Swelling elastomer

Equipment for storing and handling methanol may be made of carbon or stainless steel. Methanol is aggressive toward copper, zinc, magnesium, tin, lead, and alurninum, which should therefore be avoided. Gasket materials must also be chosen carefiiUy, because some elastomers swell and deteriorate when exposed to methanol. Similarly, the use of plastics for storage is not recommended. 

The Index of refraction was measured at 15°C using Abbe-3L Bausch and Lomb refractomer and a Haake FK constant temperature bath. Refractive Index was first measured for ethanol, Indolene HO-III, and mixtures of both components of known concentrations. From this data calibration curves were obtained to relate component concentration with refractive Index. These calibration curves were used to determine whether or not preferential absorption of one component of the mixture takes place during elastomer swelling due to permeability considerations, or after equilibrium swell Is established due to solubility considerations. 

Qualitatively MTBE Is estimated to have an overall solubility parameter value close to that of Indolene, but has higher polar and hydrogen bonding forces. As a result polar polymers such aa fluorocarbon, epichlorohydrin homopolymer and chlorosulfonated polyethylene tend to swell to a greater extent In MTBE rich mixtures, while nonpolar EPDM elastomer swells to a lesser extent In these mixtures. The very large swell of the fluorocarbon In MTBE Is not surprising since other ethers such as diethyl ether and dioxane are known to swell the fluorocarbon to a large extent [3]. 

Logarithmic correlations of O j versus v and E versus v were also examined as seen In Figure 11 for polyurethane and EPDM elastomers swelled In ethanol and MTBE and In Tables IX and X for all the polymers. Again, the data demonstrate perfect linear relationships. 

In common with the mineral-based H-515 fluid the PAO-based fluids also contain hindered phenol-based anti-oxidants and TCP as an anti-wear agent but, as previously stated, they do not need the addition of a VI improver [27]. PAOs tend to give very low swell of the elastomer types used in the applicable hydraulic systems. A certain degree of elastomer swell is required to ensure good sealing of the system and therefore the PAO-based fluids contain up to 35% by weight of di-ester to produce sufficient seal swell. 

Let us agree that s = 0 corresponds to a constant diffusion coefficient k(u,l) = 1). The analysis of this problem allows us to qualitatively explain many mechanisms of diffusion kinetics of elastomer swelling. 

The above expressions allow us to describe the shape of kinetic curves gi(t) in general terms. In particular, as it follows fromEqs. [6.1.39] - [6.1.41] atq< 1, the kinetic curves in the coordinates (t,gi) are upward convex and have the shape typical for pseudo-normal sorption. This takes place at slinear mode of liquid absorption. At s>Se/2-l the lower part of the kinetic curve is convex in a downward direction and the whole curve becomes S-shaped. Note that in terms of coordinates (t ,gi) at s > 0 all the kinetic curves are S-shaped. Hence, the obtained solutions enable one to describe different anomalies of sorption kinetics observed in the experiments on elastomer swelling in low-molecular liquids. 

Note that all these relations are valid only for sufficiently high values of elastomer swelling ratio. 

Table 6.1.1. Experimental characteristics of elastomer swelling kinetics ...

Figure 6.1.4. Kinetic (a) and strain (b) curves of elastomer swelling in toluene 1 - PBU-3 2 - PBU-4 3 - PBU-1 4 -PBU-2. [Adapted, by permission, from E. Ya. Denisyuk, V. V. Tereshatov, Vysokomol. soed., A42, 74 (2000)].

TABLE 9.7 PMTFPS Elastomer Swelling by Various Fluids... 

Fig. 8. Effect of alcohol I gasoline blends on elastomers swelling in 42% aromatic fuel at 21°C for 20 days.

Fig. 9. Effect of alcohol on elastomer swelling in pure alcohols at 21°C for 20 days. Divisions represent swell in ethyl and propyl alcohols. Where only one division is shown, swell in ethyl and propyl alcohols was very similar.

Figure 6.1.4. Kinetic (a) and strain (b) curves of elastomer swelling in toluene 1 - PBU-3 2 - PBU-4 ...

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