Structure Of Rubber Research Articles

Выбор ускорителей вулканизации для резин на основе эпихлоргидринового каучука

The effect of vulcanization accelerators on the structure and properties of rubbers based on Hydrin T6000 epichlorohydrin rubber has been studied. Mercaptobenzthiazole (MBT) in the amount of 1.5 pts.wt., tetramethylthiuram disulfide (TMTD) — 0.5 – 1.5 pst.wt. were used as accelerators and N,N’-diphenylguanidine (DPG) — 0.5 – 1.5 pst.wt., which represent a triple system of accelerators. The choice of accelerators is based on the possibility of obtaining a vulcanization spatial structure of different sulfide content: thiuram group accelerators promote the formation of mono-, disulfide bonds; guanidine — polysulfide bonds, and thiazole groups — from carbon-carbon to polysulfide with varying degrees of sulfide. According to the results of the study of physical and mechanical properties, the determination of the parameters of the spatial grid and the study of the dynamic behavior of rubber, differences were revealed due to the formation of a spatial structure with different types of cross-links and density. It is shown that rubber containing 1.5 pst. wt. MBT, 0.5 pst. wt. DFG and 0.5 – 1.0 pst.wt. TMTD due to the manifestation of a synergistic effect on the formation of a vulcanization network of a certain density and the ratio of poly-, di- and monosulfide cross-links. Thus, the use of a group of accelerators with different functional effects makes it possible to obtain vulcanizates with an optimal set of technological and operational properties.

Features of structure formation in crumb rubber modified bitumen

The research is devoted to developing the science-based technological solution for obtaining crumb rubber modified bitumen (CRMB) with improved stability. The technological solution provides a preliminary process of devulcanization of crumb rubber in hydrocarbon plasticizer in the presence of stabilizing agent and subsequent preparation of CRMB. Using fluorescent microscopy, it was established that the formation of a branched structure of crumb rubber is achieved in the waste industrial oil, indicating devulcanization processes. It was found that the most compatible with crumb rubber is a hydrocarbon plasticizer with a high content of naphthenic oil. Synthetic wax was found to be of greater interest as a stabilizing agent, and its application in an amount of 3% allows the formation of a stable CRMB structure and stabilizes the devulcanization process. The test results of obtained CRMB showed that their viscosity corresponds to the requirements for PG bitumen

LONGITUDINAL RELAXATION OF NUCLEAR MAGNETIZATION IN RUBBER SOLUTIONS: POLYISOPRENE PROTONS

The longitudinal (spin-lattice) relaxation times of Т1 of protons are measured selectively (for various structural groups) at a nuclear magnetic resonance frequency of 700 MHz in a solution of an industrial sample of Cariflex-IR0307 isoprene rubber in deuterated benzene. It is shown that the value of T1 significantly
 depends on the structural position in the polyisoprene chain. The highest values of T1 are obtained at double bonds of monomer units in the cis-configuration and the methyl group of the trans-unit, the smallest values were obtained for the methine and methylene protons of the 3,4-unit, with a difference of two to three times. The questions of measurement accuracy are considered. Practical recommendations are formulated for the conditions of recording high-resolution NMR1H spectra at quantitative analysis of the structure of isoprene rubbers.

A Full Range Experimental Study of Amplitude- and Frequency-Dependent Characteristics of Rubber Springs

This paper provides a comprehensive understanding of the amplitude- and frequency-dependent characteristics of rubber springs. The dynamic nonlinear inelasticity of rubber is a key academic problem for continuum mechanics and a bottleneck problem for the practical use of rubber structures. Despite intensive efforts witnessed in industrial applications, it still demands an unambiguous constitutive model for dynamic nonlinear inelasticity, which is known as the Payne effect. To this end, three types of rubber springs (shear-type (ST), compression-type (CT) and shear-compression-combination-type (SCCT)) were tested with amplitude and frequency sweeps in different conditions. We investigated and present changes in dynamic stiffness and loss factor with amplitude, frequency and the hysteresis loops of different rubber springs. We also propose a hypothesis and research strategy to study a constitutive model involving multiple factors of hyperelasticity, the Mullins effect, viscoelasticity and the Payne effect, which we hope will provide new ideas for the establishment of a constitutive equation.

