Vulcanization Network Research Articles

ВЛИЯНИЕ ГИДРОЛИЗАТА КОЛЛАГЕНА НА КИНЕТИКУ ВУЛКАНИЗАЦИИ И ПЛОТНОСТЬ СШИВАНИЯ РЕЗИН НА ОСНОВЕ БУТАДИЕН-НИТРИЛЬНОГО КАУЧУКА БНКС-18

The effect of collagen hydrolysate (CH) obtained from the swim bladder of northern fish species on the set of operational properties of elastomers based on BNKS-18 nitrile butadiene rubber with acrylonitrile content of 18 wt.% was studied. The vulcanization kinetics of elastomeric blends were determined on a D-RPA 3000 rotorlessrheometer (MonTech, Germany). Tensile strength and elastic properties of vulcanizates were determined on an Autograph AGS-JSTD testing machine (Shimadzu, Japan). Frost resistance was evaluated by the value of frost resistance coefficient according to elastic rebound after compression at -20, -30, -40, -50 °C. The density of the vulcanization network of the studied elastomers was determined according to the Flory-Rener equation by the method of equilibrium swelling of vulcanizates in chloroform. The analysis of vulcanization kinetics showed that the introduction of collagen hydrolysate obtained by us into the composition of BNKS-18 based elastomer increased the minimum torque. That is, the viscosity of the studied elastomers increased before the start of the main vulcanization process. As demonstrated in this study, CH significantly affects the crosslinking density of elastomer. Introduction of CH in the composition of elastomers leads to the formation of a sufficiently dense and strong vulcanization network. This is apparently associated with the fact that CH fragments interact with the ingredients of the vulcanizing system and the rubber macromolecules, participating in the structuring of the material. It was found that the introduction of CH increased modulus at 100% elongation and tensile strength, while elongation at break decreased. The maximum value of tensile strength corresponds to the introduction of 3phr of CH and amounts to 16.9 MPa, which is 37% higher in comparison with control elastomers without CH. It was shown that the increase of crosslink density of vulcanization network of the obtained elastomers was accompanied by increase of frost resistance coefficient at -30 and -40 °C. The field of application of the developed materials is manufacturing of rubber seals, cuffs, oil seals, gaskets designed for the Far North and the Arctic equipment.

Design of Vulcanization Intermediates with Low Steric Hindrance Contributing to Vulcanization Network Formation

Sulfur cross-linking, known as vulcanization, is an extraordinarily important process to endow rubbers with practical performances in the rubber industry. However, the steric hindrance of vulcanization intermediates hinders the formation of vulcanization networks, limiting the property enhancement of vulcanized rubbers. To promote the formation of vulcanization networks, our group lowers the steric hindrance of vulcanization intermediates through decreasing the length of alkyl chain. Temperature-dependent Fourier transform infrared spectroscopy suggests the formation of bridging bidentate zinc/fatty acid salt complex (vulcanization intermediates) with different steric hindrances. The reduction in steric hindrance of vulcanization intermediates increases the coordination interactions between sulfur and vulcanization intermediates, promoting the ring-opening of sulfur and formation of vulcanization networks. As a result, with the reduction in steric hindrance of vulcanization intermediates, the properties of vulcanized rubbers improve greatly. This work promotes the formation of vulcanization network through lowering the steric hindrance of vulcanization intermediates, which provides a simple generic strategy for the development of high-performance rubbers.

Creation of special compositions based on butadiene-nitrile elastomers for diesels

In the article, it was determined that furan oligomer added to the composition causes additional structuring in the process of vulcanization, and as a result, the density and hardness of the vulcanization network in the composite increases, and the value of the relative length decreases. It was shown that the optimal amount of furan oligomers in the composition of rubber compounds is equal to 10 weight units per 100 weight units of rubber. With the inclusion of the secondary product of acetylene production in the elastomer compositions, it was found that the amount of carbon-rubber gel and the vulcanization network increased, and the level of vulcanizate shrinkage decreased, which was shown to be mainly due to the presence of oligomeric components on the surface of carbon particles. It is shown that the inclusion of this raw material in elastomeric compositions based on butadiene nitrile rubber increases the interaction at the “rubber-filler” boundary and the formation of additional bonds between rubber macromolecules and functional groups of the oligomer, and as a result, the overall technological and technical properties of the compositions are improved.

