共混硫化丁腈橡胶-氯丁橡胶的物理性能

将丁腈橡胶(NBR)和氯丁橡胶(CR)按不同质量分数共混并硫化,研究了硫化橡胶在自然环境、热空气老化、热油老化等条件下的物理性能,并测定了硫化橡胶与镀铜钢丝的粘合性能.结果表明,随着CR质量分数的增大,混炼胶的焦烧时间逐渐缩短.经热空气老化后,NBR的硬度增加幅度比CR的硬度增加幅度大,拉断强度降低幅度则比CR的小得多.此外,NBR的耐油性能优于CR.就物理性能以及与镀铜钢丝的粘合性能而言,单一NBR和单一CR优于共混NBR/CR.     

Thermal properties in cured natural rubber/styrene butadiene rubber blends

Blends of natural rubber (NR) and styrene butadiene rubber (SBR) were prepared with sulfur and n-t-butyl-2-benzothiazole sulfonamide (TBBS) as accelerator, varying the amount of each polymer in the blend. Samples were analysed by rheometer curing at 433 K until their maximum torque was reached. The miscibility among the constituent polymers of the cured compounds was studied in a broad range of temperatures by means of differential scanning calorimetry, analyzing the glass transition temperatures of the samples. The specific heat capacity of the compounds was also determined. Thermal diffusivity of the samples was measured in the temperature range from 130 to 400 K with a new device that performs measurements in vacuum. The thermal results are explained on the basis of the structure formed during the vulcanization of the samples considering the variation of the crosslink density of each phase. Finally, a serial thermal conduction model that takes into account the contribution of each phase to the thermal diffusivity was used to fit the experimental results.     

Colloidal properties of rubber latex

Summary This work describes the dialysis, the determination of the total soap content in the latex system by conductometric titration, the effect of dilution on soap distribution between the aqueous and polymer phases, the confirmation of the average diameter of the latex particles, the electrophoretic behavior, and the establishment of the solids content below which the latex behaves according toBeer's law for the transmission of light. The colloidal system used in this study was a styrenebutadiene ( 11) latex (Naugatex 2740) with potassium salt of the disproportionated rosin (Dresinate 214) as emulsifier.

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Zusammenfassung An einem Styrol-Butadien (11)-Latex (Naugatex 2740) mit dem Kaliumsalz von disproportioniertem Harz (Dresinate 214) als Emulgator wurden folgende Untersuchungen durchgeführt: Dialyse, konduktometrische Bestimmung der Gesamtkonzentration an Seife im Latex, Einfluß der Verdünnung auf die Verteilung der Seife zwischen wässeriger und polymerer Phase, Ermittlung des mittleren Durchmessers der Partikel und elektrophoretisches Verhalten. Weiterhin wurde noch festgestellt, bis zu welchem Feststoffgehalt dasBeersche Gesetz für die Latexssuspension gilt.

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Supported by the U.S. Army Research Office (Durham), Grant No. DA-ARO(D)-31-124-G 656.

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Part of a Ph. D. Thesis byC. G. Force.     

Thermal properties of compatibilized and filled natural rubber/acrylonitrile butadiene rubber blends

The thermal behaviour of natural rubber/acrylonitrile butadiene rubber (NR/NBR) was studied using thermogravimetry (TG) and differential scanning calorimetry (DSC) in terms of blend ratio, crosslinking systems, fillers and compatibilizer (neoprene) were analyzed. The presence of NBR markedly increases the thermal stability of their blends and it lies in between NR and NBR. DSC studies revealed the thermodynamic immiscibility of the NR/NBR blends by the presence of two distinct glass transition temperatures and the immiscibility was prominent even in the presence of a compatibilizer.     

Morphology and properties of natural rubber with nanomatrix of non‐rubber components

The morphology of natural rubber was observed by transmission electron microscopy. Nanomatrix of non‐rubber components such as proteins and phospholipids was found to be inherently formed in natural rubber, in which natural rubber particles of about 0.5 µm in average diameter were dispersed. The nanomatrix of non‐rubber components disappeared after deproteinization of natural rubber with urea. Stress at break of serum rubber was higher than that of deproteinized natural rubber, while strain at break did not change. When the amount of the non‐rubber components increased, the stress at break became significantly dependent upon the amount of non‐rubber components. Viscoelastic properties of natural rubber were also dependent upon the nanomatrix of non‐rubber components. Storage modulus of natural rubber increased significantly, when the amount of the non‐rubber components increased. Copyright © 2010 John Wiley & Sons, Ltd.     