Assessing herb layer composition under jungle rubber in Sungai Manau Forest, Jambi, Indonesia: indicator species and tree regeneration potential

Abstract. Siswo, Yun CW, Kim H, Lee J, Atmoko BD, Brahmantya L. 2022. Assessing herb layer composition under jungle rubber in Sungai Manau Forest, Jambi, Indonesia: indicator species and tree regeneration potential. Biodiversitas 23: 5247-5257. Most of the post-logged forests in Sumatra have been transformed into various land cover types, including plantations and secondary forests. Among plantation systems, rubber agroforestry (jungle rubber) is preferable since it resembles natural forests, which still maintain high biodiversity. While previous studies have been focused on the floristic diversity, composition and structure of jungle rubber, limited research has investigated indicator species and tree regeneration in jungle rubber. This research aimed to compare herb layer composition including species diversity, indicator species and tree regeneration potential between jungle rubber (JF) and the existing natural growing forests, including undisturbed post-logging forest (UF), mixed regrowth forest (MF) and newly regrowth forest (NF), in Sungai Manau Forest, Jambi, Indonesia. We conducted a vegetation survey and subsequently analyzed the data using some comparative analyses, indicator species analysis and regeneration status analysis. Our results showed significant differences in herb layer communities among all land cover types (T= -18.91, p=0.000). Although JF and all-natural growing forests showed equal indices of diversity, each land cover type showed its own indicator species, reflecting their environmental conditions. However, indicator species for JF were mostly similar in character to that in MF with non-native semi-shade-tolerant species. Meanwhile, all indicator species for UF were native shade-tolerant species and the indicator species for NF were fully non-native shade-intolerant species. JF is also equal to MF in seedlings availability and tree regeneration potential by showing an equal number of seedling species and the number of individuals where most of the seedlings in both land cover types were pioneer species with “good regeneration ”status”. Our finding suggested that JF had a similar potential to MF in the succession process. Therefore, jungle rubber can be a good alternative when a plantation system is inevitable in a post-logging forest.

Experimental and application of continuous regeneration of waste rubber

AbstractCombined with the Serial Rubber Continuous Mixing Device (SRCMD) and custom‐built rotors, the real continuous regeneration of waste rubber was realized. The upstream mixer effectively solves the problem of pretreatment of waste rubber and realizes its preliminary regeneration. The downstream twin‐screw extruder realizes supplementary regeneration and plasticized extrusion of waste rubber. The optimal process parameters for preparing SRCMD‐reclaimed rubber were explored through orthogonal experiments. Compared to the commercially‐reclaimed rubber produced by the traditional vulcanization tank high‐temperature regeneration method, the SRCMD‐reclaimed rubber well retains the main chain structure of waste rubber and has obvious advantages in various properties. The conveyor belt coverings made by partially replacing styrene butadiene rubber with SRCMD‐reclaimed rubber fully meet the requirements of the national standard in all properties and are better than commercially‐reclaimed rubber, which has good application prospects and provides a guide for promoting the industrial transformation of recycled rubber.

Characterization and study of the vulcanization characteristics of ultra‐cold‐resistant reactive chlorinated acrylic rubber prepared by emulsion polymerization

AbstractIn a system initiated by potassium persulfate, an ultra‐cold‐resistant reactive chlorinated resin rubber was synthesized by emulsion polymerization. In this emulsion polymerization, ethyl acrylate and butyl acrylate were used as the main components of the rubber monomer. 2‐Methoxyethyl acrylate was used as a cold‐resistant monomer, and vinyl chloroacetate was used as a vulcanized monomer. Fourier transform infrared spectroscopy, thermogravimetry–gas chromatography–mass spectrometry, 1H NMR, 13C NMR and other rubber detection standards were used to characterize the structure and properties of the synthetic acrylate rubber. Studies showed that acrylate rubber was synthesized by emulsion polymerization, and each monomer achieved random copolymerization with high conversion. The synthetic acrylate rubber has excellent low‐temperature resistance (the brittleness temperature is −36.5 °C). In addition, the rubber has excellent mechanical properties and a high vulcanization speed and is a fast‐vulcanizing acrylic rubber. © 2022 Society of Industrial Chemistry.

