Tensile Strength Of Natural Rubber Research Articles

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.

Studies on natural rubber nanocomposites by incorporating amine functionalised graphene oxide

ABSTRACT The present study reports the synthesis of amine functionalised Graphene Oxide by two different methods, one by a modified Bucherer reaction and the other by using dodecyl amine. The synthesised amine functionalised Graphene oxide by modified Bucherer reaction (AGO) and by using dodecyl amine (DGO) was characterised by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Raman spectroscopy. A series of natural rubber (NR)-AGO and NR-DGO nanocomposites with varying compositions of AGO and DGO were prepared by the latex mixing method. The morphological, mechanical, and dielectric properties of the nanocomposites were analysed by SEM, TEM, universal testing machine (UTM), and impedance analyser. The results obtained for NR-AGO and NR-DGO nanocomposites revealed enhancement in mechanical and dielectric properties from neat NR and NR-Graphene Oxide (GO) nanocomposites. The tensile strength of NR has been improved by almost 70%, tensile modulus (300% elongation) by 85%, and tear strength by 67% on the addition of 0.5 phr of AGO and by the addition of 0.5 phr DGO, the tensile strength of NR has been improved by 74%, tensile modulus (300% elongation) by 87% and tear strength by 73%.

Mechanical strength of natural rubber filled fly ash

In this present work, Fly ash was incorporated into natural rubber to form a natural rubber composite. The natural rubber composite was prepared by solution mixing method at the constant amount of fly ash at 80 phr. The fly ash particle was modified its surface by TESPT silane coupling agent before mixing with natural rubber latex. The surface morphology of natural rubber composites were examined by SEM image. The vulcanization parameters were examined by MDR technique. The results show that modified fly ash affects to natural rubber compound by shorten the vulcanization time and increase maximum torque. The mechanical properties were investigated from stress-strain curve. It reveals that the surface modification of fly ash improves tensile strength of natural rubber by 6 times. The increasing of strength may attribute to the formation of polymer-fillers interaction through TESPT molecules.

Features of crystallization behavior of natural rubber/halloysite nanotubes composites using synchrotron wide-angle X-ray scattering

ABSTRACTThe correlation between the mechanical strength and the crystallization behavior of natural rubber (NR)/halloysite nanotubes (HNT) composites is discussed. The tensile strength of NR is improved with the addition of HNT. This improvement is attributed to the unique structure of HNT, which facilitates good dispersion and strong interfacial interaction. HNT also play an important role in assisting the strain-induced crystallization of NR. Crystallization under strain is observed using synchrotron wide-angle X-ray scattering. The stress–strain curves and the corresponding degree of crystallinity after straining provide further evidence. Based on these analyses, a mechanistic model for strain-induced crystallization and the evolution of the orientation of the network structure is proposed.

Highly enhanced mechanical properties in natural rubber prepared with a nanodiamond nanomatrix structure

A nanodiamond nanomatrix structure is formed into natural rubber, generating not only entropic elasticity but also energetic elasticity. The radical reaction with tert-butylhydroperoxide (TBHP)/tetraethylenepentamine (TEPA) in the latex stage forms a chemical linkage between the nanodiamond and natural rubber particles after removing proteins from the rubber. To investigate the relationship between morphology and mechanical properties, the as-cast films prepared from nanodiamond-grafting deproteinized natural rubber (DPNR-ND) latex are subjected to transmission electron microscopy (TEM), tensile tests, and dynamic mechanical analyses. The nanodiamond nanomatrix structure markedly increases the tensile strength of natural rubber. The values of the storage modulus and loss modulus are about ten times higher than those of natural rubber in the rubbery plateau region when DPNR-ND contains 40 w/w% ND. Thus, an energetic elasticity is realized in conjunction with the entropic elasticity.

Reinforcement effect of soy protein nanoparticles in amine-modified natural rubber latex

Mechanical properties of natural rubber reinforced with soy protein nanoparticles are useful for various rubber applications. However, the properties is further improved by improving interactions between soy protein and rubber. A novel method is used to modify particle surface of natural rubber latex by grafting with diallylamine. The improved polymer-filler interactions caused tensile stress at 300% elongation to match that of carbon black, which is a breakthrough for organic fillers. The grafting was demonstrated with infrared and particle size measurements. The size of natural rubber latex particles increased 8% after the grafting and the infrared spectra showed an increase of amine groups in coagulated NR latex. The curing rate of modified NR reinforced with soy protein matches that of carbon black composite. With the addition of 10% soy protein nanoparticles, the tensile strength of natural rubber and modified natural rubbers increased from 9 to 15MPa to 19–25MPa. Both dynamic mechanical strain and swelling measurements indicate modified natural rubber composites have a higher degree of polymer-filler interaction. The change of reinforcement factors with filler fraction can be described by modified Mooney model that includes anisotropic reinforcement elements. Tanδ at 60°C indicates the modified composite has a better rolling resistance than carbon black.

