(Haake Rheomix 3000p). The mixing conditions
were set as follows: fill factor ¼ 0.7, initial chamber
temperature ¼ 60 1C, rotor speed ¼ 40 rpm and
mixing time ¼ 9 min. After mixing, the compounds
were sheeted out on a two-roll mill (Labtech
LRM150). Measurement of Mooney viscosity
(ML1+4 @ 125 1C) was carried out according to
ISO 289 using a Mooney viscometer (TechPro
viscTECH+). The cure characteristics, e.g., scorch
time (ts2) and optimum cure time (tc90) including
minimum torque (ML) and maximum torque (MH)
were determined using a moving die rheometer
(TechPro MD+) at 160 1C following ISO 6502. It
was reported earlier that the torque difference
(MHML) is directly proportional to the degree of
crosslinking, therefore it is employed here to
indirectly represent the crosslink density of the
blend vulcanizates [13].
2.3. Testing of rubber vulcanizates
Determination of the crosslink density was
carried out by immersing the test specimens in
toluene for 72 h at room temperature (23 1C). After
immersion, the specimens were blotted with filter
paper prior to the determination of mass change.
The swelling ratio was then calculated. The dynamic
properties, i.e., storage modulus (E0), and damping
factor (tan d), were investigated using a dynamic
mechanical analyzer (DMA, Gabo Eplexor 25N).
The test was carried out under tension mode at a
frequency of 10 Hz. The test temperature was varied
from 90 to 25 1C. The tensile properties and tear
strength were determined using a universal testing
machine (Instron 5539 series) following ISO 37 and
34, respectively. The hardness was measured using a
Wallace Shore A durometer according to ISO 7619
Part 1. The rebound resilience was determined using