Standard Test Method for Resistance of Transparent Plastics to Surface Abrasion
Transparent plastic materials, when used as windows or enclosures, are subject to wiping and cleaning; hence the maintenance of optical quality of a material after abrasion is important. It is the purpose of this test method to provide a means of estimating the resistance of such materials to this type and degree of abrasion.
Although this test method does not provide fundamental data, it is suitable for grading materials relative to this type of abrasion in a manner which correlates with service.
Comparison of interlaboratory data or the specification of a “haze” value has no significance if the hazemeter requirements given in 5.4 are not used. This is because light diffused from the surface of a Taber track is scattered at a narrow angle (Fig. 1 and Fig. 2) while light diffused internally by a specimen is scattered at a wide angle. In many hazemeters, when a diaphragm is inserted to limit the light beam to the width of the abraded track, the specular beam at the exit port becomes smaller. The dark annulus will then be greater than the 0.023 ± 0.002 rad (1.3 ± 0.1°) requirements of Test Method D1003. Since a large percentage of the narrow-angle forward-scattered light will not impinge on the sphere wall, “haze” readings become smaller. For hazemeters that have not been properly adjusted, the magnitude of this reduction is dependent both on the integrating sphere diameter and the reduction of the entrance beam.
For many materials, there may be a specification that requires the use of this test method, but with some procedural modifications that take precedence when adhering to the specification. Therefore, it is advisable to refer to that material specification before using this test method. Table 1 of Classification System D4000 lists the ASTM materials standards that currently exist.
For some materials, abrasion tests utilizing the Taber abraser may be subject to variation due to changes in the abrasive characteristics of the wheel during testing.
Depending on abradant type and test specimen, the wheel surface may change (that is, become clogged) due to the pick up of coating or other materials from test specimens and must be cleaned at frequent intervals.
The type of material being tested and the number of test cycles being run is known to sometimes influence the temperature of the running surface of the wheel with an affect on the final haze measurement. To reduce any variability due to this temperature effect, stabilize the wheels surface temperature prior to performing actual measurements. This shall be accomplished by conducting multiple refacings on an ST-11 refacing stone, followed by a test on the sample material to be tested (with results to be discarded).
Note—This photograph shows light pattern of the scattering from the surface of a Taber abraded specimen. The circles show how increasing the 1.3° dark annulus dramatically changes the amount of light impacting the sphere wall.
Note—This graph shows goniophotometric curves for Taber abraded tracks. The specular angle of transmission is at 180°.
1.1 This test method describes a procedure for estimating the resistance of transparent plastics to one kind of surface abrasion by measuring the change in optical properties.
1.2 Abrasive damage is visually judged and numerically quantified by the difference in haze percentage in accordance with Test Method D1003 between an abraded and unabraded specimen.
1.3 CS-10F wheels manufactured between October 2002 and September 2004 have been found to give different results than historical values. Comparisons of data using these wheels should be made with caution. Results using wheels made after September 2004 have agreed with those obtained before October 2002.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
Note 1—This test method is equivalent to ISO 3537 in the measurement of resistance to abrasion in Section 7, but is not equivalent to ISO 3537 in any other measurement or section. This test method is not equivalent to ISO 9352, and results cannot be directly compared between the two methods.
Note 2—This test method is similar to ANSI/SAE Z26.1, Test 17.
Note 3—Prior attempts to employ the Taber Abraser for volume loss determinations of various plastics have been unsuccessful because of excessively large coefficients of variation attributed to the data. Insufficient agreement among the participating laboratories has rendered the use of volume loss procedure inadvisable as an ASTM test method.
Note 4—For determining the resistance to abrasion of organic coatings by weight loss, reference is made to Test Method D4060, which uses more aggressive CS-10 or CS-17 abrasive wheels. It suffers from poor reproducibility between laboratories when numerical abrasion resistance values are used. Interlaboratory agreement improves significantly when ranking a series of coatings for their abrasion resistance.
1.5 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.
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