The Hansen solubility parameters were determined for three hydrocarbon fluids, equivalent to naphthenic mineral oil of different degrees of refinement. This was done by an indirect method based on the solubility of the hydrocarbon fluids in a system of solvents with known Hansen solubility parameters. It was concluded that the method may serve as a tool to estimate the approximate solubility parameters of naphthenic oil. However, in this study, the accuracy was insufficient to separate naphthenic oil of different degrees of refinement.

Determination of Three-Dimensional Solubility Parameters and Solubility Spheres for Naphthenic Mineral Oils

Autohesion is discussed emphasising in particular the influence of polymer chain structure on apparent rates of diffusion. The full range of autohesive levels which exists amongst rubbery polymers is rationalised by proposing a distinction between inter-chain free volume and “intra-chain” free volume, the latter being a collation of free volume regions “contained” in cavities associated with permanent polymer chain structural features which especially apply for certain polymer types. The coincidence of several such cavities plus the intervening inter-chain space causes the formation of holes which may attain sufficient size during normal chain thermal fluctuations to facilitate forward motion of an incoming chain. The concept of free volume has been used to demonstrate the proposed model semi-quantitatively. Comparison with a simple model, involving inter-chain free volume only, is made throughout the calculation. The proposed model, in showing general agreement for several elastomers between fre...

The Influence of Structure on Autohesion (Self-Tack) and other forms of Diffusion into Polymers

Relation between activation energy and induction in rubber sulfur vulcanization: An experimental study

A unified approach to transport phenomena in polymeric media—II Diffusion in solid structured polymers

Publisher Summary
This chapter discusses various aspects of elastomer blends. Blending or mixing of elastomers is undertaken for three main reasons: improvement of the technical properties of the original elastomer, achievement of better processing behavior, and lowering of compound cost. All elastomers have deficiencies in one or more properties and blending is a way of obtaining optimum all-round performance. Elastomer blends are one class of composite materials used in polymer-based industrial products. They are macro scale mixes of high molecular weight elastomer phases. On a microstructural scale, the elastomer could contain blocky or crystalline chain segments which act as reinforcing agents or stiffeners. These may be similar to the repeating units of the elastomeric part.

12 – Elastomer Blends

Migration of oils, curatives, antioxidants, and other compounding materials in a vulcanized rubber matrix is a general phenomenon. A continuing, long range program has been undertaken in these laboratories to understand better this effect, in order that ultimately the compounder can predict, from a knowledge of the molecular nature of the penetrant and the physico-chemical properties of the cured matrix, the distribution of the various components during the service life of the finished rubber product. A sensitive radiotracer approach with earbon—14 is being used to study this system. Earlier work in this program has established the general value of the diffusion coefficient for whole paraffinic oils and for aromatic oils and their fractions. In general, this has shown that moderate variations in the molecular composition of the aromatic portions of the oils have only minor effects on these migration rates. Using similar computer derived diffusion coefficients, the current data indicate that napht...

The Migration of Extender Oil in Natural and Synthetic Rubber. IV. Effect of Saturates Geometry and Carbon Black Type on Diffusion Rates

Using carbon-14 labelled aromatic extender oil as a penetrant species, diffusion rates were measured in practical elastomeric compounds of high oil concentration, and in elastomer compounds based on blended polymers. These results, combined with earlier data, allow the calculation of the locus of oil during the service life of the rubber product. Increasing the concentration of oil increases the rate of diffusion of oil. Butyl rubber was the most sensitive to this effect, albeit the slowest in rate of migration, with a 2-fold increase in migration rate over the range of oil concentration of 2–27%, followed by polybutadiene, 1.53; natural rubber, 1.27; and ethylene-propylene-diene rubber, 1.26, and SBR, 1.00. Polymer blends display no synergism in their effect on diffusion; the diffusivity of oil in the blends was predicted exactly by the weighted average of polymer composition. Further studies of the effect of dynamic flexing indicated that, at constant temperature, static and dynamic conditions ...

The Migration of Extender Oil in Natural and Synthetic Rubber. V. Dependence of Diffusion Rates on Oil Concentration and Elastomer Blend Ratios. The Locus of Oil in a Simulated Tire during Service

Previous work in diffusion of whole extender oil and extender oil fractions in practical rubber compounds has shown the nature of the rubber matrix to be the major controlling factor. Therefore, a sensitive diffusivity approach, using radiotracer labeled hydrocarbon penetrants of sizes comparable to the size of a rotating segment, was used to study various aspects of the matrix structure on penetrant diffusion for polybutadiene, styrene—butadiene, and Butyl rubbers. These results were compared with fractional free volume measurements made by a thermal expansion technique. Neither fractional free volume nor diffusivity of phenyldodecane, benz-a-anthracene, or n-octadecane was affected by 5-fold variations of crosslink density or by variations in loading of 10 to 80 parts of carbon black (HAF-LS); nor were they affected by changes from FEF to SAF black at a 50 phr level. Glass transition temperature and fractional free volume are both affected by increasing percentages of benzene or phenyldodecane,...

The Migration of Extender Oil in Natural and Synthetic Rubber. VI. The Use of Oil Type Molecules as Penetrants to Elucidate Elastomeric Molecular Structure

B. G. Corman

Papers

The Migration of Extender Oil in Natural and Synthetic Rubber. IV. Effect of Saturates Geometry and Carbon Black Type on Diffusion Rates

The Migration of Extender Oil in Natural and Synthetic Rubber. V. Dependence of Diffusion Rates on Oil Concentration and Elastomer Blend Ratios. The Locus of Oil in a Simulated Tire during Service

The Migration of Extender Oil in Natural and Synthetic Rubber. VI. The Use of Oil Type Molecules as Penetrants to Elucidate Elastomeric Molecular Structure