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Deformation Resistance Scatch

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Deformation Resistance Scatch

Physical properties of paint and coatings play an important role in the quality control. Depending on the application a coating is supposed to be extremely hard and rigid such as for example the coating on the hull of an ice-breaker. Automotive coatings however require a certain flexibility since the thin sheet metal of a car body is not fully r...

Physical properties of paint and coatings play an important role in the quality control. Depending on the application a coating is supposed to be extremely hard and rigid such as for example the coating on the hull of an ice-breaker. Automotive coatings however require a certain flexibility since the thin sheet metal of a car body is not fully rigid and a slamming hood should not cause the paint to break. Coil coated steel that is to be formed into products such as white goods or cladding should have excellent forming properties. 

Several empirical tests 
There are a number of different empirical tests that are used to deform test panels and so assess the deformation resistance or flexibility. Coatings that fail such a test will crack and/or detach from the substrate. Also there is quite some overlap between different test systems and their results. Many tests provide information about similar parameters such as elasticity / forming resistance, adhesion, hardness, brittleness, stress resistance etc.. 

Although some tests overlap there is no cross-reference for their results. 

More information can be found in the section hardness/scratch resistance

Commonly used tests
Common tests used in the paint and coatings industry are: 

    • Bend test
      With this system a coated test panel or lacquered sheet metal is bent over a defined mandrel. Cylindrical mandrels in different diameters or conical mandrels are used. 

      The smaller the diameter the sharper the forming of the test panel which leads to elongation of the panel including the coating. A sharper deforming causes more stress to the coating which may lead to cracks or adhesion failure. 

      Cylindrical bend test are recognised to be more precise in comparison to conical bend tests which have the advantage that a range of mandrel diameters can be checked on just one panel.
    • Impact Test, or tubular impact test
      With an impact test a rapid deformation of a painted test panel is generated. A specified weight with a specified punch is dropped on a test panel from different heights. The damage on the sample is observed after the test and provides information about physical properties of the coating such as elasticity, hardness and adhesion. 

      For the paint industry there are different tests according ISO 6272 , ASTM D2794 and others. Each standard has its own specifics such as weight, punch shape, direct or indirect impact etc..
  • Cupping test 
    Cupping testers generate, in contradiction to impact testers, a gradual deformation of the sample. An indenter with a specified shape is slowly forced through the test panel under standardised conditions. During the deformation the panel is visually observed. The cupping value of a coating is the deformation point at which the coating starts to crack. 
    To perform this test correctly it is of utmost importance that the deformation is made gradually without any interruptions.
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Subcategories

  • Scratch and Wear Resistance

    Hardness / Scratch Resistance
    The property of a substance that is resistant to repeated rubbing or scratching. In general, it meant the resistance of a (coating) layer or surface against mechanical friction. Abrasion of products is a concept that can't be handled in general. One must explicitly specify the conditions under which the product must be durable.

    Any change in wear conditions, the assessment of the wear thoroughly change. In general we distinguish wear as single or repetitive. In the former case, a small contamination in the long run leads to serious damage. By repeating is meant the resistance of a surface under prolonged load. The lowering of the coefficient of friction can give a significant improvement. For the determination of the abrasion resistance it should be practical to approach conditions as much as possible. 

    Forms of wear or scratch resistance are e.g. brush abrasion testing, rotating abrasion testing, rub testing, sand fall testing and or shear tests.

  • Hardness of the coatings

    Hardness
    The determination of the reactive resistance, the hardness of a surface of which a coating or alternative protective layer is provided. As with abrasion and scratch resistance there should be an explicit reference given to the hardness meant. Under the hardness of the coatings is in general understood the impression value at which a deformation of the coating occurs. This is determined by pressing sharp or blunt stylus, depending on the material or coating, into the surface.

    Another method to measure hardness is the determination of rolling resistance of a coated surface. The equipment required is using spheres that find resistance during the rolling movement on the test surface i.e. Pendulum hardness. The degree of hardness determines on the number of movements by a pendulum roller experiencing resistance during this process.

    Other types of hardness tests are, Barcol Impression, Shore A-D, Sclerometer and Wolf-Wilburn pencil scratch resistance determination and Persoz or Konig pendulum hardness testers.