Measurement of rubber properties for design

The rubber properties required for the design of engineering components are primarily concerned with stiffness, although factors such as strength and ageing resistance must be taken into account in materials selection. Calculation of static behaviour requires a shear modulus at the appropriate strain. In order to allow for the strain dependence of the shear moduli of filled rubbers, it is preferable to measure moduli over a range of strains rather than to rely on a single point measurement.

For the purposes of vibration isolation, the stiffness of the rubber is a function not only of frequency but also of the amplitude of the vibration. To allow for this, the shear moduli of the rubber at low strains, of the order of 1%, are required, over a range of frequencies.     

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

The morphology and mechanical and viscoelastic properties of a series of blends of natural rubber (NR) and styrene butadiene rubber (SBR) latex blends were studied in the uncrosslinked and crosslinked state. The morphology of the NR/SBR blends was analyzed using a scanning electron microscope. The morphology of the blends indicated a two phase structure in which SBR is dispersed as domains in the continuous NR matrix when its content is less than 50%. A cocontinuous morphology was obtained at a 50/50 NR/SBR ratio and phase inversion was seen beyond 50% SBR when NR formed the dispersed phase. The mechanical properties of the blends were studied with special reference to the effect of the blend ratio, surface active agents, vulcanizing system, and time for prevulcanization. As the NR content and time of prevulcanization increased, the mechanical properties such as the tensile strength, modulus, elongation at break, and hardness increased. This was due to the increased degree of crosslinking that leads to the strengthening of the 3‐dimensional network. In most cases the tear strength values increased as the prevulcanization time increased. The mechanical data were compared with theoretical predictions. The effects of the blend ratio and prevulcanization on the dynamic mechanical properties of the blends were investigated at different temperatures and frequencies. All the blends showed two distinct glass‐transition temperatures, indicating that the system is immiscible. It was also found that the glass‐transition temperatures of vulcanized blends are higher than those of unvulcanized blends. The time–temperature superposition and Cole–Cole analysis were made to understand the phase behavior of the blends. The tensile and tear fracture surfaces were examined by a scanning electron microscope to gain an insight into the failure mechanism. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2189–2211, 2000     

A novel method for contact analysis of rubber and various surfaces using micro-computerized-tomography

The experimental analysis of the contact state in a tribosystem is of great importance in the study of contact mechanics. In order to make a realistic analysis on the micro scale, it is desirable to keep the tribosystem unperturbed, i.e., without any surface treatment or incorporation of a third body to facilitate the analysis. This study presents the use of a novel technique, micro-computerized tomography (micro-CT), in the investigation of contact between rubber compounds and various counter-surfaces. The goal of this study was to further advance the use of micro-CT in contact mechanics. Specific image analysis techniques were developed in order to process micro-CT images of contact pairs formed by rubber compounds of different hardness levels against counter-surfaces with varying surface roughness and mechanical properties. The micro-CT method has been shown to allow the direct visualization and precise quantification of the real area of contact without altering the original characteristics of the contact pair.     

Effects of rubber type on the curing and physical properties of silica filled rubber compounds

As environmental regulations are getting stricter, tire industries for automobiles have shown much interest in substituting silica for conventional carbon black partially or entirely. To take full advantage of silica as fillers for rubbers, it is essential to find a reasonable rubber system that shows an excellent performance with silica reinforcement. Therefore, in this study, several different rubber compounds comprising the same amount of silica were prepared with several different rubber systems, respectively. The processability, curing characteristics, and mechanical and viscoelastic properties of the rubber compounds were investigated to analyze the performance of the rubber compounds as tire tread materials. Among the rubber compounds studied, SBR1721 compound comprising natural rubber (NR) and styrene butadiene rubber (SBR) with high styrene content was considered the most appropriate for application to tire tread materials. Copyright © 2008 John Wiley & Sons, Ltd.     

Dielectric properties of thermally degraded chloroprene rubber

We performed dielectric measurements on thermally aged carbon-black-filled chloroprene rubber (CR). Primary and secondary processes were observed in unaged and thermally aged CR. The primary process is due to the cooperative motion of chloroprene chains in CR, and the secondary process is due to the local motion of chloroprene chains. For the primary process, the relaxation time slightly increases and symmetric shape parameter of the loss spectrum decreases with increasing aging time. For the secondary process, the relaxation strength decreases with increasing aging time, and reaches zero after 50 h. These changes in the dielectric relaxation parameters are due to the progress of the dehydrochlorination reaction at the chloroprene chains.     

