The role of desculation agent in water-based coatings and screening methods (2)

2.3 desiccant evaluation method
2.3.1 stirring test the desiccant to be tested into the blank sample, stirring at 2,000 r/min speed 10 min, placed 24 h.50 g sample, stir 3 min (3,000 r/min, 3 cm dispersion tray) and immediately pour the 45 g sample into the drum to record the volume reading in the drum. The smaller the volume, the stronger the deblistering capacity.2.3.2 Dumping Testpours the samples from the cartridge on a tilted polyester film (polyester film at an inclination of 25 degrees vertically). The defocing efficiency is evaluated according to the density of foam distribution on dry film. Use 5 levels to describe de-foaming efficiency. Level 5 represents a high deblistering effect, and level 1 represents a low deblistering effect.2.3.3 compatible and shrink hole check apply a 50 m wet film on the glass plate, after applying the film dry film to check whether the appearance of the coating film is clear and transparent, the plate surface is a shrink hole.2.3.4 glossis sprayed on a board with a closed primer, and the gloss of the coating film is tested after drying, using a Sheen glosser.2.3.5 Brushing Test Brushing on a board with a closed primer, after the coating is dry, observe the surface state of the coating film, check whether there are bubbles, shrink holes, turbidity and other problems in the coating film. Use 5 levels to describe de-foaming efficiency. Level 5 is in good condition, and Level 1 is in the worst state.2.3.6 Storage Stabilitywill be added to the desiccant coating in a 50 degrees C oven placed 14 d, and then repeat the above test steps and record the results.2.4 Test Results (see Table 3, