Thermal Vulcanization Research Articles

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

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

FEATURES OF THE STRUCTURE AND PROPERTIES OF COMPOSITIONS OF MODIFIED ISOPRENE RUBBER WITH CHLORIDE-CONTAINING AND EPOXY COMPOUNDS

The effect of HCPX and EC as a stitching agent during thermal vulcanization of modified isoprene rubber (SKI-3- PVA) 80:20 in the presence of zinc oxide was studied. Studies of structural changes occurring in vulcanizates based on SKI-3-PVA under the influence of heating have been carried out. Based on the data of IR spectroscopy and the gel fraction, the rate of reactions with hexachloroparaxylenes (HCPX) between the studied low molecular weight compounds was studied. Considerations are made about the nature of the vulcanization action of the studied structuring systems and the features of their influence on the parameter of the spatial network and the physical and mechanical properties of vulcanizates. The effect of heating time on the content of total and combined chlorine in samples containing HCPX and ZnO was studied. The number of stitched HCPX molecules per cross-link was calculated

Nanoarchitectonics of hierarchical FeCdS-CdS nanorods and Ni-Salens for high-efficiency photocatalytic hydrogen production

A highly efficient photocatalytic system was rationally designed and prepared for hydrogen production under visible light. Through a two-step cation exchange reaction with Cd2+ ions under alkaline environment, the metal hydroxide shells were assembled on the surface of MIL-88A. Then the shells were integrated into a heterogeneous metal sulfide shell layer via a thermal vulcanization reaction, which also achieved the doping of transition metals simultaneously. The formed hybrid structure can reduce the volume-surface diffusion length and recombine photogenerated electrons. Moreover, using the molecular cocatalyst (Ni-Salens) in the photocatalytic system can efficiently induce the transfer of photogenerated electrons, thereby improving the catalytic efficiency and stability of this catalytic system. The maximum amount of hydrogen production reached 7956 μmolg-1h-1, significantly higher than that of CdS-based catalysts reported recently. The current work provides an effective and feasible strategy to improve the efficiency of photocatalytic H2 production.

Wafer-scale MoS2 for P-type field effect transistor arrays and defects-related electrical characteristics

Because of their fascinating electrical/optoelectrical characteristics, two-dimensional molybdenum disulphide (MoS2) attracts much attention recently. However, it is still a challenge to fabricate wafer-scale MoS2 nanofilms of controlled thickness and high quality and that, limits their application. Here, a two-step thermal vulcanization method is proposed to fabricate wafer-scale MoS2 nanofilms with different thicknesses (3-10 layers). The synthesized MoS2 nanofilms have high uniformity and good quality. Furthermore, back gate field effect transistor (FET) arrays were fabricated based on these wafer-scale MoS2 nanofilms. The FET devices showed good electrical performance, mobility in the range of 0.44 ~ 0.96 cm2V−1s−1 and on/off ratio of ~103. Here, first-principle calculation was used to analyse the different types of defects observed in the tri-layer MoS2, the doping effects induced by the defects were also discussed. This work provides a reliable way to fabricate wafer-scale MoS2 nanofilms and give a detailed study of the electrical properties of multilayers MoS2 nanofilms paving the way for the manufacture of two-dimensional semiconductor materials.

Microstructure and Wear Resistance of WS2/W Composite Coating on TC4 Titanium Alloy Surface

In order to achieve the demand for improving the wear resistance of titanium alloy surfaces, a combination of magnetron sputtering (PVD), chemical vapor deposition (CVD) and thermal vulcanization methods is used to prepare highly wear-resistant WS2/W Composite coating on the surface of TC4 titanium alloy. Scanning electron microscope (SEM), X-ray diffractometer (XRD) and X-ray energy dispersive spectrometer (EDS) were used to characterize the micro-morphology, microstructure and chemical composition of the composite coating. The micro-hardness and wear resistance of the composite coating were tested. The results show that the thickness of each layer of the WS2/W composite coating prepared by the experiment is about 16μm and 60μm respectively, the coating structure is dense, and the interface between the layers is obvious. The average micro-hardness of WS2 layer and W layer are 110.4HV and 740.1HV respectively. The surface friction factor of WS2/W composite coating is 0.15, which is about 18% of the matrix (0.85). The wear rate is 1.184 × 10-6mm3·mm-1, which is about 45% of the substrate (1.628 × 10-6mm3·mm-1), which has better wear resistance and anti-friction characteristics.