Mechanical properties of natural rubber vulcanizates in finite deformation

Mechanical properties of four kinds of natural rubber vulcanizates differing in vulcanization conditions, and consequently in degree of crosslinking (having values of the Mooney-Rivlin constant C₁ ranging from 0.68 to 1.98) were observed under orthogonal biaxial stretching in a range of strain invariants I_i from 3.4 to 9.0 (extension ratios λ_i from 0.7 to 3.0). The results obtained were analyzed by two methods. One method employed the Valanis-Landel postulate that the strain-energy function W(λ₁, λ₂, λ₃) is a separable symmetric function of the principal extension ratios, i.e., W(λ₁,λ₂,λ₃) = w(λ₁) + w(λ₂) + w(λ₃); the other utilized the contour plots of ?W(I₁, I₂)/?I₁ and ?W(I₁, I₂)/?I₂ surface within the (I₁, I₂) domain. The postulate for W was examined in detail with good agreement with experimental results. The dependences of ?W(I₁, I₂)/?I₁ and ?W(I₁, I₂)/?I₂ surfaces on the degree of crosslinking and temperature were further investigated, with the following conclusions. The surfaces have fairly steep slopes for the region of relatively small deformation (i.e., I₁ < 5) and become flat with increasing I_i for all the test specimens. The slope becomes less steep with decreasing degree of crosslinking. The values of ?W/?I₁ increase linearly and the ?W(I₁,I₂)/?I₂ surface becomes flat, both with increasing temperature: i.e., the temperature dependence of ?W/?I₁ further depends on I_i. The ?W(I₁,I₂)/?I₂ surface has a maximum near 40°C.     

Network structure and mechanical properties of allophanate-cured polyurethane rubber

An allophanate-cured polyurethane (PU) has been prepared. The relationship between trifunctional network structure and mechanical properties is discussed. Mooney-Rivlin constants C₁ and C₂ are determined from stress-strain isotherms. C₂ is approximately constant. The average value of structure factor A₃ in the limit at large deformation is 0.432, in fair agreement with the theoretical prediction of 1/3. The structure factor A′₃ of all PU samples becomes roughly unity in the limit at small deformation. The experimental results are interpreted by the recent Flory theory (a fluctuation-constraint model of junctions). The κ parameter decreases with increasing crosslink density; the ξ parameter is small and approaches zero. Increasing crosslink density tends to cause phantom deformation for extended PU networks. However, the absolute value of the reduced stress in the limit at large deformation (or for the equivalent phantom network) [f] is believed to be overestimated for PU networks with high crosslink density. The origin of this behavior is discussed in detail.     

Thermal properties of swollen butadiene-acrylonitrile rubber vulcanizates

The present paper discusses the results of assessing thermal properties of nitrile rubber, Perbunan NT 3945 and its peroxide vulcanizates, before and after their swelling in solvents such as benzene, toluene and dimethylformamide. The measurements were carried out by means of differential scanning calorimetry (DSC) and thermogravimetry (TG) under nitrogen. It has been found that a slight rise in the glass transition temperature due to the elastomer cross-linking is clearly revealed under the influence of its vulcanizates swelling in solvents whose solubility parameters considerably differ from the solubility parameters of the polymer. The thermal curves of swollen samples reveal processes resulting from polymer-solvent interactions and thermodesolvation processes, which accompany the initial stage of solvent evaporation.The authors would like to express their thanks to the Bayer company for providing free of charge samples of Perbunan NT 1845 and Perbunan 3945 which were used in this study.     

Preparation and properties of natural rubber/rectorite nanocomposites

Natural rubber (NR)/rectorite nanocomposite was prepared by co-coagulating NR latex and rectorite aqueous suspension. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) were employed to characterize the microstructure of the nanocomposite. The results showed that the nanocomposite exhibited a higher glass transition temperature, lower tan δ peak value and slightly broader glass transition region compared with pure NR. The gas barrier properties of the NR/rectorite nanocomposites were remarkably improved by the introduction of nanoscale rectorite because of the increased tortuosity of the diffusive path for a penetrant molecule. The nanocomposites have a unique stress-strain behavior due to the reinforcement and the hindrance of rectorite layers to the tensile crystallization of NR.     

