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Significance and Use
5.1 Scratch tests are performed on specimens:
5.2 Since polymers exhibit mechanical properties that are strongly dependent on temperature, the test standard prescribed herein is designed to yield reproducible results when users perform tests under the similar testing environment and on specimens of the same material and surface texture that are subjected to the same conditioning procedures.
5.3 Certain polymers are self-healing (recoverable) when subjected to scratches and other physical deformations because of their viscoelastic and relaxation properties. It is important to note the difference between the instantaneous (if readily measurable) and residual scratch damage and compare results appropriately to ensure reproducibility. It is recommended that 24 hours be allowed for viscoelastic recovery when considering residual scratch depth.
5.4 “Whitening” of the scratched surface is a key damage mechanism that has prompted much concern in automotive and other applications where surface aesthetics is important. This type of damage is undesirable because it is evident to the human eye. The critical normal load at which this phenomenon appears serves as a benchmark in ranking material performance, especially from an aesthetic point of view.
1.1 This test method describes a laboratory procedure using an instrumented scratch machine to produce and quantify surface damage under controlled conditions. This test method is able to characterize the scratch resistance of polymers by measuring many significant material parameters. The scratch-inducing and data acquisition process is automated to avoid user-influenced effects that may affect the results.
1.2 The values stated in SI units are to be regarded as standard. The values in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D618 Practice for Conditioning Plastics for Testing
D638 Test Method for Tensile Properties of Plastics
D1894 Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
G99 Test Method for Wear Testing with a Pin-on-Disk Apparatus
G171 Test Method for Scratch Hardness of Materials Using a Diamond Stylus
ICS Number Code 25.220.60 (Organic coatings)