The paint film or ink film adhesion refers to the ability of the paint film or ink film and the surface of the adhered object to adhere to each other through physical and chemical action. From a practical point of view, adhesion refers to the force required for the paint film or ink film to be removed from the print. This force is the paint film or the ink film and the base film.
Bonding bond strength. The adhesion of the paint film or ink film is one of the important indicators for assessing the performance of the paint film or ink film. Only the paint film or ink film has a certain adhesion, and it can adhere well to the surface of the base body. Will play the role of paint or ink adhesion and protection, to achieve the purpose of applying paint or ink.
First, the film or ink film adhesion mechanism
There are two kinds of adhesion mechanisms of paint film or ink film: mechanical adhesion and chemical adhesion. Mechanical adhesion depends on the nature of the base acquisition (roughness, porosity) and the strength of the paint film or ink film formed. Chemical adhesion refers to the mutual attractiveness of the interface film or ink film molecules and the base-collecting molecules between the paint film or the ink film and the base film, and depends on the physical and chemical properties of the paint film or the ink film and the base film.
When people explain the adhesion mechanism of the paint film or ink film, it is generally believed that the chemical attachment theory is more realistic. Among the cohesive forces that are chemically attached, include electrostatic forces, van der Waals attractive forces, hydrogen bonding forces, and chemical affinities. These forces determine the adhesion of paint or ink to the surface of the base body:
1. The degree of wetting of an object by a liquid film-forming substance;
2. Formation of a directional adsorption layer on a solid surface;
3. A two-electron layer caused by the boundary between the film formation and the solid surface during the formation of the paint film or ink film.
Therefore, in the study of the adhesion of the paint film or ink film, determine the kind of paint film or ink film tear off from the object
Type is very important and can be roughly divided into the following three types.
(1) Adhesion type: The paint film or ink film completely falls off the surface.
(2) Cohesive type: The paint film or ink film is cracked or lifted, and the adhesive force is greater than the cohesive force.
(3) Mixed type: The paint film or the ink film partially falls off from the surface, that is, the paint film or the ink film itself is partially split, and the adhesive force is close to the cohesive force.
It is generally believed that the adhesion of the paint film or ink film depends on the polar group of the polymer (or lower molecular weight prepolymer) in the film-forming substance, such as -OH, or - the polar group of the COOH and the base surface In order to combine these polar groups with each other, polymer molecules must be required to have a certain degree of fluidity, so that the polymer molecules can better wet the base mining surface, so that the polar groups of the polymer are close to being The polar surface of the imprinting surface, when the distance between the two molecules becomes very small (reaches within 1 A), the adhesion equilibrium between the polar groups due to van der Waals forces or hydrogen bonding.
Second, the method of measuring paint film or ink film
We use two kinds of paint film or ink film adhesion measurement methods: one is the direct determination method for the force required to separate the paint film or the ink film from the surface of the print, and the other is the paint film or the ink film in other. Indirect measurement method for performance measurement.
1 . Direct adhesion measurement method
(1) Twist method (peel test method)
(2) Pulling method
(3) Ultrasonic Oscillation Test
(4) Ultracentrifuge adhesion test
(5) B, B Adria adhesion test
(6) Adhesion test method
2. Indirect adhesion assay
(1) Determine the adhesion of paint film or ink film on a press
(2) Method for determining the flexural strength and elasticity of a paint film or ink film
(3) Determination of adhesion of paint film or ink film by knife cutting