Page 35 - Handbook of Surface Improvement and Modification

30 Scratch and Mar Resistance

intermediate zirconia-to-silica ratio show excellent mechanical strength, high level of
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hardness and superior integrity after long-term light exposure.
2.2 METHODS OF TESTING

Many standardized testing techniques for scratch and mar resistance of plastics are avail-
able, including
ASTM D7027-13 Standard Test Method for Evaluation of Scratch Resistance of Poly-
meric Coatings and Plastics Using an Instrumented Scratch Machine
ASTM G171 - 03(2009)e2 Standard Test Method for Scratch Hardness of Materials Using
a Diamond Stylus
ASTM F2496-05(2011)e1 Standard Practice for Determining the Scratch Hardness and
Scrape Adhesion of Prints and Coatings
ASTM C1624-05(2015) Standard Test Method for Adhesion Strength and Mechanical
Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing
ASTM D7187-15 Standard Test Method for Measuring Mechanistic Aspects of Scratch/
Mar Behavior of Paint Coatings by Nanoscratching
ASTM F428-09(2014) Standard Test Method for Intensity of Scratches on Aerospace
Glass Enclosures
ASTM F548-09(2014) Standard Test Method for Intensity of Scratches on Aerospace
Transparent Plastics
ASTM D3363-05(2011)e2 Standard Test Method for Film Hardness by Pencil Test
ISO 17541:2014 Plastics -- Quantitative evaluation of scratch-induced damage and
scratch visibility
ISO 1518-1:2011 Paints and varnishes -- Determination of scratch resistance -- Part 1:
Constant-loading method
ISO 1518-2:2011 Paints and varnishes -- Determination of scratch resistance -- Part 2:
Variable-loading method
ISO 18922:2003 Imaging materials -- Processed photographic films -- Methods for deter-
mining scratch resistance
ISO 19252:2008 Plastics -- Determination of scratch properties
ISO 20566:2013 Paints and varnishes -- Determination of the scratch resistance of a coat-
ing system using a laboratory-scale car-wash
ISO 12137:2011 Paints and varnishes -- Determination of mar resistance
ISO/TC 61/SC 2 Mechanical behavior
The above list does not include many industrial standards developed by companies
involved in the use of paints and coatings, such as, for example, car manufacturers.
Some of the above testing methods have been used in research projects aiming at the
improvement of scratch and mar resistance of paints and coatings and these are discussed
below.
Scratch tests use a sharp objects which are pressed onto, and drawn over the surface
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of the coating. The normal load is kept constant or progressively increased. The pro-
gressively increased load in scratch test determines a critical point of damage such as coat-
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ing delamination, cracking, or whitening. The critical load or its derivative is used to
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compare the performance of different coatings.