Page 18 - Handbook of Surface Improvement and Modification

2.1 Methods and mechanisms of protection 13

Figure 2.12. The scratch damage mechanisms: (a) Groove formation; (b) Periodic micro-cracking; and
(c) Plowing. [Adapted, by permission, from Browning, R; Sue, H-J; Minkwitz, R; Charoensirisomboon, P,
Polym. Eng. Sci., 51, 2282-94, 2011.]
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lulose. The scratch resistance of coated wood specimens was improved by up to 25%. 22
Also, coating hardness was slightly higher for nanocellulose-filled coatings as revealed by
22
nanoindentation.
Plasma-enhanced chemical vapor deposition was used for application of three-layer
23
scratch-resistant hydrophobic and oleophobic coating. The first SiO layer was coated
x
on the substrate using octamethylcyclotetrasiloxane, followed by oxygen plasma treat-
23
ment. The hydrocarbon-based hydrophobic film was synthesized using hexamethyldisi-
23
lane, as the second layer; the CF -based film was coated using C F . The water contact
x
2 6
o 23
23
o
angle was 110-115 and the oil contact angle was 84 . The pencil hardness was 7H.
The fundamental understanding of the scratch behavior of styrene-acrylonitrile ran-
dom copolymers was pursued using the methodology outlined in ASTM D7027-05/ISO
1
19252:08. The key scratch damage mechanisms (scratch groove formation, periodic
1
micro-cracking, and plowing) were identified (Figure 2.12). The mechanisms are related
1
to the mechanical properties of the SAN model systems. The progressive load methodol-
ogy of the ASTM/ISO scratch test provides valuable insight to the fundamentals of the
1
polymer scratch process.
Healing is considered to be very suitable method of resolving problems related to
product damage, especially when damage is limited. Although, the idea of healing was
taken from living things, its in extenso application to man-made materials is insufficient
because in the living things healing leaves scars and scars do not appeal to users of man-
made materials. A book entitles Self-healing Materials. Principles & Technology has
24
just been published. It deals with various aspects of self-healing of polymeric materi-
24
als. It should be consulted by those who need extensive information and background. 24
In this book we present two cases of self-healing of scratched surfaces as examples of
potentially available technology.
Tribological properties and scratch healing of a typical automotive clearcoat modi-
25
fied by a polyhedral oligomeric silsesquioxane compound have been studied. The OH-
functionalized polyhedral oligomeric silsesquioxane nano-structures were added to
25
improve the scratch resistance of an acrylic melamine clearcoat. The incorporation of