reason for higher gloss of films of ALK 9, which is in agreement with
glossometer values, mentioned in Table 4. The increase in smoothness
is due to better flow and leveling arising out of lower dilution
viscosity of the polymers with increased DPE content (Fig. 1) and
also the controlled initial drying phenomenon as observed from
the DSC study (Fig. 6). Refractive index (RI) of polymers is another
parameter that influences the gloss of coatings [26,27].When measured,
ALK 9 showed a higher RI value (1.494) as compared to ALK 1
(1.481). This observation also supports the higher gloss of the ALK
9 film.
3.6. Chemical resistance and durability
Table 4 illustrates the chemical resistance properties of clear
films. Solvent and acid resistance of all the filmswas good.However,
the alkali resistance of ALK 1 and ALK 2 was inferior as compared
to the rest of the films.
The gloss values of coating films are given in Table 4. Clear differences
were observed in the tested panels. Coatings based on
increased amount of DPE content not only gave the initial higher
gloss but also exhibited best retention values when exposed in
QUVB (max = 313 nm) chamber for 300 and 500 h, respectively.