Volumen II - SAM

Consequently, with the object of establishing the best formulations taking into account all tests performed in
this study, the average value corresponding to coatings prepared with PVC 55% and pigmentation 8, for each
micaceous iron oxide dispersion time considered, was calculated starting from results displayed in Table 4
and applying the above quoted considerations. Thus, the coating C-VIII-3 (average value 8.88) showed the
best efficiency, followed by C-VIII-2 and C-VIII-1 in this order (8.00 and 6.12, respectively).
4. CONCLUSIONS
Micaceous iron oxide. This mineral adequately processed presents lamellar particles; when a coating based
on this pigment is applied, the particles are arranged in parallel to the surface and slightly overlapped. This
multiple layers system acts as an effective barrier since, in correctly formulated and elaborated coatings, the
film permeability allows the requirements of rusting and blistering resistance to be made compatible.
This pigment is neither toxic nor inflammable; this last property could contribute for attaining the selfextinguishing
qualification in those coatings containing this pigment in their composition. Furthermore, it
presents low oil absorption and then products with high content of this pigment can be formulated.
Flame retardant pigments. Zinc borates and trihydrated alumina are good choices for replacing with
efficiency, at least partially, the antimony trioxide in fire retardant coatings. The best results, in the tests
developed for evaluating the performance of coatings against fire, were obtained by employing a mixture of
the three flame retardant pigments mentioned. The well-known synergistic action of antimony trioxide in
presence of chlorinated resins and the behavior of zinc borate and trihydrated alumina determined in thermal
analysis are enough reasons to explain the excellent efficiency observed in the LOI and TFT tests.
Pigment Volume Concentration. Test results pointed out the strong influence of this variable. As
mentioned, the highest PVC but inferior to the correspondent CPVC led to a satisfactory reply in all tests.
From the point of view of the best performance against fire, the highest percentage content of inorganic
components bases the mentioned behavior.
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