Composite properties swelling

The main efforts are directed toward better performing, more cost-effective membranes, based on (1) reduction of membrane thickness [66, 67], (2) control of composition and swelling properties via the equivalent weight (or ion-exchange capacity) [67] or via reinforcing the nonconductive matrix by means of... 

Thermal cycling of SiC/RBSN in nitrogen had no effect on mechanical properties, but in oxygen environment, composite properties degraded due to internal oxidation (discussed in Section 1.2d) and swelling as shown in Table 11. 

Reduced water adsorption by the composite, reducing swelling and stabilizing electrical properties. 

Improved composite properties. These can include increased strength and stiffness, better impact strength, increased abrasion resistance, reduced adsorption and less swelling in the presence of water and other fluids. 

Burnside and Giannelis discussed the nanostructure-property relationships in polydimelhylsiloxane/LS nanocomposites. The solvent uptake in this nanostruc-tured silicon rubber was dramatically decreased when compared to conventional composites. Both swelling behavior and modulus were related to the excess amoimt of bonded rubber formed in the nanocomposites compared to conventional composites. 

Properties Involving Utilization. Coal rank is the most important single property for appHcation of coal. Rank sets limits on many properties such as volatile matter, calorific value, and swelling and coking characteristics. Other properties of significance include grindabHity, ash content and composition, and sulfur content. 

Structure—Property Relationships The modem approach to the development of new elastomers is to satisfy specific appHcation requirements. AcryUc elastomers are very powerhil in this respect, because they can be tailor-made to meet certain performance requirements. Even though the stmcture—property studies are proprietary knowledge of each acryUc elastomer manufacturer, some significant information can be found in the Hterature (18,41). Figure 3a shows the predicted according to GCT, and the volume swell in reference duid, ASTM No. 3 oil (42), related to each monomer composition. Figure 3b shows thermal aging resistance of acryHc elastomers as a function of backbone monomer composition. 

Fig. 3. Elastomer properties as a function of monomer composition, butyl acrylate (BA), ethyl acrylate (FA), and methoxyethyl acrylate (MEA). (a), (—) glass-transition temperature (------------) swelling in ASTM No. 3 oil (b) (-) residual elongation at break, %, after heat aging.

In attempts to further improve the stability of fluorine-containing elastomers Du Pont developed a polymer with no C—H groups. This material is a terpolymer of tetrafluoroethylene, perfluoro(methyl vinyl ether) and, in small amounts, a cure site monomer of undisclosed composition. Marketed as Kalrez in 1975 the polymer withstands air oxidation up to 290-315°C and has an extremely low volume swell in a wide range of solvents, properties unmatched by any other commercial fluoroelastomer. This rubber is, however, very expensive, about 20 times the cost of the FKM rubbers and quoted at 1500/kg in 1990, and production is only of the order of 1 t.p.a. In 1992 Du Pont offered a material costing about 75% as much as Kalrez and marketed as Zalak. Structurally, it differs mainly from Kalrez in the choice of cure-site monomer. 

Whilst increasing the length of alkyl side chain can, to some extent, depress Tg and improve low-temperature properties this is at the expense of oil resistance. On the other hand lengthening of the side chain by incorporation of an —O— or an —S— linkage could often depress Tg and reduce swelling in hydrocarbon oils. This led to the commercial development of copolymers of either ethyl or butyl acrylate with an alkoxy acrylate comprising some 20-50% of the total composition. Typical of such alkoxy compounds are methoxyethyl acrylate (1) and ethoxyethyl acrylate (11) ... 

Silicone rubber-hydrogel composite is a two-phase system that is capable of swelling in water. The hydrogels prepared have different chemical compositions, size and shape of particles, and correspondingly different specific surfaces. It was found that the mechanical properties of silicone rubber-hydrogel composites depend mostly on the magnitude of the contact surface of both phases. ... 

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