Swelling Of Rubber Research Articles

Thermal ageing, degradation and swelling of acrylate rubber, fluororubber and their blends containing polyfunctional acrylates

The thermal ageing and degradation behaviour of acrylate rubber (ACM) fluoroelastomer (FKM), and blends of ACM and FKM containing polyfunctional acrylates were studied in air and nitrogen atmospheres. The blends were also subjected to swelling in different solvents. Thermogravimetric analysis of the blends containing polyfunctional acrylate indicated higher thermal stability of the blends by shifting initiation of degradation to higher temperature. The ageing and degradation of FKM-containing blends resulted in elimination of hydrogen fluoride and formation of some lower molecular weight components. Polyacrylates with higher functionality showed multi-step degradation. Higher levels of polyacrylate in the blend resulted in an additional step of degradation compared to polyacrylate. Swelling studies indicated higher swelling resistance of ACM and FKM containing polyacrylate in solvents having different solubility parameters. Maximum swelling of the blends was observed with the solvents having solubility parameter values comparable to that of blends i.e. in the range of 9–10 MPa 1/2. The swelling index of the blends decreased with increasing level of polyfunctional acrylates. Higher functionality of polyfunctional acrylates decreased the swelling index.

Parameters affecting the determination of transport kinetics data in highly swelling polymers above Tg

Sorption and desorption data for n-hexane–natural rubber and n-hexane–low-density polyethylene were analysed to reveal the cause of the s-shaped sorption curves frequently occurring in highly swollen polymers. The model permitted the influence of solute-concentration-dependent diffusivity, sample geometry, boundary concentrations and swelling-induced mechanical stresses on the transport data to be examined. The calculated solute diffusivity varied by several orders of magnitude, depending on the choice of parameters included in the model. The inclusion of direct mechanical stress relaxation parameters only gave a slight improvement of the fit to the experimental data. The inclusion of a time-dependent surface concentration was the only way to fit the s-shaped sorption curves for both natural rubber and low-density polyethylene. Although isotropic three-dimensional swelling of natural rubber occurred over the whole sorption transient period, this condition was unable to explain the swelling (thickness increase) of low-density polyethylene. In the latter system, a model consisting of two stages had to be adopted: stage I where the swelling was mainly one-dimensional, and stage II which occurred later and was characterized by three-dimensional swelling similar to that occurring in natural rubber. During the transient sorption period, the ratio between natural rubber and low-density polyethylene of the ratio of the thickness to cross-sectional area was close to their bulk modulus ratio, which suggests that it is the bulk modulus rather than the Young's modulus which determines the sorption characteristics of polymers above T g.

Phase equilibria of supercritical fluid–polymer systems

Sorption and swelling of silicone rubber (SR), polyisobutylene (PIB), polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), and polyethylene terephthalate (PET) in the presence of sub- and supercritical carbon dioxide have been measured at pressures up to 30 MPa at 308.2 and 323.2 K. Rubbery polymers (SR and PIB) and PMMA showed a sigmoidal increase in sorption with pressure, while other glassy polymers such as PS and PC and a crystalline polymer, PET, showed the monotonic increase/level-off sorption behavior. The well-known dual-mode sorption mechanism was found to be inadequate to describe the sorption behavior of glassy polymers at high pressures. The amount of sorption was successfully calculated from the experimental swelling data for SR. Density representation of sorption was much better than the pressure representation. Other sorption and swelling behaviors have also been analyzed and discussed.

Viscoelasticity and Kinetics of Wetting on Rubber

Abstract The kinetics of spreading of a liquid drop is usually controlled by conversion of capillary potential energy into viscous dissipation within the liquid when the solid is rigid. However, if the solid is soft, a “wetting ridge” near the solid/liquid/vapour triple line can also be a dissipative sink as the wetting front moves. As a consequence, the kinetics of wetting of rubber may be controlled essentially by viscoelastic losses in the polymer rather than by viscous losses in the liquid drops. Therefore, a direct analogy between the kinetics of wetting and adhesion, respectively, for a liquid and a solid on an elastomeric substrate has been recently proposed. In this paper, the superposition of viscoelastic braking and moderate rubber swelling in the drop spreading phenomenon is considered.

