2.3. Testing procedures
2.3.1. Curing characteristics
Curing characteristics of only m-EPM rubber (without any PP) containing cross-linking agents,
DCP/TAC were carried out by using Monsanto Rheometer R100S (an oscillating disc rheometer, ODR) at
180°C for 30 minutes.
2.3.2. Mechanical properties
Tensile tests were carried out according to ASTM D412-98 on dumb-bell shaped specimens using a
universal tensile testing machine Hounsfield H10KS at a constant cross-head speed of 500
mm/min.
Hardness of the samples was measured by a Durometer (Shore A type) as per ASTM D 2240.
Tension set was measured in universal tensile test- ing machine Hounsfield H10KS. The test was car-
ried out at room temperature after stretching the TPV samples for 10 minutes at 100% elongation
according to ASTM D 412-98.
2.3.3. Cross-link density
The overall cross-link density of the TPV samples was determined on the basis of equilibrium
solvent- swelling measurements (in cyclohexane at 23– 25°C) by application of the well-known
modified Flory-Rehner equation for tetrafunctional net- works. A 2 mm thick sample was submerged in
cyclohexane. After 24 hours, the cyclohexane was refreshed. After another 24 hours, the swollen
sam- ple was weighed, dried and weighed again. From the degree of swelling, the crosslink density
(■) was calculated by modified Flory-Rehner equation (1):
■ = -
1 · ln(1 - Vr )+ Vr + Vr
mol/ml
(1)
Vs V 1/ 3 - 0.5·V
r r
where Vs – molar volume of cyclohexane, – poly- mer-swelling solvent interaction parameter or
Flory-Huggins parameter, which in this cases is 0.3 and Vr is the volume fraction of rubber in the
swollen network, Vr is expressed as Vr = 1/(Ar+1) where, Ar is the ratio of the volume of absorbed
cyclohexane to that of rubber after swelling.