Filler Elastomer Research Articles

Infiltration of uncured elastomers into silica agglomerates

AbstractThe degree of impregnation of an agglomerate by the suspending matrix is an important parameter because it influences the agglomerate cohesion and thus has a direct effect on dispersion mechanisms. Penetration kinetics reported in the literature were only measured in Newtonian or not very elastic matrices, although one of the main applications is the dispersion of porous filler in elastomers. The aim of this article is to study the infiltration of porous silica agglomerates by uncured elastomers using optical microscopy. The application of the model of Bohin (infiltration of a Newtonian fluid into a porous sphere) is discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3292–3300, 2004

New Economical Filler for Elastomer Composites

Incorporation of fillers in elastomers results in a profound effect on mechanical properties of the composites formed. Significant study has been carried out on this topic. Fillers are customarily classified into organic and inorganic. The latter class includes calcium carbonate, talc, barium sulphate, china clay (kaolin), magnesium oxide, alumina, silica, etc. Flyash, a waste product of thermal power stations contains inorganic oxides, hence, it was thought that it could be used as filler for elastomers. Flyash is generated in huge quantities every day, posing problems of its disposal. At present, in India, the utilization of flyash is only 3% as opposed to 20–25% in other developed countries. In this work, an attempt is made to use flyash as a filler in elastomer (polybutadiene rubber). The composites were prepared with various percentages of flyash and were subjected to testing for mechanical properties. The results were compared with the composites containing conventional fillers, i.e., calcium carbonate and talc. The results indicated that flyash could be used as a filler or as a supporting filler. The relevance of this study could help in solving the problem of disposal of flyash and, at the same time, the polymer industry will benefit by identifying an economical filler.

Effect of coupling agent on the mechanical properties of fly ash–filled polybutadiene rubber

AbstractFly ash, a waste productof thermal power stations generated in huge quantities, has been posing problems of its disposal. As such it contains a variety of inorganic oxides and is available in finely powdered form. Attempts have been made for its use as a filler in elastomers and plastics. It is important to note that fly ash used in in untreated form does not significantly enhance the mechanical properties of composites. In this work, fly ash treated with silane coupling agent (Si‐69) was used as a filler in polybutadiene rubber (PBR). The comparison of properties of composites filled with treated and untreated fly ash revealed that the composites with treated fly ash showed better reinforcing properties. Thus the silane coupling agent used here promoted adhesion between fly ash and the PBR. The improvement in mechanical properties in general and tensile properties (tensile strength, modulus 100% and modulus 200%, hardness) of the composites in particular were observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1322–1328, 2004

Reinforcement of model filled elastomers: characterization of the cross-linking density at the filler–elastomer interface by 1H NMR measurements

The cross-linking density at the filler–elastomer interface is analyzed by 1H NMR measurements in model reinforced elastomers composed by grafted nanosilica particles and cross-linked ethylacrylate chains. We have focused our attention on the effect of introducing fillers on the relaxation of the bulk polymer matrix which is observed at long times (t>100μs). Measurements performed at high temperature (T>Tg+120K) have revealed that its relaxation is affected by the topological constraints existing at the particle surface. We deduce that the effect of particles in the bulk matrix can be interpreted as that of an homogeneous additional constraint density which increases proportionally to the surface area introduced in the matrix.

Dynamics of Nanoparticle Chain Aggregates of Carbon Under Tension

AbstractCarbon black in the form of nanoparticle chains is used as a reinforcing filler in elastomers. However, the dynamics of the filler particles under tension and their role in the improvement of the mechanical properties of rubber are not well understood. We have studied experimentally the dynamics of isolated nanoparticle chain aggregates (NCAs) of carbon made by laser ablation, and also that of carbon black embedded in a polymer film. In situ studies of stretching and contraction of such chains in the transmission electron microscope (TEM) were conducted under different maximum values of strain. Stretching causes initially folded NCA to reorganize into a straight, taut configuration. Further stretching leads to either plastic deformation and breakage (at 37.4% strain) or to a partial elastic behavior of the chain at small strains (e.g. 2.3% strain). For all cases the chains were very flexible under tension. Similar reorientation and stretching was observed for carbon black chains embedded in a polymer film. Such flexible and elastic nature of NCAs point towards a possible mechanism of reinforcement of rubber by carbon black fillers.

