Sulfur-vulcanized EPDM backbone

Figure 6. Engineering stress-strain at ambient conditions of 303-0, 303-50 and of the sulfur vulcanized EPDM backbone. ASTM die C samples were stretched at 20 in./min.

Ethylene-propylene rubber is a synthetic hydrocarbon-based rubber made either from ethylene-propylene diene monomer or ethylene-propylene terpolymer. These monomers are combined in such a manner as to produce an elastomer with a completely saturated backbone and pendant unsaturation for sulfur vulcanization. As a result of this configuration, vulcanizates of EPDM elastomers are extremely resistant to attack by ozone, oxygen, and weather. 

The diene ethylidiene norbomene in Vistalon EPDM allows sulfur vulcanization (see Table 3.12). 12 1,4-Hexadiene and dicyclopentadi-ene (DCPD) are also used as curing agents. 1 The completely satm ated polymer backbone precludes the need for antioxidants which can... 

The diene ethylidiene norbornene in Vistalon EPDM allows sulfur vulcanization (see Table 3.12). 1,4-Hexadiene and dicyclopentadiene (DCPD) are also used as curing agents.The completely saturated polymer backbone precludes the need for antioxidants that can bleed to the surface (bloom) of the finished product and cause staining. Saturation provides inherent ozone and weather resistance, good thermal properties, and a low compression set. Saturation also allows a relatively high-volume addition of low-cost fillers and oils in compounds while retaining a high level of mechanical properties. The ethylene/propylene monomer ratio also affects the properties. 

Ethylene—Propylene Rubber. Ethylene and propjiene copolymerize to produce a wide range of elastomeric and thermoplastic products. Often a third monomer such dicyclopentadiene, hexadiene, or ethylene norbomene is incorporated at 2—12% into the polymer backbone and leads to the designation ethylene—propylene—diene monomer (EPDM) mbber (see Elastomers, synthetic-ethylene-propylene-diene rubber). The third monomer introduces sites of unsaturation that allow vulcanization by conventional sulfur cures. At high levels of third monomer it is possible to achieve cure rates that are equivalent to conventional mbbers such as SBR and PBD. Ethylene—propylene mbber (EPR) requires peroxide vulcanization. 

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