Detailed explanation of 3 methods for measuring film flexibility

Film flexibility refers to the comprehensive manifestation of multiple performances such as resilience, plasticity and adhesion exhibited by the film when subjected to external forces. This performance is critical to the performance of coatings in various environments and applications. Flexibility is determined by the composition and material of the Coating, and is also related to the deformation speed and time of the coating during inspection. It can also be evaluated by means of impact resistance and post-formability.

The flexibility of film is not only related to its durability during use, but also directly affects the Appearance and performance of the product. Therefore, in the Coating industry, the determination of flexibility is a crucial work. At present, the commonly used flexibility detection methods include shaft rod tester detection method, cylindrical mandrel Bending tester detection method and cone deflection tester detection method.

Shaft rod tester detection method

Shaft rod tester is a common tool used to measure film flexibility, and its standard is specified in the national standard GB/T 1731-93 "Determination of paint film flexibility". This method uses shaft rods of different diameters with radius of curvature of 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 5.0mm and 7.5mm. During the test, the lacquered tinplate to be tested is placed on shaft rods of different diameters, and the flexibility of the coating is tested by bending. The minimum diameter shaft rod can be used so that the coating does not break after bending, and the number of millimeters of its diameter is the evaluation value of flexibility.

Cylindrical mandrel bending test method

The detection method of the cylindrical mandrel bending tester is specified in the national standard GB 6742-2007 "Paints and varnishes bend test (cylindrical mandrel) ". This method is suitable for test plates with a thickness of less than 0.3mm, and the diameter range of the shaft is wide, including 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 25mm and 32mm. During the test, the test plate is inserted into the shaft, and the coating face is outward, and then the test plate is bent 180 ° in the instrument to observe whether the film is cracked or disbonded. The advantage of this method is that the whole plate test can be carried out, and no direct contact with the coating is required, which eliminates the influence of human body temperature on the test plate.

Detection method of cone deflection tester

The detection method of the conical deflection tester is specified in the national standard GB/T 11185-2009 "Paints and varnishes bend test (conical mandrel) ". The central axis of the instrument is conical and has specific dimensions, including length (203 +/- 3) mm, large head diameter 38mm, and small head diameter 3.1mm. During the test, insert a test sample with a size of 75mm × 150mm into the fixed instrument, and then bend the test plate against the surface of the conical mandrel by turning the upper handle. Under sufficient lighting conditions, use 10x magnifying glass or visually observe whether the coating is cracked or disbonded, and then measure the distance from the thin end of the shaft to the last visible crack, indicating the length of the crack range on the test plate in millimeters.

Flexibility is one of the key indicators in film performance, which is directly related to the durability and service life of the coating. To evaluate the flexibility of the film, different test methods can be used, including the shaft rod tester test method, the cylindrical mandrel Bending tester test method and the cone deflection tester test method. Each method has its applicable situation and advantages, and the choice of the appropriate method depends on the type of Coating, Application and specific requirements. Effective flexibility testing ensures that the film can perform in a variety of environments, thereby protecting the substrate and extending the service life of the product.