Filler–elastomer interactions: influence of oxygen plasma treatment on surface and mechanical properties of carbon black/rubber composites

In this work, the influence of oxygen plasma treatment on the surface and adsorption properties of carbon blacks was investigated using X-ray photoelectron spectroscopy (XPS), ζ-potential, and BET isotherms. Then the mechanical properties [tensile strength and tearing energy ( G IIIC)] of carbon black/acrylonitrile butadiene rubber (NBR) composites were measured. As a result, it was found that oxygen plasma treatment generated oxygen-containing functional groups, such as, carboxyl, hydroxyl, lactone, and carbonyl groups, on the carbon black surfaces, resulting in a decrease in the equilibrium spreading pressure or London dispersive component of surface free energy. The tearing energy of the carbon black/NBR composites improved as the oxygen-containing functional groups on the carbon black surfaces increased. This revealed that there is a relatively high degree of interaction between the polar NBR and the oxygen-functional groups of carbon blacks.

Filler–elastomer interaction in model filled rubbers, a 1H NMR study

1H NMR experiments on filled rubbers allow the observation of two features: the introduction of supplementary topological constraints by the fillers, and a layer of immobilised segments at the particle surface. In order to assess the role of the filler–elastomer interaction on the local chain dynamics, silica filled elastomer model systems were prepared. The synthesis methods used allowed us to test vastly different interaction strengths. It is shown that in the case of a weak interaction, the influence of the fillers is small, whereas a strong anchoring at the interface leads to an increase in the density of the topological constraints. The latter is correlated to a layer of highly immobilised segments whose thickness decreases with temperature. This layer is seen as a glassy shell.

The scale behavior of fillers in elastomers by means of indentation tests

Indentation tests were carried out on a carbon black filled rubber sample on different length scales. The experiments covered the range from aggregation of particles on the submicron scale up to structures which represent the bulk properties of the sample on the millimeter scale. The local stiffness was used to visualize the areas investigated; therefore, mechanical images were obtained for all length scales. So-called “mechanical units” were defined for every scale. The size distribution curves for the mechanical units were analyzed and they were found to be non-Gaussian-shaped for every scale. Moreover, the distribution curves of the mechanical units are similar to the distribution curves of particles and aggregates obtained by electron microscopy reported in the literature. Evaluation by means of fractal analysis led to fractal dimensions for the mechanical units. It could be shown in the present case that the fractal dimension D≈1.24 of the mechanical units in the range of submicrons up to several hundred microns is in good agreement with that of the filler aggregates proposed in the literature. Furthermore, D is constant over a wide range of about 6 decades in area scale starting from aggregates up to the size of agglomerates. This leads to the conclusion that the local arrangement of the filler ensembles seems to be self-similar from the smallest scale of aggregation of particles up to the largest formation observed by indentation testing on the millimeter scale.

High-Resolution Solid State NMR Investigation of the Filler-Rubber Interaction: Part III. Investigation on the Structure and Formation Mechanism of Carbon Gel in the Carbon Black-Filled Styrene—Butadiene Rubber

Abstract This investigation describes the elastomer—filler interaction and its formation mechanism using solid state high-resolution, high-speed 1H magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. Pulsed NMR measurements were carried out on pure styrene-butadiene rubber (SBR), and solvent extracted carbon gels from freshly prepared and storage matured master batches. The effects of filler loading, storage maturation, severity of extraction and experimental temperature on the elastomer-filler interaction were examined and discussed. High resolution in NMR was achieved by higher temperature/low spinning rate, room temperature/high spinning and combined rotation and multiple-pulse spectroscopy (CRAMPS) techniques. High-speed magic-angle spinning (MAS) was found to be the most suitable method to achieve high resolution. Proton spin—spin relaxation time, T2, was measured successfully for each of the principal resonance species present in the samples. These measurements reveal an insight into the site-specific nature of the polymer—filler interaction. The relative immobilization of the dynamics of different protons, due to the presence of carbon black filler, and their temperature dependence evidence that the main chain vinyl proton is the most significantly immobilized one compared to the aromatic and methylene species. The effects of storage maturation and severity of extraction on the dynamics of the conformational jump have also been discussed. This work clearly demonstrates the importance of unsaturation on the bound rubber formation. It also provides first direct physical evidence confirming the hypothesis that bound rubber variation during the storage maturation is due to slow progressive replacement of short rubber chains by larger ones.