Effect of electron beam irradiation on aging time, thermal vulcanization kinetic and mechanical properties of SSBR/NR/BR compounds filled with silica

A ternary rubber compound based on solution styrene–butadiene rubber (SSBR), natural rubber (NR) and polybutadiene rubber (BR) filled with silica were studied. This uncured compound was electron beam irradiated at different doses and later was vulcanized.The influence of electron beam irradiation on the pre-vulcanized compound at different radiation doses, and a later aging time, on Mooney relaxation were investigated. These results were analyzed using the Wu–Abbott model and the generalized Maxwell relaxation model and were associated with swelling measurements, confirming the influence of the crosslinking reaction under the irradiation process before the thermal vulcanization.The impact of the irradiation treatment on the thermal vulcanization kinetics was also studied at several temperatures in the range between 140 to 180 °C. The reduction of the induction time of the compounds with the radiation dose was confirmed by means of rheometer test. The relationship between the induction time and the cure temperature approaches Claxton-Liska model. The cure kinetic of rubber compounds was analyzed in the frame of the Isayev-Deng model showing satisfactory results.After the thermal curing, swelling measurements and mechanical properties were done to characterize the ternary rubber compounds, confirming the influence of the irradiation process on the obtained morphology and performance.

Effect of electron‐beam irradiation on the thermal vulcanization of a natural rubber compound

ABSTRACTThe influence of electron‐beam irradiation on the thermal vulcanization curing kinetics of a natural rubber compound was investigated by means of rheometric tests [moving die rheometry (MDR)] and differential scanning calorimetry (DSC). Differences in the storage moduli of compounds with different radiation doses were observed and assigned to a plasticizer effect by the zinc stearate mainly formed in the mixing stages; this compound migrated to the interphase region. This fact was confirmed by Fourier transform infrared spectroscopy. From the measurements performed by MDR and DSC testing, the induction time (to) was analyzed in the frame of the Claxton–Liska model, whereas the kinetic behavior of the nonirradiated and pre‐irradiated compounds were satisfactorily fitted with the Isayev–Deng and Kamal–Ryan models. Additionally, both curing characterization techniques corroborated the fact that the pre‐irradiated rubber compound showed an earlier t o and a lower activation energy in comparison with the nonirradiated compound. These facts were attributed to the effect of irradiation on the free sulfur content present in the rubber compound, which promoted more activated precursor species to crosslink with rubber. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47216.

Properties of hydrophobically-modified graphene oxide (HG)/butyl rubber (IIR) nanocomposites prepared by shear mixing process

Butyl rubber (IIR)/hydrophobically modified graphene oxide (GO) (HG) nanocomposites were prepared via shear-induced compounding. Hydrophilic GO was synthesized through the chemical oxidation of graphite (GP) and modified hydrophobically by octadecylamine which has a hydrophobic long alkyl chain. The obtained HG was characterized by Fourier transform infrared and wide-angle X-ray diffraction (WAXD) patterns. It was well dispersed in toluene for more than 30 days under stationary condition. The IIR/HG nanocomposites were prepared by the shear mixing process and followed by thermal vulcanization process through compression molding. Their properties were studied using oscillating disk rheometer, universal testing machine, differential scanning calorimetry, thermogravimetric analysis, WAXD patterns, and scanning electron microscope analysis. The hydrophobic HG was dispersed at the nanoscale within IIR matrix, and the resulting nanocomposites had significantly reduced curing time. The overall tensile properties were enhanced.

