3.2 effect of different coupling agents on sol stability and coating adhesion






The influence of KH-550, KH-560 and KH-570 on the stability of sol and the adhesion of coating without coupling agent is studied as shown in Table 2.






There is no strong binding between pure organic oxide film and epoxy resin. The coupling agent of silicon and Anhui is introduced into the CL containing adhesive. After hydrolysis, organosilicon compound film is formed on the surface of components. The binding strength depends on the affinity of polar chain. Taking KH-560 as an example, its chemical equation is as follows:






Thus, Si02 produced by hydrolysis of silicic acid and acetic acid and silicone network produced by hydrolysis of silicic acid and coupling agent can be formed at a lower temperature, which not only helps the combination of silicone film and resin substrate, but also maintains the wear resistance of inorganic silicon oxide. Of course, in order to improve the wear resistance of the coating under the condition of meeting the adhesion, the proportion of the silicoacetic acid and the silicon burning coupling agent in the coating solution must meet certain requirements.






It can also be seen from table 2 that when KH-550 is used as coupling agent, the stability of banyan gum is poor, and the gelling time is less than 2D (generally, the interval from the beginning of aging to the non flow of inclined liquid in the container is called gelling time). The reason is that KH-550 is an amino silicon Anhui coupling agent, and ammonia gas is released after hydrolysis. Ammonia is an alkaline catalyst, which makes the gelation time of sol over fast polycondensation and okh-560 as coupling agent shorter than that of KH-570. The reason needs further study.






3.3 effect of sol concentration on coating and coating performance






The sol concentration will directly affect the thickness of the coating, and then affect the scratch resistance of the coating. Generally, the thicker the coating, the better the wear resistance. Table 3 shows the effect of sol concentration on coating performance. It can be seen from the table that the hardness of the coating increases with the increase of sol concentration, but the storage time shortens. 3 with the increase of sol concentration, the thickness of the coating increases, so the hardness is improved. However, the higher the sol concentration, the better.