Creation of elastomer-based compositions with special characteristics for the wheel-engine block of thermal locomotives

In the article, the measures aimed at preventing vibrations generated in the wheel motor unit, one of the main most responsible units of mainline locomotives, are mentioned. There are different types of gears in the wheel motor unit, and the additional vibration is higher in the gear wheels of the assembled form. Because the gears of this assembly form are made of resinotechnical materials. This suspension element is made of V14 rubber technical material. The original purpose of the article is to use synthetic nitrite rubber SKN-18M instead of V14 rubber technical material based on local standards. It was studied that by changing the ingredients in SKN-18M and the sequence of their addition, it is possible to obtain a detail with improved vibration resistance and load bearing capacity. It was found that the amount of carbon-rubber gel and the vulcanization network of the material increased, the vulcanizate swelling level decreased, which is mainly due to the presence of oligomeric components on the surface of carbon particles. It is shown that the inclusion of this raw material in elastomeric compositions based on butadiene nitrile rubber increases the interaction at the “rubber-filler” boundary and the formation of additional bonds between rubber macromolecules and functional groups of the oligomer, and as a result, the overall technological and technical properties of the compositions are improved.

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.

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.

Comparative Study of the Marinobacter hydrocarbonoclasticus Biofilm Formation on Antioxidants Containing Siloxane Composite Coatings.

No systematic study of antioxidant containing coatings and their anti-biofilm action has been reported so far. The utilization of antioxidants in protective coatings to inhibit marine biofilm formation is a current challenge. The aim of this preliminary study was to prepare, characterize and compare the efficiency of low adhesive siloxane composite coatings equally loaded with different antioxidants against mono-species biofilms formation. Most often participating in the marine biofilms formation, Marinobacter hydrocarbonoclasticus was the test bacterium. Both the biofilm covered surface area (BCSA) and corrected total cell fluorescence (CTCF) (by fluorescent microscopy) were selected as the parameters for quantification of the biofilm after 1 h and 4 h incubation. Differing extents of altered surface characteristics (physical-chemical; physical-mechanical) and the specific affection of M. hydrocarbonoclasticus biofilm formation in both reduction and stimulation, were found in the studied antioxidant containing coatings, depending on the chemical nature of the used antioxidant. It was concluded that not all antioxidants reduce mono-species biofilm formation; antioxidant chemical reactivity stipulates the formation of an altered vulcanization network of the siloxane composites and thus microbial adhesion which influences the surface characteristics of the vulcanized coatings; and low surface energy combined with a low indentation elastic modulus are probably pre-requisites of low microbial adhesion.

The role of natural rubber endogenous proteins in promoting the formation of vulcanization networks

Abstract Non-rubber components are critical in the formation of the natural rubber (NR) vulcanization network, which leads to outstanding mechanical properties of NR. This study reports the effect of NR endogenous proteins (C-serum protein/lutoid protein [CSP/LP]) on the formation of vulcanization networks at the molecular level. Results indicate that CSP/LP has a positive effect on vulcanization. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses demonstrate that the decrease in vulcanization time of CSP/LP is ascribed to coordination interaction between Zn2+ and amide bond. The interaction increases the availability of ZnO in the matrix, thereby promoting the formation of the vulcanized network. CSP/LP also participates in the construction of the vulcanization network as a new crosslinking point, thus increasing crosslinking density and improving the mechanical properties of the NR. This study provides new research ideas for studying the relationship among component–structure–property of NR materials and developing high-strength and high-toughness elastomer materials.