High‐resolution solid‐state NMR investigation of the filler–rubber interaction: 2. High‐speed [1H] magic‐angle spinning NMR spectroscopy in carbon‐black‐filled polybutadiene

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer–filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. Three series of samples were compared: pure polymers, raw polymer–filler blends (filler loading ratio: 50 phr) and solvent-extracted blends (so as to get rid of any polymer which is not under the influence of the solid surface). While differential scanning calorimetry points to the existence of an elastomer fraction which is not detected as undergoing the glass transition, ie is strongly immobilized, [1H] high-resolution high-speed magic-angle spinning solid-state NMR provides information on the effect exerted by polymer–filler interactions on the mobility of the various constitutive species of the macromolecular backbone. A systematic study of the evolution of the spectral lines yielded by the samples indicates that 1,2-polybutadiene moieties have a particular affinity towards the carbon black surface which suggests the occurrence of specific interactions at the elastomer–filler interface. © 2001 Society of Chemical Industry

Microcharacterization and identification of tire debris in heterogeneous laboratory and environmental specimens

Tire debris is produced by the normal wear of tires. Two problems are addressed herewith: characterization of debris particles and their identification in heterogeneous specimens, which come from laboratory wear tests and from the environment. Both problems are solved by analytical electron microscopy (EM). The scanning electron microscope (SEM) shows that tire debris has a typical, warped surface and pores, and that its characteristic elements, detected by energy dispersive X-ray spectroscopy (EDXS), are S and Zn. As a consequence, the identification of tire debris particles in heterogeneous laboratory specimens is straightforward. In those environmental specimens (road dust), where Zn cannot be detected, identification is possible in some cases, provided morphology, microanalysis, and X-ray mapping are combined. The analytical transmission electron microscope characterizes tire debris on the sub-micrometer scale by imaging, EDXS, and electron diffraction patterns. The microstructure exhibits typical elastomer–filler clusters. The representative elementary volume is found to be approximately 8×10 −23 m 3.

High‐resolution solid‐state NMR investigation of the filler–rubber interaction: 2. High‐speed [1H] magic‐angle spinning NMR spectroscopy in carbon‐black‐filled polybutadiene

AbstractThis work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer–filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. Three series of samples were compared: pure polymers, raw polymer–filler blends (filler loading ratio: 50 phr) and solvent‐extracted blends (so as to get rid of any polymer which is not under the influence of the solid surface). While differential scanning calorimetry points to the existence of an elastomer fraction which is not detected as undergoing the glass transition, ie is strongly immobilized, [1H] high‐resolution high‐speed magic‐angle spinning solid‐state NMR provides information on the effect exerted by polymer–filler interactions on the mobility of the various constitutive species of the macromolecular backbone. A systematic study of the evolution of the spectral lines yielded by the samples indicates that 1,2‐polybutadiene moieties have a particular affinity towards the carbon black surface which suggests the occurrence of specific interactions at the elastomer–filler interface.© 2001 Society of Chemical Industry

The effect of surface modification on physicochemical properties of precipitated silica

The main goal of this study was to obtain hydrophobic silica whose properties would allow their application as plasto- and elastomer fillers. Thus, hydrated silica was modified by silane and titanate coupling agents. The modification procedure and appropriate modification apparatus were developed. The degree of silica surface modification was evaluated by different methods. As grounds for this evaluation, changes in the physicochemical properties, brought about by the condensation reaction of surface silanol groups with alkoxyl or hydroxyl groups of the molecules of coupling agents, were used. The degree of hydrophobicity of the silica surface was determined on the basis of the heat of immersion of this surface, and silanol groups were identified by the infrared spectroscopy. Moreover, changes in the tendency to form agglomerates and aggregates of molecules were studied by microscopy. It was found that modification with silane and titanate coupling agents leads to an increase in silica activity. Application of these agents results in the change of the hydrophilic character to the hydrophobic one.

