Rubber swelling

Rubber swelling modifies the liquid/solid work of adhesion. Wo, because in addition to the initial liquid/solid interactions, liquid diffusion into the solid produces supplementary liquid/liquid interactions, hquid molecules having passed through the liquid/solid interface. Therefore, to the initial work of adhesion in the absence of swelling, Wq, an additional term corresponding to a fraction of the cohesion energy of the liquid, 2y, should be added. If / is the time of diffusion, the work of adhesion at /, Wo(t), can then be expressed as... 

Highly cross-linked rubbers swell less in good solvents than do lightly cross-linked rubbers((188,189). For this reason, swelling in solvents is often used to determine quantitatively the degree of cross-linking. However, in... 

Now, if one is to assume that the rubber swells equally in all directions, even in the presence of the filler, the swollen volume in presence of filler is ... 

This model characterizes surface contacts, deals with agglomerates, and explains rubber swelling. It was further developed to characterize reinforcement as a non-Gaussian phenomenon. The model deals with intra-cluster forces and the stress-strain cycle. It is used in the experimental part on uniaxial compression to... 

For most elastomers the ultimate tensile and elongation values were found to be quantitatively related by simple linear equations to the volume fraction of the rubber swelled In mixtures of gasoline and ethanol or MTBE. They were also found to be related to each other by simple logarithmic relatlonshlps. 

As usual, the equilibrium swelling ratio is obtained by setting pj - Pj = 0 and solving for 92. Let us now apply the above formalism to experimental rubber swelling data. 

All normal metallic materials of construction are suitable for handling acetone but Viton rubbers swell and disintegrate on contact with it. 

MPa. For the lithographic blanket, which is typically polyisoprene rubber, swelling is avoided when... 

The physical significance of C, and Cj is not established. The Ci of equation (11-38) is often assumed to be identical with the of equation (11-37), Some authors suggest that the appearance of C2 is due to time elfects. i,e, that the measurements were not carried out under equilibrium conditions. This is partially confirmed by the fact that the value of Cj falls as the rubber swells, i.e., as the segments become more mobile. Depending on the test conditions, Cj either falls as the temperature rises (more rapid establishment of equilibrium), remains constant, or even increases (development of stresses). 

In certain fluids the polyurethanes, like other rubbers, swell but when removed and allowed to dry out they return to their original dimensions. This is not always so with other elastomers or plastics since they may contain plasticizers which can be leached out by the fluid, resulting in permanent shrinkage. The effect of organic materials on polyurethanes is dependent upon the chemical groups present in these materials. 

When rubber swelled in benzene (49), or when paraffin (50 was absorbed by cured rubber and by rubber gum, the positive temperature coefficients of the sorption velocity suggested that in these and other organic solids vapours are sorbed by processes of activated diffusion. The occurrence of activated diffusion has already been established for gas-rubber (52), cellulose, -bakelite and similar systems (Chap. IX). In liquids also, diffusion constants (53) may be expressed by the equation D = although the values of E are usually smaller. 

As shown above, the vulcanized rubber swelling method can be used in two ways ... 

Metal oxides are used in the curing systems of seal compounds. These are soluble in the inorganic acids that are used in the oil exploration industry, and this leads to the rubber swelling considerably. 

The methyl silicone rubbers swell substantially in hydrocarbon oils and solvents. The introduction of cyanoethyl groups is beneficial in improving the resistance to swelling in these materials but the polymers have not achieved technical significance. Of greater importance are the fluorosilicones such as the rubbers containing the structure ... 

Rubbers swell if a solvent penetrates. This isotropic dilatation becomes particularly large if cross-linked polyelectrolytes are swollen by water. The equilibrium state here is controlled by both the osmotic pressure of the mobile counter-ions and the non-linear network properties. 

Uses Roller cleaner, solubilizer for pigment, disperse, and other padded dyestuffe Features Will not cause rubber swelling normally associated with petroleum-based prods. 

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