistic effect of a new binary accelerator system on curing characteristics and properties of styrene–butadiene rubber vulcanizates

Synergistic effect of a new binary accelerator system on curing characteristics and properties of styrene–butadiene rubber vulcanizates

Exploring the Role of Bamboo Charcoal Powder as Filler in Rubber Vulcanisates

Exploring the Role of Bamboo Charcoal Powder as Filler in Rubber Vulcanisates

The effect of hypo‐sulfonamide accelerators on the induction period of rubber vulcanization based on experiments and molecular simulations

AbstractAccelerators 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 was 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.

The Effect of Different Accelerators on the Vulcanization of EPDM Rubber

: EPDM (ethylene propylene diene monomer) is a type of synthetic rubber. The products of rubber have great importance in every part of life. EPDM rubber has high tensile strength, high tension, toughness, and is weather resistant. Therefore, EPDM (ethylene-propylene-diene rubber) is widely used in many fields. The aim of this study is to examine the effect of accelerator type on mechanical properties and vulcanization characteristics of EPDM rubber. We used the accelerators; thiazole, sulfonamides, dithiocarbamate, thiuram, and guanidine groups. The results show that the fastest cure time and the best tensile strength are achieved with dithiocarbamates for EPDM rubber.

Effect of extreme environments on aging of fluoroelastomers

Fluoroelastomer compositions are used in extreme environments, such as high pressure and high temperature (HPHT), in a wide range of applications in the oil and gas industry. As hydrocarbon production is expanded to deeper formations, and operating temperature and pressure become higher, the material performance of these elastomers becomes more important. Hence, fluoroelastomers face new challenges and require further understanding when these undergo aging. In this study, a practical fluoroelastomer (FKM) composition was aged in deionized water and an alkaline hydraulic fluid up to 31 MPa, 225 °C and 168 hrs. High pressure, high temperature and aging time have deleterious effects on the physical and mechanical properties of FKMs in both the fluids. Spectroscopically, under these conditions, two hydrocarbon-related bands at 2917 and 2850 cm−1 and three fluorocarbon bands at 886, 1158 and 1396 cm−1 in the Fourier Transform Infrared spectra decreased in intensity after aging. The temperature, at which the rate of degradation was maximum, measured through thermogravimetry also decreased under HPHT conditions. It was further observed that the filler particles bound to the rubber leached out during the aging experiment to cause a color change of the fluid. The tensile sheet was delaminated with cracks on the surface under extreme conditions due to rapid changes in the properties of the surface compared to the bulk. Based on the characterization of the aged rubber vulcanizate and the particles leached out into the aging fluid, a mechanism of HPHT aging of FKM vulcanizate is proposed, which would be helpful in designing fluorocarbon compositions in extreme environments.