Characterization of electron beam irradiated natural rubber/modified starch composites

The effects of electron beam irradiation on thermal, mechanical and morphological properties of natural rubber/starch blends were investigated. The results of thermogravimetric analysis indicated that the thermal stability of natural rubber was improved by the addition of modified starch and by irradiation. On the other hand, thermal stability of irradiated natural rubber and natural rubber/unmodified starch blends is lower than that of pure natural rubber. The tensile strength of natural rubber (2.01MPa) was improved to 3.82MPa with the addition of 5phr unmodified starch. There was a further increase from 2.01MPa to 6.44MPa when 5phr modified starch was used.

Self-assembled natural rubber/multi-walled carbon nanotube composites using latex compounding techniques

Functionalization of multi-walled carbon nanotubes (MWCNTs) plays an important role in eliminating nanotube aggregation for reinforcing polymeric materials. We prepared a new class of natural rubber (NR)/MWCNT composites by using latex compounding and self-assembly technique. The MWCNTs were functionalized with mixed acids (H2SO 4/HNO 3 = 3:1, volume ratio) and then assembled with poly (diallyldimethylammonium chloride) and latex particles. The Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to investigate the assembling mechanism between latex particles and MWCNTs. It is found that MWCNTs are homogenously dispersed in the natural rubber (NR) latex as individual nanotubes since strong self-aggregation of MWCNTs has been greatly depressed with their surface functionalization. The well-dispersed MWCNTs produce a remarkable increase in the tensile strength of NR even when the amount of MWCNTs is only 1 wt.%. Dynamic mechanical analysis shows that the glass transition temperature of composites is higher and the inner-thermogenesis and thermal stability of NR/MWCNT composites are better, when compared to those of the pure NR. The marked improvement in these properties is largely due to the strong interfacial adhesion between the NR phase and MWCNTs. Functionalization of MWCNTs represents a potentially powerful technology for significant reinforcement of natural rubber materials.

Remarkable reinforcement of natural rubber by deformation-induced crystallization in the presence of organophilic montmorillonite

A remarkable reinforcement of natural rubber (NR) was achieved by adding a low content of organically modified montmorillonite (OMMT). Mechanical tests demonstrated that the most noticeable enhancement in the tensile strength of NR was at a OMMT content of 5 wt.%. In order to gain further insight into the mechanism of reinforcement by OMMT, the deformation-induced crystallization behavior and morphology of NR/OMMT nanocomposites with different OMMT contents were investigated by synchrotron wide angle X-ray diffraction and transmission electron microscopy. The results show that the variation in the degree of strain-induced crystallization is consistent with that of tensile strength. The peak in tensile strength at 5 wt.% OMMT content can be ascribed to the fact that strain-induced crystallization is the essential factor in reinforcement of NR. Further, the nanomorphology of OMMT dispersed in a NR matrix plays a decisive role in the crystallization behavior of NR during deformation. An increase in the exfoliation of OMMT leads to an increase in the promotion of deformation-induced crystallization of NR.

Conformation and deformation of linear macromolecules in concentrated solutions and melts in the self‐avoiding random walks statistics

AbstractA strict statistics of self‐avoiding random walks in the d‐measured lattice and continuous space for intertwining chains in the concentrated solutions and melts was proposed. On the basis of this statistics the thermodynamics of conformation and isothermal and adiabatic deformation of intertwining chains was described. The equation of conformational state has been obtained. It was shown that in the field of chains overlap they are stretched increasing its conformational volume. In this volume there are other chains with the formation of m‐ball. Free energy of a chain conformation does not depend upon the fact, if the chains intertwined or they are isolated in the m‐ball. Mixing entropy is responsible to the chains interweaving in the m‐ball. Dependencies of the conformational radius, free energy, and conformation pressure on respective concentration of polymeric chains have been determined. Using the thermodynamics of intertwining polymeric chains of m‐ball conformational state and also the laws of isotropic media deformation into linear differential form the theoretical expressions for elasticity modules (namely, volumetric volume, Young's module and shift's module) and for the main tensions appearing at the equilibrium deformation of the m‐ball were obtained. Poisson's coefficient is a function only on the Euclidean's space and for the real three‐dimensional space is equal to 3/8. A simple model explaining the tensile strength of the m‐ball by the chains intertwining effect and, thereafter by the loss of the mixing entropy, but not by the chemical bonds breaking was proposed. Calculations of the elastic properties, the main tensions, and tensile strength of natural rubber carried out without using the empirical adjusting parameters are in good agreement with the experimental data. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation and characterization of organoclay‐rubber nanocomposites via a new route with skim natural rubber latex