Effect of Production Technology of Hydrin T6000 Elastomers on Their Properties and Structure

The influence of the technology for producing elastomer materials based on epichlorohydrin rubber of Hydrin T6000 brand on physical-mechanical properties, structure formation, and frost resistance is studied. Differences in the properties of vulcanizates are revealed due to the formation of various sulfide bonds in a vulcanization network with different densities. The use of rubber swelling technology in a plasticizer leads to a screening effect, which reduces the interaction of the filler with the polymer. On the plus side, this effect improves low-temperature properties, and on the minus side, deteriorates physical-mechanical properties of the material.

Effect of protein on the thermogenesis performance of natural rubber matrix

Under high-speed strain, the thermogenesis performance of natural rubber products is unstable, leading to aging and early failure of the material. The quality of rubber latex and eventually that of the final products depends among others on the protein content. We found that when the protein is almost removed, the heat generated by the vulcanized rubber increases rapidly. After adding soy protein isolate to the secondary purification rubber, the heat generation of the vulcanized rubber is reduced, and the heat generation is the lowest when the added amount is 2.5–3.0 phr, which on account of protein promotes the construction of a vulcanization network and increases the rigidity of the rubber chain, resulting in a decrease in the potential frictional behavior of the rubber chain during the curl up-extension process.

Synergism of Triallyl Cyanurate and Divinylbenzene in a Dynamically Vulcanized Blend of Polypropylene with Hydrogenated Styrene–Butadiene–Styrene Block Copolymer

The synergistic effect of divinylbenzene and triallyl cyanurate on the properties and structure of the thermoplastic vulcanizate prepared from a blend of polypropylene and hydrogenated styrene–butadiene–styrene triblock copolymer by vulcanization under dynamic conditions with 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane was revealed. The synergism consists in the enhancement of the strength, increase in the relative elongation, and decrease in the compression set to a greater extent then when using divinylbenzene or triallyl cyanurate separately. The synergism is caused by the increased gel fraction content and vulcanization network thickness, with preservation of the higher molecular mass of the polypropylene matrix.

Study on the effect of modified and unmodified silica on the properties of natural rubber vulcanizates

AbstractIn the article, the effects of silica (silicon oxide) on some properties of natural rubber (NR) were studied. Silica used are unmodified (SiKBT) and modified with triethoxi silane propyl tetrasunfite (SiBT). It is shown SiBT increases vulcanization network density (VND), so it enhances strength and elastic properties of NR. In contrary, SiKBT decreases VND and reduces, but has almost no effect on strength of NR. Silica, both modified and unmodified, are assumed to improve network regularity of NR that change thermal degradation behavior of materials and keep the strength of NR‐SiKBT compound unchanged.

Influence of the Peroxide Vulcanization Coagent on the Properties of a Blend of Polypropylene with Hydrogenated Styrene-Butadiene-Styrene Block Copolymer

The dependence of the properties of a polypropylene blend with hydrogenated styrene-butadiene-styrene block copolymer, prepared under the conditions of dynamic vulcanization, on the concentrations of the peroxide and various vulcanization coagents (triethylene glycol dimethacrylate, triallyl cyanurate, triallyl isocy-anurate) was studied. The influence of the kind and concentration of the peroxide and coagent on the deformation and strength properties of the thermoplastic vulcanizate obtained was accounted for by the experimental data on variation of the gel fraction content of the mixture, vulcanization network density, and degree of crystallinity and molecular mass of polypropylene. The possibilities and conditions for reducing the compression set and enhancing the oil resistance of the thermoelastoplastic were determined.

Compatibilization of polypropylene and butadiene–acrylonitrile rubber using an organic peroxide and an oligoether acrylate

The relationships and causes of changes in the deformation and strength properties of a blend of polypropylene with butadiene–acrylonitrile rubber with variation of the content of an organic peroxide, 2,5-dimethyl- 2,5-di(tert-butylperoxy)hexane, and an oligoether acrylate, triethylene glycol dimethacrylate, were studied. The observed changes in the deformation and strength properties of the blend were accounted for on the basis of the experimental data on the density of the vulcanization network of the butadiene–acrylonitrile rubber, on the morphological structure of the blend, on the adhesion between the polymers, and on the degree of crystallinity and molecular mass of polypropylene.

