0 Preface
Vacuum coating is a 10-3 ~ 10-4Pa degree of vacuum, using a certain heating method, the vaporization of coating material, fly to the surface of the workpiece (substrate) agglomerated film forming process [1]. Vacuum coating is inseparable from high-tech science and technology. It belongs to the category of new materials and new processes. It is an emerging coating technology in surface engineering technology [2], which enables the wear resistance or radiation resistance of the surface and the entire surface to improve the conductivity of the surface. Or insulation, permeability or electromagnetic shielding and decorative, etc. [2]. The process itself is also relatively friendly to the environment, and waste emissions are minimal, resulting in electronic, optical lens processing, five
Gold device production, jewelry processing and other industries have been widely used.
In some electronic and optical products, in order to function as a signal shield and to prevent external interference, vacuum aluminum plating is often required on the surface of the insulating material, and its advantages are low cost and good effect. However, vacuum metallization is performed on the surface of non-metallic materials, especially vacuum aluminum plating on the surface of a smooth insulating paint. Although the appearance of the coating looks smooth, bright, and beautiful, the adhesion of the coating is often poor. In vacuum aluminum plating on the surface of a certain type of product insulation layer, the adhesion of aluminum plating layer is caused because the surface of the insulation layer is very smooth.
Extremely bad, completely peeled off with tape. If the microscopic structure of the inorganic-organic interface is improved, a series of properties such as adsorption, wetting, and dispersion will change significantly, resulting in a significant increase in the binding force and binding strength [3]. Therefore, we tried to use a surface treatment agent to improve the adhesion of the coating on the surface of the insulating paint. Since no practical application in this area has been performed before, it is necessary to fully test the practical application effect of the surface treatment agent. Through experiments, we determined that this approach is feasible.
l Equipment and materials
The main equipment: vacuum coating machine (DM-450 type).
Material: C30-1l alkyd insulating paint, KH-550 silane coupling agent, GC-100 silicone primer, NJD-9/NJD-11 primer, DG-3S epoxy adhesive, 600 mesh metallographic sandpaper, 3M Paper tapes, tinplates, etc.
2 test
2.1 sample preparation
Spray the C30-11 alkyd insulation paint on the surface of the tinplate piece with the size of 120mm×60mm twice. After the paint film is fully dried, the tinplates coated with the insulating paint shall be grouped: The surface paint layer of the first group is not treated. Blank sample; Group 2 surface is lightly polished with 600 mesh metallographic sandpaper, and a powder is blown clean with a hair dryer; Group 3 is coated with a layer of GC-100 on the surface and allowed to dry for 30 minutes; Group 4 is coated with a layer of NJD-9. After drying for 20 minutes, apply a layer of NJD-ll and air dry. Apply a layer of KH-550 to the surface of Group 5 and allow to dry. Apply Group 1 DG-3S epoxy adhesive to the surface of Group 6.
2.2 Vacuum coating
The 6 groups of samples in 2.1 were taped to the sample holder to ensure that the surface of the lacquer layer was exposed and placed in the coating machine downwards. When the vacuum was applied, the temperature was raised to 80°C and baked for about 1 hour until the vacuum reached 3×10. -3Pa, coating.
2.3 Adhesion test
The cross-cut method in the coating test method was used to cut the grid spacing. The paper was used to pull off the cross-cut surface and check the debonding condition of the coating.
2.4 Environmental Test
The high and low temperature test conditions are as follows: first, the test piece is kept at 30°C at 60°C, and then 30min is maintained immediately at -60°C. The boiling water resistance test conditions were that the test piece was kept in boiling water for 5 minutes. The coating adhesion of the GC-100 sample under two conditions was tested.
3 Results and Discussion
3.1 Test results
The coating appearance and adhesion test of each group of specimens are shown in Table 1 and Figure 1. The test results of the appearance and adhesion of the specimens of the third group coated with GC-100 after the high-low temperature and boiling water resistance tests are shown in Table 2.
Table 1 Coating appearance and adhesion of different surface treatments
Figure 1 coating appearance and adhesion test results
Table 2 Coating appearance and adhesion after environmental test
3.2 Discussion
From the film appearance and adhesion test results, without the surface treatment, the appearance of the coating is bright and flat, the appearance of the best quality, this is because the surface of the insulating paint is good, so the surface finish of the coating is high, basically On the mirror. However, due to the high surface finish of the insulating paint, the bonding force of the coating is also the worst, and the coating is completely peeled off by the paper tape.
After the polished sample, the surface is also relatively flat, but because the bottom surface is rough, although the coating is not substantially off, but it causes the coating lack of brightness, not beautiful. Moreover, in the process of sanding the insulation layer with sandpaper, the sandpaper is harder and has greater damage to the surface of the insulation layer. Samples treated with the GC-100 silicone rubber primer were bright and smooth and did not peel off under the effect of the paper tape, indicating that the surface treatment agent was effective in enhancing the adhesion of the coating. There is a small amount of flower streaks in the coating.
The reason may be due to too much smearing at one time, and the solvent contained in the primer coating slightly dissolves the surface of the insulating layer, thus forming a fine smear during the smearing process. As long as the amount of smearing of the primer is controlled, the generation of flower streaks should be avoided. After the coating was tested by high and low temperature and boiling, there was no obvious change in film appearance and adhesion. It has withstood the more severe environmental tests.
After NJD-9 and NJD · ll primer treatment of the sample, the coating is bright and smooth, striped, the cause of the striation should be with the GC. 100 is the same. The coating layer completely peeled off, indicating that this titanate coupling agent has no effect on enhancing the adhesion of the coating.
In the sample treated with KH-550, the coating surface was flat, but there was a lot of spotting. When the adhesion was measured, it was found that the film layer in the smooth and bright place completely fell off and the spot did not fall off. Combined with the analysis of the phenomena generated during the sample preparation process. The occurrence of spotting and the difference in adhesion should be caused by poor wettability of the coupling agent on the surface of the insulating paint. Due to poor wettability, the coupling agent coated on the surface of the insulating paint gathers into many small liquid spots. The surface of the paint film is not completely covered by the coupling agent.
Samples coated with DG-3S epoxy adhesive showed almost the same adhesion as the polished samples, and no significant peeling occurred. Due to the large viscosity of the adhesive, the applied adhesive layer is not even, so the coated surface is rough. At the same time, due to the inclusion of air, the formation of larger pores in the surface of the adhesive layer, the coating can not be completely covered, thus leaving a pore in the coating surface.
Looking at the five treatment methods, it can be clearly seen that the use of GC-100 silicone rubber primer treatment of the insulating paint surface, regardless of coating appearance, or coating adhesion is ideal.
4 Conclusion
By comparing the appearance and adhesion of the blank sample and the coating obtained with 5 different treatments, it can be confirmed that the use of the silane surface treatment agent GC-100 silicone primer can effectively enhance the adhesion between the coating and the insulating paint. The coating with GC-100 enhanced adhesion did not show significant changes in appearance and adhesion after high and low temperature and boiling tests.