The Effects of Carbon-Silica Dual-Phase Filler on the Crosslink Structure of Natural Rubber.

Carbon–silica dual-phase filler (CSDPF)/natural rubber (NR) vulcanizate was prepared by mechanical blending, followed by a hot-press vulcanization. The dispersion of CSDPF in the NR matrix and the effects of CSDPF on the filler–rubber interaction and structure of the rubber network were studied. Scanning electron microscope results showed that CSDPF dispersed uniformly; however, there were some aggregates of CSDPF when loading too many fillers. With an increase in CSDPF, the interaction between CSDPF and NR chains increases, which was detected by bound rubber in the CSDPF/NR compound. The spectra of solid-state nuclear magnetic resonance revealed that CSDPF could promote the formation of poly-sulfidic crosslink in the rubber vulcanization network. Further, the molecular chain movement ability of vulcanizates decreases according to the spin–spin relaxation of 1H nuclei in CSDPF/NR compounds. The crosslink density of vulcanizate increases, while the chemical crosslink and physical crosslink in the vulcanization network also increase according to the tube model.

Structure-Property relationships in natural rubber representing several clonal varieties of Hevea Brasiliensis

In this study, the relationships between the structure of unvulcanized rubber and vulcanizate properties were investigated for the three natural rubber clones: RRIT251, PB235, and RRIM600. The highest tensile properties of rubber vulcanizates were achieved from the PB235 clone whereas the RRIM600 showed the lowest. The PB235 contained the largest average molecular weight (Mw) with the narrowest molecular mass distribution (MWD), whereas the least Mw was for RRIM600 with the broadest MWD. The highest protein contents were noticed in RRIM600 where the highest gel formation was found. In contrast, the PB235 showed the smallest amount of proteins and gel contents. Based on this finding, the results clearly suggested that the Mw represented as a key factor controlling the mechanical properties of vulcanizates. This was because the higher average Mw provide the greater active sites available for crosslinking reaction, while the protein content governed the gel formation in the unvulcanized rubber.

Dynamic Model and Parameter Identification of Magnetic Liquid-Double-Suspension Elastic-Supported Thrust Bearing

In terms of the heavy load and low viscosity operation conditions of the marine rim-driven thruster (RDT), a novel Magnetic Liquid-double-suspension Elastic-supported Thrust Bearing (MLETB) is designed. The MLETB combines the structural features of the Rubber-supported Water-lubricated Thrust Bearing (RWTB) and Permanent Magnet Bearing (PMB). To investigate the axial stiffness and damping of the bearing, the dynamic model of MLETB incorporating a multi-layer structure is developed. Simulation indicates that the dynamic performance of the MLETB is close to that of the RWTB, but the load capacity of the MLETB is better. Besides, the load is not the most important factor to affect the dynamic performance. The parameter identification method is proposed to analyze the experiment results based on the water-lubricated bearing test rig, which show that the MLETB has a dilemma between the load capacity and dynamic performance that its stiffness and damping will be seriously affected by the specific rubber structure.

Design of bionic tire tread compounds with pit structures and the improvement mechanism of wear and wet grip resistance

Design of bionic tire tread compounds with pit structures and the improvement mechanism of wear and wet grip resistance

Formation of silicone thin films by ArF excimer laser induced photo‐desorption

AbstractLow molecular weight silicones were ejected from silicone rubber target irradiated by a 193 nm ArF excimer laser through the photo‐desorption. The ejected silicones were successfully deposited on a fused silica glass substrate in air. An approximately 0.3 mm of the target‐substrate distance was required for the deposition. The deposited silicones became a thin film, showing an interference color when the ArF excimer laser was irradiated for a long time. Chemical bonding state of the formed thin films was analyzed by the Fourier transform infrared spectroscopy. The thin films were slightly different from the original silicone rubber structure, still it was composed of Si‐O‐Si bonds and Si‐CH3 bonds. Also, OH bonds were clearly produced in the silicone thin films. As a result, contact angle of water on the silicone thin films was measured to be approximately 20 degrees, indicating a hydrophilic property.