Carbon Nanotube Elastomer Composites

Composites of multi walled carbon nanotubes and several synthetic rubbers as well as natural rubber were investigated regarding their mechanical properties, electrical and thermal conductivity and vulcanization properties. The composites were prepared by a melt mixing process. Induction and cure times obtained from rheometer curves exhibited a considerable decrease with increasing filler loading and kinetic investigations using a first order model indicated a distinct reduction of the activation energy. An examination of the crosslink density by equilibrium swelling and hysteresis tensile testing showed a strong increase with carbon nanotube content. The analysis of the thermal conductivity revealed the presents of a considerable interfacial thermal resistance which restricts the contribution of carbon nanotubes to the composite thermal conductivity. The electrical percolation thresholds of the melt compounded composites depend on processing procedure as well as elastomer and CNT type. At least a partial exfoliation of the CNT aggregates was reached.

Two-dimensional mathematical model of nonstationary heat conduction during thermal vulcanization of elastomeric coatings on a fabric backing

A two-dimensional mathematical model of nonstationary heat conduction during thermal vulcanization of elastomeric coatings on a fabric backing is examined under convective heat exchange with the ambient medium. As compared with a corresponding one-dimensional model, the solution obtained for the two-dimensional mathematical model of nonstationary heat conduction makes it possible to improve the quality of vulcanization of the final product, and lower the effect of incomplete or excessive vulcanization.

A model for the cooling of an elastomer coating on cloth after thermal vulcanization

A model is considered for the cooling of an elastomer coating on a cloth basis when coiled into a roll. Calculations have been performed on the temperature patterns in the cooling roll in accordance with the model. Special changes in the cooling conditions are established that minimize the possible deviation of the finished product quality from given values.

Mathematical model of the heating of a dual-layer plate in a metal–elastomer system during thermal vulcanization of the elastomer

Mathematical model of the heating of a dual-layer plate in a metal–elastomer system during thermal vulcanization of the elastomer

Mathematical model of the heating of a dual-layer plate in a metal-elastomer system during thermal vulcanization of the elastomer

A mathematical model of the heating of an infinite dual-layer plate for analytical calculations of the nonstationary temperature fields of this plate during the course of its entire heating with allowance for various schemes employed to organize the vulcanization of a polymeric coating on the metal was built to establish basic laws governing the heating of articles and to determine the effect of the vulcanization obtained by the elastomeric lining during nonstationary heating. As a basis of the model, it is proposed to use a system of familiar linear heat-conduction equations, each of which describes a temperature function, which is dependent on the coordinates and time. The mathematical software package MathCAD was used to solve the indicated system, beginning with version MathCAD-2000. Here, the relative error of the calculations does not exceed 0.5%.

Sulfur-Free Vulcanization of Modified Butadiene-Acrylonitrile Rubber SKN-40PVKh-30, Aimed To Obtain Elastomeric Materials Resistant to Aggressive Media

A study was made of the thermal, peroxide, and radiation vulcanization of modified butadiene-acrylonitrile rubber SKN-40PVKh-30 in the presence of a polyhalomethyl compound, 1,4-bis[(4-trichloromethylphenyl)dichloromethyl]benzene, with epoxy and phenol-formaldehyde resins and 4,4′-dithiobis-N-phenylmaleimide (a sensitizer) additionally included in the formulation with the aim to improve the technical properties of the vulcanizates and elastomeric materials. The parameters of the three-dimensional network of the vulcanizates were studied by sol-gel analysis; the total number of active chains of the network (1/Mc), number of cross-linked molecules \((1/M_{n_\tau } )\), and gel fraction content were determined for the thermal, peroxide, radiation, and thermoradiation vulcanizates.

