A statistically designed Analysis of Variance (ANOVA) model
was built in order to obtain a general understanding of the impact
of changing various parameters and their inter-relationships on
the static adhesion between natural rubber and brass-coated steel
cords. The dependent variable is the pull-out force and the three
independent variables are the promoter type, promoter concen-tration and cord type. This ANOVA model is called ‘‘three-way
ANOVA’’. The model was built up using the mix formulations in
Table 2as a center point and varying the promoter type levels
(manobond and KMR), promoter concentration levels (0, 0.5, 1.0,
1.5 and 2.0 phr) and the cord type levels (cord 1 and cord 2).