Ethylene-propylene-diene tensile properties

Structural Factors and Tensile Properties of Ethylene-Propylene—Diene Terpolymers Prepared with Various Catalyst Systems... 

Ethylene-propylene-diene terpolymers (EPDM), with their inherent complexity in structural parameters, owe their tensile properties to specific structures dictated by polymerization conditions, among which the controlling factor is the catalyst used in preparing the polymers. However, no detailed studies on correlation between tensile properties and EPDM structures have been published (l,2). An unusual vulcanization behavior of EPDMs prepared with vanadium carboxylates (typified by Vr g, carboxylate of mixed acids of Ccj-Cq) has been recently reported Q). This EPDM attains target tensile properties in 18 and 12 minutes at vulcanization temperatures of 150 and l60°C respectively, while for EPDMs prepared with V0Cl -Et3Al2Cl or V(acac) -Et2AlCl, about 50 and 0 minutes are usually required at the respective vulcanization temperatures, all with dieyclopentadiene (DCPD) as the third monomer and with the same vulcanization recipe. This observation prompted us to inquire into the inherent structural factors... 

Recently there has been considerable work on metal-neutralized sulfonated elastomers (23,24,25). The effect of various monovalent and divalent cations on physical properties of sulfonated ethylene-propylene-diene monomers (EPDM s) has been investigated and large differences have been found in both melt-flow rates and tensile properties, depending on the cation used. 

A blend of low-density polyethylene (LDPE) polyethylene (LDPE) with the terpolymer ethylene-propylene-diene monomer rubber (EPDM) exhibits a synergistic effect on tensile strength if EPDM is partially crystalline, but a nonsynergistic effect if the EPDM is amorphous [65]. This example shows the dramatic effect that morphology can have on properties of polymer blends. The synergism apparently arises from a tendency for crystallites in the LDPE to nucleate crystalli2ation of ethylene segments in the EPDM. 

Common examples of miscible blends are ethylene-propylene copolymers of different composition that result in an elastomer comprising a semicrystalline, higher ethylene content and an amorphous, lower ethylene content components. These blends combine the higher tensile strength of the semicrystaUine polymers and the favorable low temperature properties of amorphous polymers. Chemical differences in miscible blends of ethylene-propylene and styrene-butadiene copolymers can also arise from differences in the distribution and the type of vulcanization site on the elastomer. The uneven distribution of diene, which is the site for vulcanization in blends of ethylene-propylene-diene elastomers, can lead to the formation of two distinct, intermingled vulcanization networks. 

Base rubbers may be based on silicone, fluoropolymers, or hydrocarbons. Although silicone rubbers such as silicone S and G have been applied in stacks, it has become clear that they are not sufficiently stable [83-85]. Materials like ethylene-propylene-diene-monomer (EPDM), butyl rubber (IRR), or fluororubbers (FKM such as Viton )seem better suited. Further research is carried out to optimize properties like hardness, tensile strength, and stress relaxation. Also the morphology is being considered, with apparently a preference for profiled over flat gaskets. 

Maleinized polybutadiene has demonstrated particularly favourable effects for filled elastomers, improving the tensile strength, tear strength and modulus of a sulphur cured EPDM (ethylene propylene diene monomer rubber) containing 100 phr filler, while a stearic acid coating actually caused all these properties to deteriorate significantly. 

Ismail, H., Pasbakhsh, P., Fauzi, M.N.A., Abu Bakar, A., 2008. Morphological, thermal and tensile properties of haUoysite nanotuhes fiUed ethylene propylene diene monomer (EPDM) nanocomposites. Polymer Testing 27, 841—850. 

SBR elastomer with known crosslinking densities was studied in dynamic shear and tensile creep and data collected from -30 to 70 °C used to construct TTS master curves. In addition to a temperature shift factor a vertical shift factor was required from 10 to 30 °C to account for changes in density. Linear viscoelastic properties were observed in accordance with the classical theory of rubber elasticity. Standard vertical shift factors were required in a comparative TTS test with uncrosslinked polybutadiene and poly(ethylene-cu-propylene-co-diene monomer) (EPDM). ... 

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