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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 1732-1993 Determination of impact resistance of film. In addition to editorial changes, the following main technical changes have been made with respect to GB/T 1732-1993:
——In normative references, GB 308, GB 708, GB 1727 and GB 1764 are deleted; GB/T 308.1-2013, GB/T 9278, GB/T 13452.2, GB/T 20777 and GB/T 37356 are added (see Clause 2; Clause 2 of Edition 1993);
——The clause “Principle” and clause “Expression of results” are added (see Clause 3 and Clause 8);
——The regulations on punch and steel ball of impact tester are modified (see 4.1; 3.2.2 of Edition 1993);
——The correction method of impact tester is deleted (see 3.4 of Edition 1993);
——The substrate dimension is modified (see 6.1; 5.1 of Edition 1993);
——The distances between the edge of the impact point and the edge of the test panel as well as the edge of adjacent impact points are modified (see 7.3, 6.2 of Edition 1993);
——The requirements for adjusting the height interval of hammer and the lighting conditions for observation of results are added (see 7.3);
——The test report is modified (see Clause 9; Clause 7 of Edition 1993);
This standard was proposed by China Petroleum and Chemical Industry Association.
This standard is under the jurisdiction of National Technical Committee 5 on Paints & Pigments of Standardization Administration of China (SAC/TC 5).
The previous editions of this standard are as follows:
——GB 1732-1979 and GB/T 1732-1993.
Determination of impact resistance of coating films
1 Scope
This standard specifies the test method for determining the impact resistance of coating films by the maximum height (in cm) of the hammer of a fixed mass falling on the punch without causing any coating film damage when the punch hits the test panel.
This standard is applicable to the determination of impact resistance performance of coating films.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 308.1-2013 Rolling bearings - Balls - Part 1: Steel balls
GB/T 3186 Paints, varnishes and raw materials for paints and varnishes - Sampling
GB/T 9271 Paints and varnishes - Standard panels for testing
GB/T 9278 Temperatures and humidities for conditioning and testing of paint specimens
GB/T 13452.2 Paints and varnishes - Determination of film thickness
GB/T 20777 Paints and varnishes - Examination and preparation of samples for testing
GB/T 37356 Paints and varnishes - Lighting and procedure for visual assessments of coatings
3 Principle
Coat the sample under test to applicable metal substrate, and after curing, drop a hammer of fixed mass from a certain height to impact the punch, so that the coating film and substrate are deformed. It may be forward punching (with coating film upwards) or backward punching (with coating film downwards). By gradually increasing the falling height of the hammer, the numerical points where the coating film is liable to damage are determined.
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4 Instruments and equipment
4.1 Impact tester
The maximum scale of the guide tube is (50.0±0.1)cm with graduation of 1cm, and the weight of the hammer is (1,000±1)g, which may move freely in the guide tube. The steel ball on the punch has a diameter of (8.000±0.015)mm and a hardness (HRC) of 61 ~ 66, which shall meet the requirements of GB/T 308.1-2013. The center of the impact is aligned with that of die groove with the depth of punch into the groove of (2.0±0.1)mm; the die groove whose diameter is (15.0±0.3)mm shall be smooth; the radius of curvature of groove edge is 2.5mm~3.0mm. The impact tester is shown in Figure 1.
Key:
1——guide tube
2——hammer controller
3——graduation line
4——punch guide groove
5——die
6——base
7——support
8——punch
9——guide tube
10——hammer
Figure 1 Schematic diagram of impact tester
4.2 Magnifier
4X magnifier.
5 Sample
Take a representative sample of the product under test (or each product in the case of a multi-coat system) as described in GB/T 3186.
Examine and prepare each sample for testing, as described in GB/T 20777.
6 Test panels
6.1 Substrate
Unless otherwise specified, the substrate is tinplate or steel plate, which shall meet the technical requirements of GB/T 9271, and whose dimension shall be 120mm× 50mm× (0.20mm ~ 0.30mm) and 150mm×70mm×(0.45mm~0.55mm) respectively.
6.2 Treatment of substrate and coating of test panel
Unless otherwise specified, treat each test substrate in accordance with GB/T 9271 and then coat the product or system under test by the specified method.
6.3 Drying and conditioning
Dry (or stove) and cure each coated test panel for the specified time under the specified conditions. Test panels that are not cured under the conditions specified in GB/T 9278, when drying, shall be conditioned for at least 16h under the conditions specified in GB/T 9278 before testing.
6.4 Thickness of coating film
The thickness of coating films shall be specified or agreed. The thickness of coating films shall be determined according to one of the determination methods for dry film thickness specified in GB/T 13452.2 and expressed in micrometers (μm).
Foreword i
1 Scope
2 Normative references
3 Principle
4 Instruments and equipment
5 Sample
6 Test panels
7 Test procedures
8 Expression of results
9 Test report
