Because the thickness of the coating is too large and the cohesion of the coating increases when the rubber concentration is too high, the coating will crack and the kink force is poor. In general, the concentration of sol should not exceed 20%, but it should not be too low, the concentration is too low, the resulting film is too thin, and the film presents five colors. The better sol concentration should be controlled between 12% and 14%.






The shorter storage time is due to the higher concentration of sol, and the greater possibility of condensation reaction between Si oh and Si oh and Si or.






3.4 effect of heat treatment temperature on coating performance






Fig. 2 and Fig. 3 show the effect of heat treatment temperature on the hardness and wear resistance of the coating, respectively.






It can be seen from Fig. 2 and Fig. 3 that: before 120 ℃, with the increase of heat treatment temperature, the hardness and wear resistance of the film are obviously improved; when the heat treatment temperature reaches 120 ℃, the hardness of the film reaches the maximum value, which is sh; when the temperature reaches 120 ℃, the wear resistance reaches the maximum value. The land boundary load is 30g. However, too high curing temperature does not help to improve the hardness of the coating, but will reduce the scratch resistance of the coating. The main reason is that the cohesive force in the coating increases due to the high curing temperature, which leads to the decrease of the sweet bonding force between the coating and the substrate. As a result, the coating is easy to fall off from the surface of the substrate when subjected to friction, and the scratch resistance is reduced.






No matter what kind of plastic, its heat treatment temperature should not exceed its glass transition temperature, generally lower than the glass transition temperature of IO ℃ or above, otherwise the product deformation will seriously affect its surface quality. The glass transition temperature of epoxy resin used in this test is 140 ℃, so the heat treatment temperature of this test is 120 ℃.