Pencil hardness test

Pencil hardness of the coating was determined using a pencil hardness tester (BYK Gardner) with a calibrated set of drawing leads (M/s Mars Lumograph, Germany). Results of pencil hardness test... 

Using your fingernail is a satisfactory way of determing hardness. If desired a Barcol impressor, or a pencil hardness test may be employed. 

Another mechanical durability test is the pencil hardness test. According to this method a pencil with quantified hardness is dragged on the surface... 

The capilal letters of A B, C and D except for pencil hardness test indicate changeless, stigtitly changed, slightty damaged, and fully damaged of each coloied glass after tests, respectlvety. 

The pencil hardness test is perhaps the simplest form of hardness test and it is the most common hardness test applied to coatings. Pencils are pushed into the sample and the coating hardness is identified by the trace generated. The Elcometer 3080 pencil hardness tester (Fig. 2.22) is supplied with a stand and a series of 14 pencils ranging from 6B (softer) to 6H (harder). This test is an abrasion test, but it is a measure of the coatings abrasion of the pencil lead, not vice versa. 

Although hardness is a somewhat nebulous term, it can be defined in terms of the tensile modulus of elasticity. From a more practical side, it is usually characterized by a combination of three measurable parameters (1) scratch resistance (2) abrasion or mar resistance and (3) indentation under load. To measure scratch resistance or hardness, an approach is where a specimen is moved laterally under a loaded diamond point. The hardness value is expressed as the load divided by the width of the scratch. In other tests, especially in the paint industry, the surface is scratched with lead pencils of different hardnesses. The hardness of the surface is defined by the pencil hardness that first causes a visible scratch. Other tests include a sand-blast spray evaluation. 

Table 14.3 contains comparative hardness values for five hardness scales including the classical Mohs scale, which ranges from the force necessary to indent talc given a value of 1 to that needed to scratch diamond given a Mohs value of 10. In the field, a number of relative tests have been developed to measure relative hardness. The easiest test for scratch hardness is to simply see how hard you have to push your fingernail into a material to indent it. A more reliable approach involves scratching the material with pencils of specified hardness (ASTM-D-3363) and noting the pencil hardness necessary to indent the material. 

Hardness. Hardness has been studied by Pencil Hardness (ASTM D3363-74) and Rocker (Sward) Hardness Test (ASTM D2134-66). Coatings with thickness of about 1.5 mils have been used for Pencil Hardness. Slightly thicker coatings with thickness in the range of 1.5-1.8 mils are used for Rocker Hardness Test. 

The results from both tests show that the coatings hardness is excellent. Pencil hardness is at least 3H. Our equipment, however, does not allow us to measure... 

In the Mohs hardness test, the resistance of the sample to scratching is tested. The Mohs hardness scale is divided into ten degrees of hardness. These are fixed arbitrarily (e.g., talc = 1, Iceland spar = 3, quartz = 7, diamond = 10). A similar hardness scale is based on the scratching power of pencils of different hardness. 

Pencil hardness n. A measure of coating hardness based on the scratching of the film with pencil leads of known hardness. The result is reported as the hardest lead, which will not scratch or cut through the film to the substrate. Paint and coating testing manual (Gardner-Sward Handbook) MNL 17, 14th edn. ASTM, Consho-hocken, PA, 1995. 

HaU effect measurement, 467 hardness measurement in sol-gel coatings aluminium alloy, use of, 304 antireflex coatings, 305 Berkovich indenter, 303, 304 defomation mechanisms, 302 diamond indenter, 302 elastic modulus, 303 indentation testing, 302 indium-tin-oxide coatings, 305 loading-unloading cycle, 303 pencil hardness, 305 Poisson s ratio, 303 silica, 304... 

A commonly used quick characterization of relative hardness is provided by the pencil scratch test [25] in which a series of standardized, sharp pencils are drawn across the coating at a specific angle to find the softest one that causes a scratch. Thus, coating hardness is reported as that of the scratching pencil (e.g. 4B-4H). The test is obviously subject to a certain amount of subjectivity, since it depends on the force applied to the pencil, the pencil consistency (i.e. different manufacturers of pencils make pencils of slightly different hardness), pencil sharpness and inclination. For this reason, pencil hardness should only be used as a comparative measure of coating hardness, when the same person performs the test on a variety of coatings with the same pencils. 

Surface hardness of coatings and molded objects is also measured by scratch and abrasion resistance. In one simple test for painted surfaces, the hardness can be quantified in terms of the pencil hardness (HB, 4H, etc.) that leaves an indentation. As a rule, polymer systems cannot approach the surface hardness of silica glass, which is itself a highly cross-linked structure. Some highly cross-linked laminates do have scratch resistance nearly like that of glass. 

A common apparatus used in the paint industry to measure scratch resistance on smooth surfaces and coatings is the Wolff-Wilbom PencU Hardness Test. Using constant pressure and pencils of varying hardness (usually 6B to 6H), the pencil is held at a fixed angle of 45° to the specimen surface and pushed about 6.5 mm away from the operator under a fixed pressure of 7.5N. This test is repeated using softer lead until one is found that will not cut through the coating or indent the surface. 

Pencil hardness measurements were performed as per the protocol specified in the ASTM D3363 standard. A pencil scratch hardness tester from PPH-I was used to test samples (color chips) of different resins under a load of Ikgf at a temperature of 23°C. Mitsubishi-UNI pencils specified by the JIS S6006 standard were used in the evaluation. The hardness ratings, going from softer to harder, range from 6B to 7H and take the form 6B.3B, 2B, B, HB, F, H, 2H, 3H...7H (B=Black, F=Firm and H=Hard). Scratch resistance was also evaluated using a different method compliant with the ISO 1518 standard. An Erichson Scratch Tester (Type 413) was used to measure the resistance of the material to penetration when scratched with a spherical needle 1mm in diameter under a load of 6N. 

Use a grease pencil to label three large test tubes D (for distilled water), H (for hard water), and... 

Resistance to abrasion is measured by determining the weight loss at the abraded surface. Scratch resistance may be measured by using materials of known hardness to scratch the polymer surface. Pencils with known degrees of hardness may be used for this test. 

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