Influence of Filler Particle Size and Structure on the Recovery of Swollen Polychloroprene RubberUnderCompression Strain

The effect of carbon black particle size and structure on the equilibrium volume swelling and elastic recovery of polychloroprene rubber immersed in hydraulic oil and subjected to uniaxial compression stress was investigated in this study.

Thermodynamics of swelling in unfilled and filler-loaded networks

Within the framework of the van der Waals-network model a consistent interpretation of swelling and simple extension in differently crosslinked networks is presented. It is observed that the excess parameters in the Staverman-Koningsveld-Kleintjens version do not depend on the degree of crosslinking. Swelling of filler-loaded rubbers shows universal features because of not depending on the type and the properties of the filler. By introducing the Einstein-Smallwood modification in an adequate manner one understands this phenomenon without any further parameter adjustments. It is the consequence of having “quasi-permanent” filler-to-matrix contacts that are not modified in presence of solvent molecules. The excess-parameters in the swollen matrix are not affected. The entropy elastic stress due to the swelling induced deformation of the matrix is apparently too small as to enforce chain-slippage. The strength of the adhesion of the polymer inhibits filler-to-solvent contacts. These results defend the mean-field treatment of the boundary problem as presented by Einstein-Smallwood, and allows a valuable proof of the thermodynamics of swelling in networks.

Deuterium NMR of Strained Swollen Crossunked Elastomers: Effect of Crosslink Density on the Orientational Order of Chain Segments

Abstract The 2H NMR of uniaxially strained swollen chloroprene rubbers and butadiene-styrene copolymers with different crosslink densities is studied. the relative number of chain segments between cross-links of various samples is obtained. the results are in approximate agreement with those obtained from the Flory equilibrium-swelling method. It is found that the enhancement factor G depends not only on the lattice-walk model and swelling of rubber, such as Tanaka etc. expected, but also on the crosslink density and the structure of the rubber. the formula relating G to the number of chain segments between cross links is derived from theory. Moreover, we can also estimate the relation between the enhancement factor Gr of real rubber and G calculated from the theory of the lattice model. the 2H NMR results of these samples indicate that the interaction between chain segments decreases with increasing crosslink density.

Modeling high‐pressure gas–polymer mixtures using the sanchez‐lacombe equation of state

AbstractThe Sanchez‐Lacombe equation of state was used to model the sorption of high‐pressure gases into solid, amorphous polymers and molten polymers. Only one adjustable parameter per binary pair, δ12, was used in the mixing rules to correct the deviation of the characteristic pressure of the mixture, P12*, from the geometric mean. The values of δ12 which gave the best fit of the available literature data for the carbon dioxide–polymethyl methacrylate, carbon dioxide–silicone rubber, ethylene–low density polyethylene, methane–polyisobutylene, methane–low‐density and high‐density polyethylene, and methane–polystyrene systems ranged from −0.019 to 0.136. In all cases, the calculated sorption isotherms were in reasonably good agreement with the experimental data. The resultant swelling of polymethyl methacrylate and silicone rubber was also well represented by the Sanchez‐Lacombe equation of state. Because the Sanchez‐Lacombe theory is based on lattice‐fluid theory, the sorption calculations are limited to polymers which are noncrystalline, not cross‐linked or slightly crosslinked, above their glass transition temperature, or above their melting temperature. The sorption data for the amorphous polymers considered in this study were either at temperatures above the glass transition temperature of the polymer or were at sufficiently high pressures that the temperature was above the effective glass transition temperature as predicted from a theoretical relation presented by Chow.

Effect of strain on swelling of elastomers

It was shown that equilibrium swelling of rubber increases during elongation and decreases during compression. Strain in swollen polymers creates a gradient of chemical potential of the solvent in the direction of transfer of the material from an equilibrium swollen polymer to the surrounding medium and vice versa.

