Page 43 - Handbook of Surface Improvement and Modification

38 Scratch and Mar Resistance

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anti-fouling, and self-cleaning for corrosion inhibition of metallic materials. The smart
coatings demonstrated outstanding barrier properties with scratch resistance, in-situ heal-
ing, superhydrophobicity, superoleophilicity, high optical transmission, thermal stability,
and resistance to strong acids, etc., resulting in the extended service life of the coatings
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and the protected metallic materials. Figure 2.29 show types of damage to which anti-
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corrosive coatings are subjected.
Anticorrosive coating was using polyesteramide resin, functionalized ZnO-Al O -
2
3
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flyash composite and functionalized multiwalled carbon nanotubes. The ZnO-Al O -fly
3
2
ash composite was treated with amine-silane to develop the amino functionality on the
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periphery. The MWCNT’s were treated to develop the carboxyl functionality. The
presence of functionalities permitted chemical bonding, improving the performance of the
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coating. The anti-corrosive properties were improved (impedance value increased from
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100 M (ohms) to 10 G (ohms)). The hardness of the coating increased from H to 4H and
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scratch resistance increased from 2 to 3.1 kg.
Cellulose nanocrystals are an emerging renewable nanomaterial which can be
improved by carbon chain grafting to enhance its dispersion and its ability to transfer its
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rigidity into less polar matrices, especially acrylic wood coatings. Cellulose nanocrystals
were better dispersed in aqueous acrylic coatings (a mean surface roughness falling from 9
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to 6 nm on the coatings containing unmodified cellulose nanocrystals). The modified
cellulose nanocrystals had a higher scratch resistance, with an improvement from 24% to
38% for coatings containing cellulose nanocrystal derivatives over those with unmodified
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cellulose nanocrystals.
An ultra-clear rub and scratch resistant water-based coating provides barrier proper-
ties to film and it is receptive to flexo, litho, and gravure printing inks. It includes polyure-
thane-acrylic hybrid dispersion in combination with melamine formaldehyde resin and
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micronized wax (Neptune 5223N4). The coating can be applied to a wide variety of dif-
ferent polymers such as polyesters, metalized polyesters, polyamides, metalized poly-
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amides, biaxially oriented polypropylene, and others. The micronized wax has an
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average diameter of from about 10 to 12 μm.
An inorganic polysiloxane polymer matrix formed from water-based colloidal silica
and tetraethylorthosilicate was used for making abrasion and scratch resistant UV-block-
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ing glass coating. The resin can also include a bi-functional silanol coupled to the inor-
ganic polysiloxane polymer matrix selected from a group consisting of
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glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane. The resin fur-
ther can include a UV absorber conjugated to the bi-functional silanol coupling agent. 69
The UV absorber can be selected from a benzophenone, benzotriazole, or benzothiazole,
such as Tinuvin 328, Tinuvin, 928, Tinuvin 1130, 2,2'- dihydroxybenzophone, and
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includes 2,2',4,4'-tetrahydroxybenzophenone.
A coating has superior resistance to burnishing even at extremely low gloss, coupled
with great scratch resistance, without compromising either the visual or tactile qualities of
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the finish. The coating contains a linear binder (linear polyester polyol and aromatic/ali-
phatic polyisocyanate) bearing a small proportion of reactive groups for crosslinking, a
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specific mix of crosslinking agents of different reactivity, and a silica matting agent.