The Relationship of the Polymer Molecular Structure and the Dynamic Mechanical Property Under High Pressure

The dynamic mechanical properties of the viscoelastic polymer materials are usually considered to be the key parameters for the vibration damping or acoustic materials. The relationship between the molecular structures of the random copolymer butadiene styrene rubber (SBR) obtained through the anionic polymerization method and their dynamic mechanical parameters under high pressure is studied to explore the energy loss mechanism of the polymer materials applied in the special conditions such as high pressure. The dynamic mechanical parameters were tested though experimental methods with pressure chambers, which can supply high pressure to the polymer samples. The results show that the most important effect factor of the molecular structure is the ratio of the content of the stiffer segments composed of styrene in the SSBR molecular chain to the softer ones composed of 1, 4-butadiene. This can be attributed to the stiffer segments supplying bigger free volumes for the molecular motion and higher modulus to resist to the high pressure, and the softer segments endue the effective energy loss ability to the polymer chains. However, the mass ratio of the stiffer and softer segments should be in an appropriate range, which the content of the styrene must be less than 40%.

Effect of modified rubber powder on the mechanical properties of cement-based materials

There are two common problems in the application of rubber aggregate concrete (RAC). One problem is that the rubber aggregate floats easily, which leads to a reduction in the workability of the mixture and delamination of the matrix. Another problem is that the mechanical properties of RAC are greatly reduced after hardening due to the poor interfacial bonding between rubber and the cement matrix (R–C). In this study, a novel modification method of waste rubber powder (WRP) combining mechanochemistry action, ultrasonic energy accumulation and the coating effect was proposed. The particle size distribution, specific surface area, hydrophilicity, morphology and structure of rubber were characterized by a laser particle size analyser, scanning electron microscopy (SEM), etc. The distribution of WRP in the cement-based materials was determined. The interfacial bonding and microstructure of R–C were analysed by SEM. The compressive and flexural strengths of cement-based materials with different contents of rubber were studied. The results showed that the R–C interface was significantly improved, and rubber particles were uniformly distributed in the cement mortar. The particle size of rubber particles showed a standard normal distribution, the surface cracks and pores were filled and coated, and the hydrophilic angle decreased from 94.6° to 68.0°. The cracks and voids of the R–C interface disappeared, and the compressive and flexural strengths of the mortar increased by 70% and 50%, respectively. The R–C interface and the distribution of rubber particles were found to play a major role in influencing the mechanical properties of RAC.

Thermal annealing of natural rubber films controls wettability and enhances cytocompatibility

In spite of the widespread use of natural rubber in regenerative therapies, thermally induced modifications of its complex chemical structure and their effect on the surface properties and the cell response (attachment-adhesion-proliferation) are still an unexplored topic. Here, we demonstrate how thermal treatments enhance the cell response due to changes to the inner and surface structures of natural rubber. In situ studies of the temperature effects conducted via infrared spectroscopy revealed both molecular rearrangements and anharmonic effects in the polymeric lattices. Thermal treatments at different temperatures allowed to control the wetting regime. Contributions of different surface parameters to the wettability were decoupled by statistical analysis of the principal component. The polar component of the surface free energy was recognized as the main surface player, which influences cell spreading, attachment, proliferation, and tissue growth. A simple thermal annealing of the natural rubber film at 373 K alters the local structure of the latex inducing an increase in cell viability. The experimental-statistical analysis approach allows an accurate correlation of physicochemical properties with cell supportability. The results highlight the potential of natural rubber polymers by tuning surface wettability, via simple thermal treatment, for biomedical applications.

Dynamic heterogeneity and nanophase separation in rubber-toughened amine-cured highly cross-linked polymer networks

