Page 40 - Handbook of Surface Improvement and Modification

2.4 Properties and Application data 35

tensile stresses formed as a result of coating shrinkage during the drying process and
56
cracking.
Atomic layer deposition was studied for ultra-thin (100 nm) barrier coating deposi-
57
tion onto organic photovoltaics to enhance device lifetime. The higher organic content in
the AlO film enhanced the interfacial bonding at the AlO –organic photovoltaics inter-
x
x
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face and it also impeded fracture propagation.
Plasma enhanced chemical vapor deposition technology permits deposition of a coat-
58
ing on larger surface areas. Coatings applied using this method show good adhesion and
scratch resistance, but the deposi-
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tion rate is still low. Employing
microwave power can increase the
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deposition rates. More informa-
tion on the application of thin
coatings on optical materials can
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be found in a review chapter.
The uppermost layer of auto-
motive coating is a clearcoat hav-
ing a thickness ranging from 5 to
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50 μm. Its role is to protect
underlying layers from chemical,
UV degradation, and mechanical
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damage. The most prone to
scratching parts of the vehicle
include the exterior paint finish,
small exterior trim pieces such as
door handle pockets or pillar
appliques, and interior trim com-
59
ponents. The car wash scratches
are only a few microns in width
and depth, and they do not frac-
59
ture the clearcoat. The deep and
wide scratches are caused by tree
branches, keys, and shopping
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carts. These scratches may lead
to fracture of the clearcoat and the
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underlying layers. Discussion of
various aspects of automotive
coatings is avaialble in the review
59
article.
Polycarbonates are widely
Figure 2.27. The principle of Lego design in development of dura-
ble coating for polycarbonate. [Adapted, by permission, from used because of their transparency,
Barletta, M; Puopolo, M; Gisario, A; Vesco, S, Prog. Org. Coat., toughness, ductility, and chemical
101, 161-77, 2016.] 60
inertness. They are ideal candi-
dates to substitute float glasses, where lightweight and safety are of utmost relevance but
60
they have a limited scratch and mar resistance due to a very low surface hardness. This is