Study on Testing Method of Polymer Coating Bonding Energy

The adhesion between the polymer coating and the substrate is the main test indicator of the coating performance. According to national standards, the determination of the adhesion of polymer coatings generally adopts cross-cutting and stripping.

(1) Loading system: The loading system consists of two parts, a displacement sensor and a stress sensor. The displacement is controlled and converted into stress by a stress sensor and loaded directly into the tool, see. The magnitude of the loading G is controlled so that the coating is just scratched, that is, the blade is just in contact with the substrate, but it does not injure the substrate. The G value must be tested repeatedly during the test of adhesion. This is the key to ensure accurate measurement.

(2) The scraping system: The shape of the scraper in the scraping system is shown in the tool system: the scraper cutter head is basically linear, and the cutter head is 1.64 mm wide. To prevent the vibration of the cutter during operation, the front and back angles of the cutter must be strictly controlled. The front and rear corners of the general knife are basically stable at about 10 o'clock.

(3) Traction system: It is necessary to ensure uniform operation of accessories such as cutting tools, stress sensors, and displacement sensors. In this process, due to the influence of frictional inhomogeneity and other factors, the traction force may be at the test method of each parameter in 1.3 (1) Force analysis during the testing process decomposes traction into adhesion, system friction, and polymer coating cohesion, as shown.

Displacement sensor test piece electrical signal system w (force analysis system during coating test of bovine gravitational system friction force is the friction between the base metal and the cutter head and the friction between the wear-resisting block and the polymer coating Sum. In order to eliminate the experimental error, the trajectory in the determination of the adhesion of the coating is reversed and operated at a uniform speed. At this time, the traction force can be approximately considered as the system friction force.

Taking a thermosetting resin coating as an example, it has good adhesion, and its adhesion is measured by cross-hatch method. This shows that the polymer coating has a relatively small cohesion and a relatively large adhesion force. The squeegee was replaced by a cutter, and through the loading system, an electrical signal of approximately 0.5 N was applied and the electrical signal coating had been destroyed. The polymer coating only has a film thickness of 20 to 40 μm. The cohesive force of the polymer resin is relatively small relative to the sum of the friction and adhesion of the system and can be approximately ignored.

2 Test results and analysis 2.1 Microscopic analysis of coating scratches In general, it is difficult to measure the peeling area between the coating and the substrate through a peel test. The decomposition of the tensile force is also difficult to calculate. Therefore, the adhesion was measured using this method. The big limitations are sometimes difficult to characterize. When the adhesive force was measured with a multi-functional coating adhesion tester, the peeling area was more than 99.5%, and the boundary of the damage of the coating was relatively neat. see.

Macromolecule coating stripping sample morphology 2.2 Measurement results of system friction In order to minimize the error caused by the system friction, the scraper under the original load along the track of the coating scratch trace reverse operation, determine the corresponding traction, The system friction. Since the system motion is a process from static to dynamic, there are two parts of static friction and dynamic friction in the motion process, and the general dynamic friction force is smaller than the static friction force. Adhesion is measured after a smooth movement. Therefore, the system friction is dominated by dynamic friction. The specific test data is shown in Table 1. 2.3 Determination of Coating Adhesion The adhesion of the coating is affected by the contact width between the tool tip and the coating, so as to eliminate this influencing factor. The adhesion energy of a layer of adhesive force applied to a unit area under a load means that F is the adhesion force (N), w is the width of the scratches, it can also be approximated as the width of the doctor blade (OT), and five is the bonding energy per unit area kJ. /lrf). Test Number Table 1 Adhesion Test Results Test Results Sample Load Traction System Coating Unit Area Friction Adhesion Surface Energy Iron Red Alkyd Resin Coating Orange Red Acrylic Resin Coating Green Polyester Resin Coating Yellow Nitro Modified Coating The orange-red acrylic resin coating with an anodic electrophoretic primer The orange-colored acrylic resin coating with a cathodic electrophoretic primer can be seen from Table 1. The multifunctional polymer coating adhesion tester can be qualitatively and quantitatively analyzed. The level of adhesion. The coating adhesion of the orange acrylic resin coating of the cathodic electrophoretic primer is significantly higher than that of the orange electroacrylic resin coating of the anode electrophoretic primer; the adhesion of the polymer coating containing the electrophoretic primer is lower than that of the coating coated only with the electrophoretic primer.