Effect of Different Water-Soluble Additives on Water Sorption into Silicone Rubber

□ The ability of ethylene glycol; glycerin; polyethylene glycols 200, 400, and 6000; polysorbate 80; and lactose dispersed in silicone rubber, to promote water sorption into the polymer was investigated in water and in isotonic (pH7.4) phosphate buffer. Polyethylene glycols 200 and 400, lactose, and, especially, glycerin were effective water carriers. Marked differences in the kinetics of rubber swelling were observed, depending on the carrier. The swelling patterns relative to ethylene glycol, glycerin, and polyethylene glycol 200 showed a maximum due to significant leaching of these additives from the polymer. Steady swelling degrees were afforded by polyethylene glycols 400 and 6000 and by polysorbate 80. The interdependent processes of polymer imbibition and carrier release were speeded up without altering their kinetic patterns by increasing the initial surface–volume ratio of the devices. A proportionality resulted between maximal swelling and initial carrier concentration, although the swelling patterns were substantially unaffected by this variable.

Effects of brake fluid components on rubber

In the hydraulic drives of automotive brake systems, rubber seal rings are used to prevent leakage of brake fluid. The hardness and swelling of the seal rubbers, when exposed to brake fluid, must remain within limits such that the seals will give reliable operation. According to certain specifications used in other countries (SAE 1702, SAE 1703, DOT-3, and DOT-4), brake fluid is considered as satisfactory for use with respec~ to the effect on rubber if exposure of an SBR rubber seal ring to the fluid gives an increase in diameter amounting to 0.14-1.40 ram, and if the rubber hardness decreases by no more than 15 arbitrary- units. According to the recommendations of the CMEA specification RS 2621-70 and USSR specifications, the effect of brake fluid on rubber is governed by limits on the changes in volume and hardness of standard specimens (strips) of vulcanized rubber based on either natural rubber or synthetic rubber (NR and SR). Allowable volume change for the vulcanized rubber based on NR are 2-8%, and for the vulcanized rubber based on SR 3-12%, after holding in the brake fluid for 70 h at respective temperatures of 70 ~ and 120~ the allowable decreases in hardness are 10 and 15 arbitrary units, respectively. The test temperature is set on the basis of the heat resistance of the vulcanized rubber seal rings. Brake fluids are multieomponent systems; therefore, in developing new formulations, the effects of the individual components on rubber are of particular interest. Information has been reported in the literature on a number of chemical compounds that might find application as brake fluid components. In [1], effects onSBR rubber (based on SR) were investigated for esters of monocarboxylic and dicarboxylic acids, glycol ethers~ glycerol ethers, and other compounds; also, boiling points, low-temperature- viscosities, and hygroscopieities were determined for these compounds. From the standpoint of compatability with rubber, in the opinion of these investigators, the most suitable materials are complex hydroxy-ethers. We have investigated the volume swelling of samples of USSR rubbers when exposed to various chemical products that have prope~ies potentially suitable for use as brake fluid components. The results obtained in thiswork can be used as a basis for considering the products for two possible uses: as a base component of hydraulic fluids if the rubber swelling is within limits close to the requirements, or as additives to improve certain properties of the formulation if the material itself gives excessive swelling or shrinkage of the rubber. The brake fluids were tested for compatibility with rubber in accordance with the generally accepted procedure. Standard test specimens were cut from vulcanized rubber No. 7-2462 (based on NR) and No. 51-1524 (based on SR), these two rubbers representing materials that are used in manufacturing seal rings for USSR automotive brake systems. The test results* are listed in Table 1. In the polyoxypropylene glycols, as the molecular weight is increased, the rubber swelling drops off, particularly in the case of the NR-based rubber, and the hardness increases. The triols based on glycerol and * V. A. Pozhidaev took part in the tests.