Polyurethane elastomers based on oligobutadienediol NISSO PB G3000

The hardening possibility of the new oligobutadienediol was studied. The influence of the ratio between the isocyanate and hydroxyl groups and the amount of glycerol on the mechanical properties, the degree of cross-linking, vulcanization network structure, and the relationship between the amount of the chemical and physical grid nodes of oligourethanes were investigated.

Structure and properties of thiokol sealants modified with organosilanes

The effect of functionalized organosilanes on the properties of sealants based on liquid Thiokol NVB-2 was examined. The role of these agents in formation of the vulcanization network and of chemical bonds with the substrates was analyzed.

Effect of ambient temperature on electrical treeing characteristics in silicone rubber

In this paper, electrical treeing was investigated in room temperature vulcanized (RTV) silicone rubber (SiR) over a range of ambient temperatures. An ac voltage with a frequency of 50 Hz was applied between a needle-plate electrode to initiate the electrical tree at different ambient temperatures. Both the structures and the growth characteristics were observed by using a digital microscope system. Obtained results show that the tree initiates from a single branch with a white gap. Four typical tree structures, namely branch, bush, pine branch and bush-pine mixed tree, were observed within the sample. The occurrence of tree structures changes with the increase of ambient temperature, in which branch tree takes up a great proportion at 30°C while bush tree becomes dominated as the temperature rises up to 90°C. Meanwhile, the cumulative inception probability within the same time decreases obviously with the increase of ambient temperature. The growth rate of the tree is closely related to the ambient temperature. It is suggested that the increase of vulcanization network density and elastic modulus with ambient temperature may have great influence on the treeing characteristics (including growth rate, fractal dimension and treeing proportion).

Crumb Rubber–Modified Asphalt: Microwave Treatment Effects

Crumb rubber pretreatment by microwave irradiation before blending with an asphalt matrix improves the properties of rubber–asphalt blends. This treatment cleft the surface vulcanization network, resulting in higher surface activity of the crumb rubber and improved compatibility with asphalt. This new rubber blend exhibited minor temperature susceptibility behaviors and high ductility at 5°C and an improved viscoelastic nature and storage stability. Characterization has also been performed to elucidate the mechanism for this improvement using a microwave treatment technique.

Influence of the nature of a curing agent on the peculiarities of formation of vulcanization networks in polysulfide sealants

The molecular mobility of vulkanizates of liquid thiokols cured with various vulcanizing agents was studied by the NMR method in a wide temperature interval. The influence of the nature of vulcanizing agents and the structure of the forming vulcanization network on the change in the character of molecular mobility in vulcanizates of polysulfide oligomers was established. The correlation of effective (υeff) and chemical (υch) densities of vulcanization networks of thiokol sealants with parameters of the NMR spectrum of the latter was found. The influence of the nature of a curing agent on the peculiarities of the formation of vulcanization networks of polysulfide oligomers is discussed.

New characteristic of tensile stress–strain properties in rubbers

Usually, the tensile stress–strain relationship in rubbers looks like an S-shaped curve. The knee point on a curve for non-crystallized gum is related to limited stretchability of the vulcanization network, hence it is observed for pure-gum and filler-loaded rubbers. The bending occurs when the rubber phase reaches a definite strain (start of developing limited network stretchability), so one may assume that at a knee point the strain in the rubber phase is the same for both pure-gum and filler-loaded rubbers. This assumption enabled normalization of stress–strain curves for pure-gum and filler-loaded rubbers and to use a single curve. Knee-point strain is not a geometrical phenomenon, but a structural characteristic of a rubber, since it is related to vulcanization network density, i.e. to the elastic modulus.