Preparation and properties of nanocomposites based on acrylonitrile–butadiene rubber,styrene–butadiene rubber,and polybutadiene rubber

Nanocomposites were prepared with different grades of nitrile rubber with acrylonitrile contents of 19, 34, and 50%, with styrene–butadiene rubber (23% styrene content), and with polybutadiene rubber with Na‐montmorillonite clay. The clay was modified with stearyl amine and was characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies showed an increase in the gallery gap upon the modification of the filler by stearyl amine. The intercalation of the amine chains into the clay gallery gap was confirmed by the presence of some extra peaks (2928, 2846, and 1553 cm^?1) in the FTIR spectra. The clay–rubber nanocomposites were characterized by TEM and XRD. The mechanical properties were studied for all the compositions. An improvement in the mechanical properties with the degree of filler loading up to a certain level was observed. The changes in the mechanical properties, with changes in the nature and polarity of the rubbers, were explained with the help of XRD and TEM results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1573–1585, 2004     

Effect of rubber on properties of nylon-6/unmodified clay/rubber nanocomposites

Three nylon-6/unmodified clay/rubber nanocomposites with high toughness, high stiffness, high heat resistance and reduced flammability were studied in this paper, on basis of three compound powders of ultra-fine full-vulcanized powdered rubber (UFPR)/montmorillonite (UFPRM). It was found that all of the three UFPRs used in the study can help the silicate layers without organic treatment to be exfoliated in the nylon-6 matrix, despite some differences in compatibilities between them and nylon-6. Accordingly, the clay in different UFPRMs at the same loading content can lead to a similar improvement in stiffness and heat resistance of nanocomposites. In other words, UFPRs having different compatibilities with nylon-6 do not affect the stiffness and heat resistance of nanocomposites largely. However, the nylon-6 nanocomposites, modified with different UFPRMs, show different superior properties. Butadiene styrene vinyl-pyridine UFPRM (VP-UFPRM) is more effective in improving toughness of nylon-6. Nylon-6/silicone UFPRM (nylon-6/S-UFPRM) nanocomposite exhibits more reduced flammability, good flowability and high thermal stability. As for nylon-6/acrylate UFPRM (nylon-6/A-UFPRM) nanocomposite, it shows high toughness and thermal stability. Furthermore, the mechanism of unmodified clay exfoliation during the melt compounding and the effect of different UFPRs on the properties of the nylon-6/UFPRM nanocomposites are also discussed.     

Effect of non‐rubber components on the mechanical properties of natural rubber

Effect of the nanomatrix structure on mechanical properties of natural rubber was investigated in relation to the strain‐induced crystallization. Structure of natural rubber was analyzed through Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction measurement and transmission electron microscopy. The nanomatrix of the non‐rubber components was found to be inevitably formed in natural rubber, in which natural rubber particles linking to fatty acids were dispersed in the nanomatrix of the proteins and phospholipids. The nanomatrix disappeared after deproteinization of natural rubber with urea. Tensile strength and modulus of natural rubber were reduced by removal of the fatty acids and the proteins, which resulted in disappearance of the nanomatrix structure. The effect of fatty acids on the crystallization of natural rubber in small particles as a dispersoid was proved by tensile test of blend of natural rubber and styrene butadiene rubber. Copyright © 2016 John Wiley & Sons, Ltd.     

Research on high temperature friction properties of PTFE/Fluorosilicone rubber/silicone rubber

Silicone rubber (MVQ) has excellent heat resistance, but poor high temperature friction stability, which limits its application in the field of high temperature sealing. Polytetrafluoroethylene (PTFE) is self-lubricating, but its compatibility with rubber is relatively weak. In order to improve the high-temperature friction property of silicone rubber, fluorosilicone rubber (FVMQ) was used as a compatibilizer, and PTFE was added to MVQ by mechanical blending. The friction and wear properties of PTFE/FVMQ/MVQ composites at different temperatures were studied. The results show that compared with MVQ, the mechanical properties of PTFE/FVMQ/MVQ composites was basically unchanged, the coefficient of friction was hardly affected by temperature, and the amount of wear decreased with increasing temperature. PTFE/FVMQ/MVQ composites showed excellent high-temperature abrasion resistance. The high-temperature wear mode was mainly changed from abrasive wear to adhesive wear. The molten layer formed by high-temperature friction can prevent air from directly contacting the surface rubber, which inhibited rubber surface oxidation reaction process.