Mechanism of rubber swelling in oils and greases

Mechanism of rubber swelling in oils and greases

Mold-Flow-Induced Anisotropy in Nitrile Rubber

Abstract 1. Data in all the investigated locations showed anisotropic swelling. The anisotropy is believed to be induced by vulcanization of the rubber in a strained state caused by mold flow. 2. Data and theories of composite networks suggest that the swelling of rubber in the strained direction would be less than in other directions. 3. Anisotropic swelling data were consistent with the flow pattern of rubber in the mold. 4. The volumetric swell ratios at different locations varied only slightly, in-dicating that crosslinking was uniform. 5. The shear rate for compression molding is 1–10 s−1, calendering is 10–102 s−1 extrusion is 102–103 s−1, and injection molding is 103–104 s−1. Hence, rubber products processed by other methods are expected to be even more anisotropic. 6. Microswelling is a fast and easy technique to monitor the strain-induced anisotropy and to infer the flow pattern during mold filling. 7. Mechanical data of composite networks formed under different strains should be collected, and theories should be checked, then, mechanical behavior of networks based on microswelling data may be predictable. 8. Engineering design for both end use and molding should take this frozen strain-induced anisotropy into consideration.

Model for the Kinematics of Polymer Dissolution

The dissolution of glassy polymers is described by a phenomenological model of the motion of two boundaries: the liquid-gel boundary and the gel-glass boundary. The motion of these boundaries, as well as the concentration profile in the layers of a dissolving polymer, was obtained by numerical solution of the Stefan boundary value problem. Confirmation of the experimental program written to simulate the problem is established by its good agreement with direct observation of the dissolution dynamics of polystyrene in methyl ethyl ketone. A potential application of this model to the study of the dissolution dynamics of other polymer-solvent systems is done by simulating the dissolution of three types of polymer-solvent pairs: 1) swelling of rubber, 2) high glass transition concentration, and 3) low glass transition concentration. Contrasting dissolution characteristics are shown for the effect of different types of polymer-solvent pairs as well as for the effect of different molecular weights for the same type of polymer-solvent pair.

On Swelling of Natural Rubber in Organic Solvents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOn Swelling of Natural Rubber in Organic SolventsWitold BrostowCite this: Macromolecules 1971, 4, 6, 742–747Publication Date (Print):November 1, 1971Publication History Published online1 May 2002Published inissue 1 November 1971https://doi.org/10.1021/ma60024a014RIGHTS & PERMISSIONSArticle Views345Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (654 KB) Get e-Alerts Get e-Alerts

Unidirectional fiber–polymer composites: Swelling and modulus anisotropy

AbstractThe solvent swelling of unidirectional rubber–fiber composites was studied. The amount of matrix swelling was constrained to the extent that would be predicted from the thermodynamic theories of elasticity and polymer–solvent interaction. The geometry of swelling was found to be orthotropic in nature. A simple trigonometric function was derived to relate linear deformation due to swelling to the angle which the direction of its measurement makes with the fiber direction. The validity of the derivation was demonstrated experimentally. Considering swelling to be the imposition of tensile forces of equal magnitude in all directions, and considering a swelling‐induced linear deformation to be analogous to a tensile compliance, a simple set of relationships between elastic parameters and their direction of measurement was derived: where Eθ, Gθ, vθ, and ηθ are Young's modulus, shear modulus, Poisson's ratio, and the shear coupling ratio measured in a longitudinal transverse plane at an angle with the fiber direction, respectively, and EL, GLT, and θLT are the longitudinal Young's modulus, the longitudinal transverse shear modulus, and the longitudinal transverse Poisson ratio, respectively. Further simplifying the case of combined transverse isotropy and special orthotropy was the conclusion that 1/GLT = 1/ET + (1 + 2vLT)/EL. The relationships for G and E were experimentally demonstrated.

