EPDM, sulfonated

In all the compositions, the DCP-cured blends showed better properties than the corresponding unvulcanized samples. Choudhary et al. [30] further demonstrated the use of EPDM, chlorinated PE, chlorosulfo-nated PE, maleic anhydride modified polyethylene, and blends of epoxidized natural rubber-sulfonated EPDM as compatibilizers in NR-LDPE (low-density PE) blends. 

Xie H. and Ma B., Properties of sulfonated EPDM ionomers obtained by sulfonation in the presence of phase transfer catalyst, J. Macromol. Sci. Phys., 51, 1328, 1989. 

Upaeglis A. and O Shea F.X., Thermoplastic elastomer compounds from sulfonated EPDM ionomers. Rubber Chem. TechnoL, 61, 223, 1988. 

Sulfonated EPDMs are formulated to form a number of rubbery products including adhesives for footwear, garden hoses, and in the formation of calendered sheets. Perfluori-nated ionomers marketed as Nation (DuPont) are used for membrane applications including chemical-processing separations, spent-acid regeneration, electrochemical fuel cells, ion-selective separations, electrodialysis, and in the production of chlorine. It is also employed as a solid -state catalyst in chemical synthesis and processing. lonomers are also used in blends with other polymers. 

Sulfonated ionomers are also characterised by IR spectroscopy [75-77]. Agarwal and coworkers [76] analysed the Zn+2 salt of sulfonated EPDM. The peak at about 1200 cm 1 is due to the asymmetric stretching of the sulfonate group. The band at 1020 cm 1 is ascribed to the symmetric stretching of the -S03 group. The position and nature of the absorption band depend on the nature of the cation [76]. The band at 610-615 cm 1 is due to C-S stretching of the polymer -S03 band. 

Fig. 9 Potential hydrogen bonding in PDMS-g-polyacrylamide/sulfonated-EPDM...

Methods of filler pretreatment silane treated talc increases modulus and reduces compression set maleated or sulfonated EPDM interacts with zinc oxide esterification of precipitated silica with methanol, propanol, and hexadecanol modification of precipitated silica with methacrylic and vinyl silane calcium carbonate was modified with monoallyl and monodecyl maleate ... 

Figure 7. D>Tiamic moduli at 1 Hz as a function of temperature for zinc sulfonated EPDM unplasticized (dottcxi line, G only) and plasticized with zinc stearate (adapted from ref. 20).

Reference 7 reviews a number of electron microscopy studies of ionomer morphology in the period up to 1979. None of these studies makes a convincing case for the direct imaging of ionic clusters. This is because of the small size of the clusters (less than 5 nm based on scattering studies) and difficulties encountered in sample preparation. The entire problem was reexamined in 1980(21). In this study ionomers based on ethylene-methacrylic acid copolymers, sulfonated polypentenamer, sulfonated polystyrene and sulfonated ethylene-propylene-diene rubber (EPDM) were examined. The transfer theory of imaging was used to interpret the results. Solvent casting was found to produce no useful information about ionic clusters, and microtomed sections showed no distinct domain structure even in ionomers neutralized with cesium. Microtomed sections of sulfonated EPDM, however,... 

The second route to ionomers Involves modification of a preformed polymer. Sulfonation of EPDM, for example, permits the preparation of sulfonated-EPDM with a level of sulfonate groups in proportion to the amount of sulfonating agent(27). These reactions are conducted in homogeneous solutions permitting the direct neutralization of the acid functionality to the desired level. Isolation of the neutralized ionomer is effected by conventional polymer isolation techniques, such as coagulation in a nonsolvent or solvent flashing. These procedures are detailed in several patents and publications(28-31). 

A thermopolastic elastomer based on sulfonated-EPDM, S-EPDM, was developed in the 1970 s by Exxon and more recently by Uniroyal. Unlike the synthesis of the carboxylate ionomers described above, S-EPDM is prepared by a post-polymerization sulfonatlon reaction(28). Compared to the metal neutralized S-EPDM, the sulfonic acid derivative is not highly associated. The free acid materials possess low strengths and are less thermally stable. The metal salts of S-EPDM have properties comparable to crosslInked elastomers, but they do exhibit viscous flow at elevated temperatures. In the absence of a polar cosolvent, such as methanol, hydrocarbon solutions of the metal salts of S-EPDM are solid gels at polymer concentrations above several percent(31). With the addition of 1 to 5% alcohol the polymer solution becomes fluid with solution viscosities of the order of 10 to 100 poise. 

Wagener, K. B. Duvdevani, I. "Crystallization and Orientation of Zinc Stearate in Sulfonated EPDM" presented at the ACS meeting, Houston, March 1980 (unpublished). 

Neutralization of Sulfonated EPDM. Neutralization of the polymeric sulfonic acid was accomplished in two ways ... 

After 30 min of agitation and the addition of the antioxidant, the neutralized sulfonated EPDM was isolated by solvent flashing in boiling water. The wet crumb was dried either on a rubber mill at about 220°F or in a laboratory Aeromatic fluid bed dryer at 100°C. 

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