Solid state nuclear magnetic resonance (NMR) spectroscopy and small-to wide-angle X-ray scattering (SWAXS) methods were used to characterize the heterogeneous dynamics and polymer domain structure in rubber modified thermoset materials containing the diglycidyl ether of bisphenol A (DGEBA) epoxy resin and a mixture of Jeffamine reactive rubber and 4,4-diaminodicyclohexylmethane (PACM) amine curing agent. The polymer chain dynamics and morphologies as a function of the PACM/Jeffamine ratio were determined. Using dipolar-filtered NMR experiments, the resulting networks are shown to be composed of mobile and rigid regions that are separated on nanometer length scales, along with a dynamically immobilized interface region. Proton NMR spin diffusion experiments measured the dimensions of the mobile phase to range between 9 and 66 nm and varied with the relative PACM concentration. Solid state 13C magic angle spinning NMR experiments show that the highly mobile phase is composed entirely of the dynamically flexible polyether chains of the Jeffamine rubber, the immobilized interface region is a mixture of DGEBA, PACM, and the Jeffamine rubber, with the PACM cross-linked to DGEBA predominantly residing in the rigid phase. The SWAXS results showed compositional nanophase separation spanning the 11–77 nm range. These measurements of the nanoscale compositional and dynamic heterogeneity provide molecular level insight into the very broad and controllable glass transition temperature distributions observed for these highly cross-linked polymer networks.

Removal of Proteins and Its Effect on Molecular Structure and Properties of Natural Rubber

Removal of protein from natural rubber was carried out via deproteinization of natural rubber in the latex stage. Then, its effect on the molecular structure and properties of natural rubber was investigated. Urea, SDS, and acetone were used as denaturing agent, a surfactant, and a polar solvent in the deproteinization, respectively. Various deproteinized natural rubbers were obtained after one, two, and three times of centrifugation with and without acetone, namely DPNR1, DPNR2, DPNR3, DPNR1-A, DPNR2-A, and DPNR3-A. It was found that the total protein content significantly decreased as increasing the number of centrifugations; however, the total fatty acid contents showed a slight decrease. Structural characteristics analyzed by nuclear magnetic resonance spectroscopy indicated no changes in the chemical structure of natural rubber after deproteinization. However, the removal of proteins significantly enhanced the resolution of the NMR signals. Gel content and tensile properties of natural rubber showed a decrease in the removal of proteins, which was associated with the decrease in the number of the inherent branching points formed in natural rubber.

Mechanism of the foaming agent‐assisted microwave drying process on the construction of natural raw rubber network and cross‐linking network

AbstractThe drying process of natural rubber latex significantly affects the structure of the raw rubber network and vulcanizate crosslinking network, resulting in various anti‐aging performances. In the present study, a microwave generator was used as an efficient source of clean energy; potassium oleate was introduced as a foaming agent to increase the porosity and water loss channel of the latex system. Aiming at dehydrating and drying natural rubber latex efficiently, an aging resistant rubber composite was prepared. Meanwhile, the mechanism of the foaming agent‐assisted microwave drying process on the raw rubber network and the cross‐linking network was studied. The experimental results show that the prepared rubber using by this process has higher plastic retention and fluidity. Moreover, it contains more non‐rubber components (e.g. protein and acetone extract) and better network structure of raw rubber and vulcanized rubber. It is found that applying this process increases the tensile product by 13.5% and the retention rate of the tensile product after aging by 15.3 times. This process is important for the development of the rubber industry in the direction of green environmental protection, energy conservation, and high efficiency.

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.

Rubber–Bitumen Interaction of Plant-Blended Rubberized Bitumen Prepared under Various Blending Conditions

Abstract Rubberized bitumen produced from waste tire rubber has been widely used as a sustainable paving material worldwide. However, different production conditions may lead to rubberized bitumens with different performances. This study aims to understand the mechanism of the physicochemical interaction between rubber particles and virgin bitumen of the rubberized bitumens prepared in the plant under various blending conditions. To achieve this objective, samples of the rubberized bitumens prepared in the plant under four conditions were first collected and then characterized through various laboratory tests. The infrared spectra and gel permeation chromatograph test results demonstrated that the main crosslinking structures of rubber remain stable and undamaged during the whole production period, although some chemical reactions—such as oxidation, decarboxylation, and devulcanization—occur. The storage stability test results implied that the plant-blended rubberized bitumen exhibits no obvious phase separation after storage at 163°C for 48 h and becomes more stable as the blending time prolongs. The rheological test results indicated that the rubber–bitumen interaction is mainly composed of early stage absorption and swelling of rubber particles, continuous emission of volatile bitumen components, and late-stage partial degradation of fully swollen rubber particles. The surface images of the rubberized bitumen confirmed that as the blending time increases, the surface of rubberized bitumen becomes smoother, as a result of the improved rubber–bitumen interaction.