Tensile properties of EPDM

Table 9 Effect of Ionomer Concentration on the Tensile Properties of Blends of PP-EPDM...

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... 

The tensile properties of the S-SBR/EPDM blends cured with the uncoated and coated sulfur are shown in Fig. 34. It is clear that the compounds with micro-encapsulated sulfur show largely improved tensile strength, elongation at break, and higher moduli. 

Tensile properties of these two EPDM rubbers are fairly representative of what can be obtained using commercial polymers having a 125° C Mooney viscosity near 55. Tensile strengths as high as 2900 psi have... 

Duvdevani(40) have been directed at modification of ionomer properties by employing polar additives to specifically interact or plasticize the ionic interactions. This plasticization process is necessary to achieve the processability of thermoplastic elastomers based on S-EPDM. Crystalline polar plasticizers such as zinc stearate can markedly affect ionic associations in S-EPDM. For example, low levels of metal stearate can enhance the melt flow of S-EPDM at elevated temperatures and yet improve the tensile properties of this ionomer at ambient temperatures. Above its crystalline melting point, ca. 120°C, zinc stearate is effective at solvating the ionic groups, thus lowering the melt viscosity of the ionomer. At ambient temperatures the crystalline additive acts as a reinforcing filler. 

Data on the 100°C tensile properties of a sulfonated EPDM neutralized with various quaternary tetralkyl phosphonium ions are presented in... 

According to Jain et al. (40), the impact strength of PP increased dramatically when the optimum amount of EPDM was blended. The cross-linking of the EPDM reduced the optimum amount of EPDM. Increased interfacial adhesion due to cross-linking leaded to the reduced EPDM particle sizes and a more uniform particle size distribution. Compared with unvulcanized PP/EPDM blend, the tensile properties of TPV were significantly improved (39,40). 

Figure 15.15 Retention of the tensile properties of NR/EPDM blends with thermal aging (a) non-compatibiUzed compatibiUzed with (b) EPDMTA and (c) EPDMSH. (From Reference 61 with permission from Elsevier Ltd.)...

Table 3.4 gives the properties of EPDM/PP TPVs prepared with different cure systems. As shown, there is substantial improvement in tensile properties and tension set over uncured physical blends for all the crosslinked TPVs. 

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. 

Figure 15 (A) Tensile strength versus draw ratio of nylon 46-Vectra B (75 25 wt ratio) and (B) tensile modulus of the blends when 2.7 wt% of SA-g-EPDM was added. Lines are guides for eyes. Closed symbols are mechanical properties of the binary nylon 46-Vectra B blend (75 25 wt ratio) Source Ref. 57.

The effect of ionomer concentration on the mechanical properties of PP-EPDM blends is given Table 9. It is seen that the tensile strength and modulus show a maximum at 5 wt% of both ionomer A and B, thereafter, it decreases at higher ionomer loading. The properties are higher for ternary blends containing ionomer B than these containing ionomer A. On the other hand, addition... 

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