  • Deformation resistance - Elasticity

    Commonly used tests used in the paint and coatings industry are: 

      • Bend test
        With this system a coated test panel or lacquered sheet metal is bent over a defined mandrel. Cylindrical mandrels in different diameters or conical mandrels are used. 
        The smaller the diameter the sharper the forming of the test panel which leads to elongation of the panel including the coating. A sharper deforming causes more stress to the coating which may lead to cracks or adhesion failure. 
        Cylindrical bend test are recognised to be more precise in comparison to conical bend tests which have the advantage that a range of mandrel diameters can be checked on just one panel.
      • Impact Test, or tubular impact test
        With an impact test a rapid deformation of a painted test panel is generated. A specified weight with a specified punch is dropped on a test panel from different heights. The damage on the sample is observed after the test and provides information about physical properties of the coating such as elasticity, hardness and adhesion. 

        For the paint industry there are different tests according ISO 6272 , ASTM D2794 and others. Each standard has its own specifics such as weight, punch shape, direct or indirect impact etc..
    • Cupping test 
      Cupping testers generate, in contradiction to impact testers, a gradual deformation of the sample. An indenter with a specified shape is slowly forced through the test panel under standardised conditions. During the deformation the panel is visually observed. The cupping value of a coating is the deformation point at which the coating starts to crack. 
      To perform this test correctly it is of utmost importance that the deformation is made gradually without any interruptions.
  • The TQC Bend Test Conical Mandrel "Pro" is a laboratory apparatus to bend coated test panels over a conical shaped mandrel in order to assess the elasticity or resistance of a coating-, paint or varnish to cracking, elongation and/or detachment from a metal test panel in accordance with ISO 6860 and ASTM D522. The conical shape of the bending area allows...

  • Koh-I-Noor 1500 set of 20 pencils in an aluminum case to use with the Wolff Wilborn Hardness Test. Pencils ranging from 8b to 10H (8B, 7B, 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, 10H)

  • The TQC Pencil Hardness Test according Wolff Wilborn provides in a simple method to test the scratch hardness of coatings. In this test, pencils in a range of 6B to 8H hardness-grade are used. The pencil is moved scratching over the surface under a 45° angle with a constant pressure. Then an optical assessment is carried out to see which pencil hardness...

  • The TQC Hardness Pen is a pocket instrument for testing the hardness and wear/scratch resistance of materials such as coatings, lacquers, plastics or related products. A tungsten carbide tip is drawn over the surface with a defined constant pressure. The pressure on the tip can be changed using the slide or by changing the spring. A visual mark on the...

  • The TQC Pendulum Hardness Tester has a lot of unique features that ease defining hardness by the König and/or Persoz method as described in ISO 1522. Both methods work on the principle that the damping time of a pendulum oscillating on a sample indicates the hardness.

  • The TQC Buchholz Hardness Indentation Test provides a method for carrying out an indentation test on coatings complying with the ISO 2815-2003 standard. The TQC Buchholz Hardness Indentation Test consists of a calibrated slip-on weight with a sharp-edged metal wheel, an illuminated microscope, a level gauge, a digital dual timer, and two markers with...

  • The TQC Impact Test is used to determine the impact resistivity and flexibility of coatings. The dual scale instrument is equipped with a special guidance which assures that the distance between each impact is always according to the standard. For correct positioning a spirit-level is built-in. Each Impact test comes as a complete set (instrument and...

  • The PosiTector SHD Shore Hardnesss Durometer is a handheld electronic instrument that measures the indentation hardness of non-metallic materials. Two durometer models are available for different hardness ranges - Shore A and Shore D.

  • The TQC Shore Hardness Gauge is a reliable instrument for measuring the impression hardness of soft materials such as coatings, plastics and rubber. Equipped with a drag indicator, which holds the highest measured result. Delivery includes a simple test block. 

  • TQC scrub / washability test now custom configurable TQC Abrasion scrub/ washability Test to perform an abrasion and washability  test on coated panels to define the resistance of paint, varnish or related products to scratching, wearing and colour loss due to wet or dry abrasion. Simulating everyday wear from cleaning actions or general use.

  • Taber Abrasion is used to determine relative resistance to abrasion defined as ‘the ability of a material to withstand mechanical damage’ such as rubbing, scraping or erosion. The Taber Abraser is an industry standard used in the wear and durability testing of parquet, metals, leather, textiles, rubber, lacquered surfaces, carpets, coatings etc..

  • The TABER ® Multi-Finger Scratch / Mar Tester is used to measure the relative resistance or susceptibility of a material surface to scratching, marring, gouging, scraping, engraving and other similar physical damage that can’t be classified as ordinary wear.

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