AbstractSkim natural rubber latex (SNRL) is a protein rich by‐product obtained during the centrifugal concentration of natural rubber (NR) latex. A new method to recover rubber hydrocarbon and to obtain nanocomposites with organoclay (OC) was investigated. The approach involved treatment of SNRL with alkali and surfactant, leading to creaming of skim latex and removal of clear aqueous phase before addition of OC dispersion. Clay mixed latex was then coagulated to a consolidated mass by formic acid, followed by drying and vulcanization like a conventional rubber vulcanizate. X‐ray diffraction (XRD) studies revealed that NR nanocomposites exhibited a highly intercalated structure up to a loading of 15 phr (parts per hundred rubber) of OC. Transmission electron microscopy studies showed a highly exfoliated and intercalated structure for the NR nanocomposites at loadings of 3–5 phr organically modified montmorillonite (OMMT). The presence of clay resulted in a faster onset of cure and higher rheometric torque. The rubber recovered from skim latex had a high gum strength, and a low amount of OC (5 phr) improved the modulus and tensile strength of NR. The high tensile strength was supported by the tensile fractography from scanning electron microscopy. Thermal ageing at 70°C for 6 days resulted in an improvement in the modulus of the samples; the effect was greater for unfilled NR vulcanizate. The maximum degradation temperature was found to be independent of the presence and concentration of OC. The increased restriction to swelling with the loading of OC suggested a higher level of crosslinking and reinforcement in its presence. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3277–3285, 2006

Degradation behaviour of natural rubber–aluminium powder composites: effect of heat, ozone and high energy radiation

Properties such as resistance towards heat, ozone and gamma radiation and flame resistance of aluminium powder filled natural rubber composites were studied. Aluminium powder filled natural rubber composites showed better retention of mechanical properties after thermal ageing compared to other fillers like HAF, GPF, silica and acetylene black. Tensile strength of natural rubber (NR)–aluminium powder vulcanizates increased slightly after ageing for 7 days at 70 °C due to the slow and continued crosslinking, but on prolonged ageing, chain scission predominated, which decreased the tensile strength. These composites also have better resistance towards ozone exposure. The cracks generated due to ozone exposure are small and discontinuous in aluminium powder filled vulcanizates, whereas the cracks are deeper, wider and continuous for other filler incorporated samples. Effects of various bonding agents namely hexamethylene tetramine-resorcinol system (HR), bis [3-(triethoxysilyl) propyl] tetrasulfide (Si-69), cobalt naphthenate (CoN) and toluene diisocyanate (TDI), on the ageing characteristics of natural rubber-aluminium powder composites were studied and it was found that these composites have better resistance towards heat, ozone, and gamma irradiation.

The Role of Oxygen in the Vulcanization of Natural Rubber

Abstract A three-dimensional structure is formed during the vulcanization of rubber. The complex processes of formation, rupture, and regrouping of bonds during vulcanization lead finally to union of the long chain molecules into a compact network. The density of the network formed during vulcanization and the distribution and degree of sulfide formation by the bonds govern to a large degree the work-capacity of vulcanizates. Structure formation in vulcanizates is manifest by the change of their tensile strength, elasticity, swelling, and solubility. During the vulcanization of natural rubber, an optimum is observed in the change of tensile strength and other technically important properties of the material. The decrease of tensile strength of vulcanizates by overvulcanization is usually ascribed to the oxidative destruction of the molecular chains of the rubber. The strong influence which has been observed of oxygen on the tensile strength of natural rubber and its vulcanizates is the basic argument in favor of oxidative destruction. This influence, however, only appears when the rubber is in direct contact with oxygen or air. When, in the rubber industry, vulcanization is carried out in presses, the surface of the rubber mixture is isolated from atmospheric oxygen, and, consequently, destruction in this case can be caused only by the oxygen dissolved in the rubber mixture.

Studies of the Vulcanization of Rubber. III. Kinetics of Change of Tensile Strength of Natural Rubber during Vulcanization

Abstract 1. It is shown that the tensile strength of vulcanized butadiene-styrene rubber is a linear function of the plasticity of the original material. 2. Proceeding from concepts of the presence during vulcanization of a number of opposing processes of structure formation and destruction, both of which influence the molecular weight of the rubber, a general equation is derived which expresses the kinetics of the change of tensile strength of a vulcanizate. 3. Experimental material is offered which proves the applicability of the proposed equation to the representation of the kinetics of vulcanization of mixtures of natural rubber containing relatively small sulfur contents, i.e., up to 3 per cent.

A theoretical analysis of the distribution of tensile strength of vulcanized rubber

AbstractBy means of a mathematical treatment the distributions of the tensile strength of natural rubber and GR‐S were studied. As a result of this study it is shown that the distributions are of the so‐called doubly exponential type.

Determination of Tensile Strength of Natural Rubber and GR-S. Effect of Specimen Size

Abstract Peirce's equation, which relates observed tensile strength of textile fibers with their length, was found to be applicable to rubberlike material if specimen volume is used in place of specimen length. Experiments in which the tensile strengths of GR-S and natural rubber compositions were determined for a range of specimen volumes yielded results in close accord with theory. A tenfold increase in the volume of the material resulted in a decrease of 308 and 339 and of 204 pounds per square inch in the observed tensile strength of GR-S and comparable natural rubber stocks, respectively. The numerical magnitudes of the slopes of the straight lines obtained when tensile strengths were plotted against the logarithms of the relative specimen volumes are shown to bear direct relationships to the homogeneity of the stocks under test. The use of a dumbbell sample with a constricted center should result in a relatively simple means of measuring quantitatively the degree of homogeneity of rubber compositions.

Determination of Tensile Strength of Natural Rubber and GR-S

Determination of Tensile Strength of Natural Rubber and GR-S