PP-elastomer-filler hybrids. I. Processing, microstructure, and mechanical properties

Three-component systems with a polypropylene (PP) matrix consisting of polar elastomer (ethylene–propylene rubber and styrene–ethylene–butylene–styrene grafted with maleic anhydride) or of polar PP (PP grafted with maleic anhydride) and filler were investigated. Three microstructures of PP–elastomer–filler hybrids were obtained by processing control and elastomer or PP modification with the maleic anhydride: fillers and rubber particles were separated in the PP matrix, rubber particles with filler core were distributed in the PP matrix, and mixed microstructures of the first and second. A study of mechanical properties showed that the elastic modulus increased in the first microstructure and impact strength increased in the second microstructure. Mechanisms for the relationships between microstructure, processing, and mechanical properties are discussed. © 1996 John Wiley & Sons, Inc.

Effect of Ionizing Radiation on the Properties of Ultrahigh Molecular Weight Polyethylene Fibers

Ultrahigh molecular weight polyethylene UHMW-PE fibers intended to be used as reinforcing fillers in elastomers were subjected to ionizing radiation vulcanization to avoid the deleterious effect of conventional sulfur vulcanization conditions, i.e., vulcanization temperature on the properties of polyethylene fibers. Thus, UHMW-PE fibers (Spectra™ 1000) were subjected to both gamma as well as electron beam radiation in absence of air and up to 250 kGy. Changes in melting (Tm) and crystallization temperature (Tc) enthalpy of melting and crystallization depending on the type and dose of radiation were followed up using differential scanning calorimetry (DSC). In addition to the observed decrease in tensile strength, decrease in fiber diameter and increase in modulus depending on radiation dose were correlated with the changes in fiber morphology.

Modification estimate of kaolin, chalk, and precipitated calcium carbonate as plastomer and elastomer fillers

Investigation into possible modifications of surfaces of white fillers such as Kornica chalk, precipitated calcium carbonate and KOG Kaolin. The surfaces of these fillers were modified with a variety of proadhesive compounds in different amounts. Optimum proadhesive compound was determined for each kind of filler. The modified fillers were tested in rubber mixtures based on butadiene-styrene rubber and in polyurethanes.

Polymer–filler interaction in polyurethane kraft lignin polyblends

AbstractKraft lignin fillers have been shown to enhance the mechanical characteristics of different types of polymeric‐based sealants; however, the mechanism for reinforcement and the degree of interaction was not well understood. In this study, interactions between a polyurethane‐based elastomer and various Kraft lignin fillers as well as kaolin and titanium dioxide filler combinations were investigated in an effort to determine the most useful elastomer–filler combination for use as a construction joint sealant. A relationship that describes and relates the characteristics of polymer–filler interaction requires that the surface‐energy properties of both the polymer matrix and the filler be determined. Measurements using the sessile drop method are used to evaluate the critical surface energy of the polymer matrix, whereas the rate of rise of a liquid through a bed of filler provides the means to evaluate the surface energetics of the various fillers. Results obtained from this study show that the tensile modulus of the different elastomer formulations are proportional to the equilibrium work of adhesion, as described by the relationship derived by Lee that relates the degree of interaction of the formulation components and the mechanical properties of the blends. © 1994 John Wiley & Sons, Inc.

Filler—Elastomer Interactions. Part IX. Performance of Silicas in Polar Elastomers

Abstract Inverse gas—solid chromatography of silicas showed that the free energies of adsorption of polar probes were much higher than those obtained with n-alkanes. This implies that polymer—silica interaction is more pronounced in polar rubbers than in nonpolar rubbers such as polybutadiene. Using a series of silica and carbon-black-loaded acrylonitnle—butadiene (NBR) compounds with different acrylonitrile (ACN) content, this paper shows the changes in viscoelastic properties of the silica compounds can be attributed to improved polymer—filler interactions relative to the interactions involved in carbon-black compounds.

Properties of precipitated silicas as elastomer fillers

Properties of precipitated silicas as elastomer fillers

Dielectric characteristics of static shield for coil-end of gas-insulated transformer

The impulse breakdown characteristics of insulation models simulating static shields for coil ends of SF/sub 6/ gas-insulated transformers are studied. The static shield is composed of a double-covered electrode and a filler between the coverings. If a filler made of elastomer material is fitted closely on the covered electrode to eliminate gas gaps between the filler and the covered electrode, the impulse breakdown voltage of the static shield is higher than with gas gaps. If a low-permittivity filler is used, the impulse breakdown voltage of the static shield is still higher. The breakdown voltage can be explained by considering that the breakdown is caused by small gas gaps between the filler and the covered electrode. The dielectric strength of the coil end can be increased by applying a static shield with an elastomer filler.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>