Page 53 - Handbook of Surface Improvement and Modification

48 Gloss Enhancement

3.3 METHODS AND MECHANISMS OF GLOSS ENHANCEMENT

The overprint coatings can be formulated to provide different degrees of gloss, varying
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from matte to high gloss. A glossy surface requires a uniform coating and a smooth film
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surface.
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The type of amine hardener in epoxy coating affected gloss of unfilled coatings. A
high gloss (i.e., >100 gloss units) was obtained when isophorone diamine, phenalkyl
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amine, and tetraethylene pentamine were used. Gloss correlated with surface roughness. 9
When carbon nanotubes were added they protruded from coatings and increased surface
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roughness contributing to a decreased gloss. The gloss of unfilled coatings depended on
reactivity with carbon dioxide from air (creation of ammonium carbonate/carbamate
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results in blushing/blooming of an epoxy coating surface).
Highly branched chains have several advantages compared to the conventional alkyd
resins with the same molecular weight, such as lower viscosity, higher gloss, better chem-
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ical resistance, and shorter drying time. This was confirmed in the case of hyper-
branched alkyd resins which were synthesized by reacting the hydroxyl end-groups of
hyperbranched polyesters, based on 1,3,5-tris(2-hydroxyethyl) cyanuric acid as a tri-func-
tional core, with different oil fatty acids, namely, linseed, soya and sunflower oil fatty
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acids.
Superhydrophobic metal coatings do not retain the original metallic luster. A super-
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hydrophobic and high-gloss copper coating can be produced on aluminum substrate. The
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wettability and gloss were tuned by the concentration of the precursor. When the CuSO 4
concentration was 30 mmol/L, the coating exhibited a sub-micro/nano binary structure, in
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which 20–30 nm protuberances were grown on 300–500 nm mastoids. This morphology
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resulted with superhydrophobic and high-glossy properties.
Pigment coating is widely used to enhance the optical properties such as brightness,
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whiteness, and gloss of paper and paperboard. Fine clay is used to improve gloss of
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coated paper because it has smaller particle size and a layered structure.
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Dental ceramic materials were polished using water-resistant polishing papers. For
every polishing system, when polishing was sequentially conducted from rough to final
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polishing, the glossiness increased. The type of ceramic and polishing paper were dif-
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fered in regard to achieved result.
The gloss retention of PEEK composites for dental prostheses were evaluated by
toothbrush abrasion. Toothbrush abrasion was performed using 12,000 abrasion cycles at
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load of 200 g. Glossiness correlated with surface roughness. The best results were
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obtained with composite containing filler of smallest particle size (300 nm).
The titanium dioxide coating on denture base materials increased the degree of sur-
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face glossiness, while maintaining the color of the resin denture base.
The gloss intensity of cementitious compositions is often influenced by temperature
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and may decrease at low temperatures. The dull or matt surfaces are sometimes difficult
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to clean, therefore, gloss is often associated with surface smoothness. A higher average
NCO functionality usually leads to glossier products but improved gloss effect can also be
achieved with a lower average NCO functionality of at least 2, if polyol is added to the
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MDI component and reacted.
The UV-curable metallic compositions provide a high gloss metallic finish, retain the
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gloss level over storage duration, and maintain shelf stability. The metallic finishes have