not as good and that total strain after break, contact angle and nonvolatile
solids content need to be measured experimentally. This is
shown in the graphs depicting predicted values vs. experimental values
for each property (see Fig. 4).
Equally, these equations are graphed in contour and surface plots in
Fig. 5. From Fig. 5(a), it can be observed the relation between the
factors silicon dioxide (C) and Latex type ratio (D) added to WPCA's
formulation and its viscosity. Silicon dioxide acts as a viscosity
modifier, this component is able to increase up to 80% the viscosity
values [26–28], as can been seen at contour graphic. This viscosity
increase is created by roughly spherical particles with a diameter of
100 nm, these particles form aggregates, which in turn are grouped to
make larger agglomerates, which form a gel-type three-dimensional
structure when a dispersion of them is allowed to stand [29].
Meanwhile, latex type ratio also acts as a viscosity modifier that
increases the viscosity value up to 60%. This rheological behavior
affects characteristics such as: processing capacity, dosage, and wettability,
which are indicators of product performance and, therefore, of
its quality [29]. Viscosity also determines the selection of an appropriate
adhesive for industrial scale [12].
Fig. 5(b) shows the non-volatile solids content of WPCA formulations
as functions of the factors that have most influence on it: Silicon
dioxide (C) and latex type ratio (D). Latex type ratio represents the
adhesive polymer, which is the major component and the skeleton of an
adhesive formulation, and gives the cohesive properties [30]. Silicon
dioxide is not easily volatized but it aids with the adhesion to metallic
substrates. Usually, the non-volatile solids content of a waterborne
adhesive is in the range of 40–50%, while the solids content of a solvent
borne adhesive is in a range of 20–30% [31]. This is why waterborne
adhesives are more efficient than solvent borne adhesives.
Fig. 5(c) shows the wettability of WPCA formulations represented
by the contact angle, as a function of the factors that have the most
significance. Silicon dioxide (C) and latex type ratio (D) are again the
factors that have the major influence. These components tend to
increase the cohesive forces of the adhesive, modifying its surface