1. Scratch hardness method
Use the method of marking or scratching the coating film with a hard object on the surface of the coating film to measure the hardness of the coating film. Commonly used are the pencil hardness method and the scratch needle method.
The pencil hardness method has two methods: manual operation and instrument test. It uses a pencil with known hardness to measure the hardness of the coating film. Hardness (instrumental test) is used as the hardness of the coating film. Pencils should be high-grade drawing pencils that meet the standards manufactured by regulated manufacturers, and the pen cores should be cut out according to regulations. Different countries adopt different pencil hardness grading. CHINA's national standard CB/T 6739-86 "Measurement Method of Coating Hardness Pencil" stipulates that the pencils used are 13 grades from 6H to 6B, 6H is the hardest, and 6B is the softest. As an arbitration test, the instrument test force method is used, and the general instrument model is the QHQ pencil method rowing boat Hardness Tester.
The scratch test method uses the needle tip of the instrument to scratch the coating film, and uses the scratch resistance of the coating film to represent the hardness of the coating film. It is expressed by whether it is penetrated by the stylus under the specified load, or the minimum load required for the stylus to penetrate the coating. CHINA's national standard "GBT 9279-88 Paint and Varnish Scratch Test" stipulates that an automatic instrument is used as the instrument for the arbitration test, and the results obtained are relatively accurate. When the hardness is measured by the scratch method, the coating film is not only affected by pressure, but also by shear force, which also reflects the adhesion of the coating film. Therefore, the hardness of the coating film measured by it is different from that of the pendulum Suini test method. of.
2. Indentation hardness method
Use a certain quality indenter to press into the coating film, and measure the hardness of the coating film from the length or area of the indentation. The national standard "CB/T 9275-88 Buckholz indentation test for paints and varnishes" stipulates the method of using the Bucholz Tester to test the hardness of the coating film. The measured indentation length shows the hardness of the coating film. The resistance of a layer to indentation by an indenter of an instrument . The indentation hardness is more obvious in the hard film, and the general result is related to the thickness of the coating film. For , the indentation hardness value of the thin film is higher than that of the thick film. From actual measurements, the indentation test is inaccurate for elastic coatings .
