Swelling Performance

Study of the antimicrobial performance of silver-containing nanofibrous webs necessitates their contact with water. The water-swelling performance of nanofibrous 

Reproduced with permission from J. Wu, S. Hou, D. Ren and P.T. Mathei Biomacromolecules, 2009, 10, 2686. 2009, American Chemical Society [49]  

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The repeating unit of PVDF is -CH2-CF2-, and it is a crystalline polymer. For example, X-ray diffraction shows that the crystallinity of Kynar 741 is 60%. The thermal and mechanical properties, solubility, and electrochemical performance of the resin differ with the degree of crystallinity. When the crystallinity is low, the solubility and the swelling performance are high. In the case of the P(VDF-HFP) copolymer, the crystallinity and the melting point decrease with the amount of HFP, and the flexibility of the product also increases. 

The swelling performance of a Kynar product in some carbonates is shown in Figure 11.23. Compared with common polyolefins that do not swell, its swelling rate is very high. Therefore, the PVDF resin will obviously have an effect on the performance of the assembled lithium-ion battery especially, its... 

Swelling performance of a PVDF resin in some solvents at 60°C. 

It is of interest to note that experimental values of the parameter d characterizing the strain dependence of equilibrium swelling ratio for elastomers subjected to uniform biaxial extension closely approximate the theoretical values. It will be recalled that this parameter is specified by Eq. [6.1.21], Moreover, the Floiy theory defines it as d = 2/9 = 0.22(2), whereas the des Cloizeaux law provides d 0.205, which suggests that the proposed model of elastomer swelling performs fairly well. 

Gels. Fluorosihcone fluids with vinyl functionahty can be cured using the platinum catalyst addition reactions. The cure can be controlled such that a gel or a soft, clear, jelly-like form is achieved. Gels with low (12% after 7 d) swell in gasoline fuel are useflil (9) to protect electronics or circuitry from dust, dirt, fuels, and solvents in both hot (up to 150°C) and cold (down to —65° C) environments. Apphcations include automotive, aerospace, and electronic industries, where harsh fuel—solvent conditions exist while performance requirements remain high. 

Alkylamines and diamines are generally classified as corrosive to the skin based on results from laboratory animal (rabbit) studies performed in accordance with the Department of Transportation (DOT) test method (84) rabbits are considered to be especially sensitive to alkylamines which even at low concentrations can induce skin redness and swelling. Oleylamine has been shown to induce mild to moderate skin irritation in laboratory rats when appHed at a concentration of 0.3% in mineral oil (Chemical Manufacturer s Association, 1985). Fatty amines which contain alkyl chains of 10—14 carbons are considered more irritating than related products which contain alkyl chains of 14—18 carbon atoms. Ethoxylation generally decreases the irritation potential of alkylamines. 

The sulfonated resin is a close analogue of -toluenesulfonic acid in terms of stmcture and catalyst performance. In the presence of excess water, the SO H groups are dissociated, and specific acid catalysis takes place in the swelled resin just as it takes place in an aqueous solution. When the catalyst is used with weakly polar reactants or with concentrations of polar reactants that are too low to cause dissociation of the acid groups, general acid catalysis prevails and water is a strong reaction inhibitor (63). 

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. 

Both the dipolymers and terpolymers have excellent resistance to hydrocarbons found m petroleum-based fuels and lubricants The 69 5% F terpolymer resists swellmg m blended fuels that contain metlianol and can be used in contact with certain phosphate ester-based hydraulic fluids Terpolymers are preferred for contact with aromatic solvents, although either type performs well in higher alcohols VDF-based elastomers dissolve m polar aprotic solvents such as ketones, esters, amides, and certam ethers These elastomers are therefore not suitable for contact with fluids that contain substantial amounts of these solvents because of excessive swell and consequent loss of mechanical properties... 

The solvent in which the polymer network swelled is able to change the number of intermolecular bonds, to decrease observable flexibility of chain parts between points, and to stretch the system, i.e., to perform labor over it. Its influence on the Qon parameter, according to accepted approximations, is similar to the influence on the process in which only low-molecular compounds participate. Some deviation can be observed as a consequence of suppressing the solvent molecules in the network. One can find that the change of observable local rigidity of the chain as a consequence of network swelling is similar by its first approximation to its change for... 

Check for box swell and/or pin stretch. These are indications of over-torquing, and their presence gready affects the future performance of the Joint. 

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