ゴム混練中における加硫促進剤の熱履歴とその加硫挙動について(2)

ゴム混練中における加硫促進剤の熱履歴とその加硫挙動について(2)

Thermal Vulcanization of Rubbers at High Pressure

Thermal Vulcanization of Rubbers at High Pressure

Reactions of zinc and magnesium oxides and chlorides in the vulcanization of chloroprene rubbers and in the ageing of vulcanizates

The formation of ZnCl 2 during the vulcanization of polychloroprenes regulated by mercaptans in the presence of ZnO occurs simultaneously with crosslinking reactions as a result of the participation of mobile chlorine in the reaction. In polychloroprenes regulated with sulphur, not less than 50% of the bonds are formed without the participation of chlorine in the reactions. The number of chlorine atoms combined in the form of ZnCl 2 exceeds that corresponding to the concentration of allyl chlorine in the polymer, that is, a different type of mobile chlorine participates in the reactions. The number of transverse bonds found experimentally exceeds the calculated figure obtained with the condition that each bond is formed by one or two atoms of chlorine. The addition of MgO as well as ZnO leads to a reduction in the chlorine participating in the reactions. Metals of the vulcanizing oxides exist in the vulcanizates as oxides, chlorides, sulphides or sulphurous compounds, a fact which does not confirm the suggestion that Zn participates in the formation of transverse valency bonds of the type ROZnOR. ZnCl 2 participates directly in the formation of transverse bonds during the vulcanization of chloroprene rubbers by use of the same reactive sites in the polymeric molecules as those responsible for crosslinking during thermal vulcanization. Crosslinking by an ionic mechanism at double bonds in the 1,4 position does not play any substantial part in the general vulcanization effect. ZnCl 2 inhibits the processes of structure-formation, degradation and oxidation of the polymer during the ageing of chloroprene rubber vulcanizates.

Some features of the vulcanization of butadiene-nitrile rubbers

BUTADIENE-nitrile rubbers are fairly reactive polymers and consequently they can be vulcanized by various methods. I t has been shown previously that they readily undergo thermal vulcanization [1]. Vulcanization also occurs in the presence of hydroxides of alkaline earth metals [2] and zinc chloride [3]. The mechanism of vulcanization and the structure of the vulcanized network are naturally different when different vulcanizing agents arc used [4]. In contrast to SKB* thermal vulcanization of butadiene-nitrile rubbers involves elimination of a hydrogen atom from the carbon atom in the a-position with respect to the nitrile group [5]. The underlying process in vulcanization in the presence of bases is hydrolysis of the nitrile groups and formation of salt bonds [2]. Vulcanization in the presence of zinc chloride, at least in the initial stages, apparently involves complex formation at the nitrilc groups. The scheme of thermal vulcanization put forward in reference [5], which postulates elimination of a hydrogen atom in the a-position with respect to the CN group, reaction of a nitrile group with this carbon atom and formation of intraand intermolecular -CN--C-bonds, is supported by reports on studies of the properties and structure of polyacrylonitrile [6-9] and on the polymerizability of saturated alkyl nitriles [10, ll]. Two additional new experimental facts have provided definite confirmation of this mechanism of thermal vulcanization. SKN-40, which has a fairly high nitrile content, should after thermal vulcanization acquire to some extent semiconducting properties, as occurs with polyacrylonitrile [6-7]. The rubber was extracted with acetone for 80 hr and heated at 183 °, then the change in its electrical conductivity was determined. I t was found that heat t reatment brings about an increase in the specific conductivity from 0.8 X 107 to 0.5 x 106 ohm -1. cm -1,

Radiation chemistry test stand facility for thermal and radiation vulcanization of tires using a spent fuel element irradiator

Radiation chemistry test stand facility for thermal and radiation vulcanization of tires using a spent fuel element irradiator

Vulcanization of some synthetic rubbers without sulphur—IV. The effect of the nitrile-group content on the thermal vulcanization of butadiene-nitrile rubbers

Vulcanization of some synthetic rubbers without sulphur—IV. The effect of the nitrile-group content on the thermal vulcanization of butadiene-nitrile rubbers