Studies on the use of nano zinc oxide and modified silica in NR, CR ...

Chapter 5
93
Ingredient
phr
Table 5.1 Formulations of gum and filled CR compounds
C -1 C - 2 C - 3 C-4 C - 5 C - 6 C- 7 C-8 C - 9 C-10
Neoprene-W 100 100 100 100 100 100 100 100 100 100
Light MgO 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
Stearic acid 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
HS 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
HAF - - - - 40 40 40 40 40 40
DOP - - - - 8 8 8 8 8 8
ZnO(c) 5 - - 2 5 - - 2 - -
ZnO(p) - 2 - - - 2 - - 1 -
ZnO(s) - - 2 - - - 2 - - 1
Na 22 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Mixing was done in a laboratory size (16 X 33 cm) two roll mill at a
friction ratio of 1:1.25 as per ASTM D 3182 (1982).
Testing
The cure characteristics of the mixes were determined using Rubber
Process Analyzer RPA 2000, as per ASTM standard, D 2084–01. Subsequently,
the rubber compounds were vulcanized up to their optimum cure time at
150°C in an electrically heated hydraulic press. The mouldings were cooled
quickly in water at the end of the curing cycle and stored in a cool dark place
for 24 hrs, prior to physical testing.
Physical properties, such as modulus, tensile strength, elongation at
break, tear strength, hardness, heat build–up, compression set, abrasion loss,
flex resistance and ageing resistance were studied as per the respective ASTM
standards. Swelling studies of the compounds were carried out in methyl
ethyl ketone and crosslink densities were calculated.