For both vegetable oil based and mineral oil based cutting fluids,
water to oil ratio of 9: 1 was used. The new cutting fluid did not
include banned products in their composition like chlorine substances
and nitrosamines. Simpler formula was adopted with fewer
additives to facilitate easy treatment and disposal of cutting fluid
after use as suggested by Hubner (1994). The formulation of oil-inwater
emulsion cutting fluids using palm kernel oil (PKO) and
cottonseed oil (CSO) involved the application of design of experiment
(DOE) method under the conditions established by a 24 full
factorial design. Tables 1 and 2 show variables (additives) and levels
employed in the factorial design and experimental matrix of the 24
full factorial designs respectively.
Each run as shown in Table 2 was formulated by first mixing oil
in water with additives. This mixture was done with the aid of
mechanical stirrer at 760 rpm for 10 min at room temperature of
25 C as shown in Fig. 1.
The data obtained for the pH values for all the experimental runs
were analysed statistically using version 6 of DOE software. The
software used for the analysis uses a second degree polynomial,
approximated by equation (1), to predict the response, Y, which
includes all factors as well as the most effectual way the factors
interact.
Y ¼ b0 þXbixi þXbiix2
i þXbijxixj (1)
whereb0 is constant, bi and bij are coefficient of ij; xi represents
independent variables and xij denotes the interactions thereof
(Montgomery, 2009).
The optimal values were then used to formulate and characterize
the new cutting fluid. The mineral (conventional) oil which
was sourced as concentrated oil was used to prepare emulsion
cutting fluid without any addition of additives.