Water absorption and its effect on rubber strength

The effect of the swelling of rubbers in water and their recovery on the tear strength of the material has been investigated and a mechanism of water absorption is proposed. It is shown that there is a fundamental difference between the mechanism of water absorption and swelling in solvents. The strength of a rubber dried after being kept in water is anomalously high. This effect is explained in terms of the proposed polymer-nonsolvent interaction mechanism.

Effect of Network Breakdown and Re-Formation on the Swelling of Rubbers in Compression

Abstract Effect of changes in network structure on equilibrium swelling of a crosslinked rubber subjected to uniaxial compressive stress is calculated on the basis of the ‘two-network’ hypothesis. Equations are also derived for compressive force and amount of elastic recovery after removal of the stress. Numerical examples are given to illustrate effects predicted by the theory for a rubber in a good swelling agent.

The permeability and swelling of elastomers and plastics at high hydrostatic pressures

Resistance to penetration of water is an important requirement for materials used in hydrospace application. In this paper the effects of hydrostatic pressure on the permeability and swelling of elastomers and plastics, and correlations between swelling and permeability are discussed from the theoretical and practical points of view. It is shown that hydrostatic pressure can have various effects on the permeability of polymeric materials to water and other permeants, depending on the exposure conditions and the permeation mechanism. On one hand a decrease in permeability with increasing hydrostatic pressure was observed for butyl rubber exposed to pressurized water on the upstream side and to an environment of low water vapour pressure on the downsteam side. Other materials such as polyethylene, polyurethane and nylon exhibited either a similar decrease or no change in permeability with increasing hydrostatic pressure. On the other hand it is well known that water flow through porous materials, and through non-porous materials used for desalination processes, such as cellulose acetate, increases considerably with increasing hydrostatic pressure. These differences in behaviour, and more complicated correlations, are explained on the basis of thermodynamic considerations. It is also shown that hydrostatic pressure does not increase the swelling of rubbers exposed in the ocean and that there is no simple correlation between swelling and permeability. The reasons for this are discussed. From the practical point of view it follows that: 1. 1. Exposure of hydrophones to great depth will not aggravate those problems which are caused by water permeation through their rubber boots. 2. 2. Materials intended in applications where imperviousness is important cannot be chosen on the basis of swelling tests. 3. 3. In order to predict the extent of water penetration through a barrier material, knowledge of the mechanism of permeation and the exposure conditions is necessary.

Chemistry and Technology of Elastomeric Polysulfide Polymers

Abstract The first synthetic rubber manufactured in the United States was of the polysulfide type. In 1927 Patrick and Mnookin had obtained the first of a series of patents on the products from the reaction of organic dihalides and inorganic polysulfides. Production was started in Kansas City in 1929 with the first of the polysulfide elastomers, the ethylene tetrasulfide polymer, under the trademark name Thiokol A. Thus, the Thiokol Chemical Corporation started its long association with the polysulfide polymers. Interest developed in many countries because of the potential cheapness and availability of the raw materials required. In the case of Thiokol A, these were sulfur, caustic soda, and ethylene dichloride from ethylene and chlorine. The most interesting property of these polymers was the unusual inertness to solvents and hydrocarbon fuels in contrast to the easy swelling of natural rubber. In this respect, Thiokol A was more inert than the polysulfide polymers to follow, but it had also some less desirable properties. It was difficult to process, had a bad odor that remained to some extent even when fully cured, and gave off irritating fumes during processing. It was subsequently found that the polymers from bis (2-chloroethyl) ether were free of this problem, processed better and gave improved physical properties. Thiokol B and Thiokol D were respectively the tetrasulfide and disulfide elastomers derived from bis-2-chloroethyl ether. These resulted from a study of the effect of polymer structure on polymer odor and properties that indicated a reduction in odor when the polysulfide units were separated by an increasing number of atoms. However, the process for making these polymers gave a high byproduct yield of the six atom heterocycle, thioxane, which has a pungent odor and no economic value. Five and six membered monosulfide rings are formed readily with the corresponding 1, 4- and 1, 5-dichloro aliphatic compounds.