Sulfonated-EPDM rubber

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. 

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

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,... 

Property Natural Rubber Butyl Rubber EPDM rubber Chloroprene rubber Nitrile rubber Silicone rubber Chloro sulfon ated polyethylene rubber... 

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. 

The sulfonation of EPDM as shown in Reaction 41b has recently been announced to be under commercial development by Uniroyal (78). Sulfonated EPDM can be classified as an ionic thermoplastic elastomer, whereby ionic interactions between chains act as thermally reversible cross-links. Above certain temperatures these ionic interactions break down, and plastic flow can occur. Upon cooling, these ionic cross-links reform to give the desired property characteristics. To enhance the processability of sulfonated EPDM an ionic plasticizer "ionolyzer" (i.e., zinc stearate) is added to about 20 phr (parts per 100 rubber). Care must be taken to ensure complete neutralization, because it was observed that residual acid can result in covalent cross-linking during fabrication. 

Elastomeric ionomers have also been developed from ethylene-propylene-diene ternary copolymers known as EPDM rubbers. The diene is commonly ethylidene norbomene. Du Pont made carboxylated ionomers by free-radical grafting of maleic anhydride (0.5—5%) onto the diene moiety of the polymer and neutralized the product with rosin salt. The ethylidene norbomene can also be sulfonated, thus ... 

Preparative techniques Sulfonation of rubber Neutralization of sulfo-EPDM Comonomer... 

Ternary blends of nitrile rubber, EPDM rubber and polyaniline doped with dodecylbenzene sulfonic acid were prepared and tested as a microwave absorbing coating (for radar-absorbing systems for stealth defense systems) [64]. Good absorption was noted between 11 and 12 GHz with the ability to improve lower frequency absorption with increased thickness. Crosslinking... 

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

Typically, such behavior was demonstrated in sulfonation products of a synthetic rubber, (EPDM, or VISTALON 2504 an ethylene-propylene-norbornene terpolymer produced by EXXON). 

Polyisobutylene (Butyl Rubber, Copolymer with 0.5-2% Isoprene) (HR) Chloro-Sulfonated Polyethylene (CSM) Ethylene-Propylene Random Copolymer, 50% Ethylene (EPM) Ethylene-Propylene Random Terpolymer 50% Ethylene (EPDM) Poly(Ethyl Acrylate), Usually a Copolymer (ACM) Vinylidene-Fluoride-Chlorotrifluoro Ethylene Random Copolymer (FKM) Vinylidene— Fluoride— Hexafluoropropylene Random Copolymer (FKM)... 

This and LDPE were immiscible [103 105], forming thermoplastic elastomers with two continuous phases or IPNs. These were improved by adding compatibilizers such as epoxidized NR-I-maleated LDPE or sulfonated ethylene propylene-diene rubber (EPDM)-b maleated LDPE. These increased tensile strength, elongation, and adhesive peel strength. 

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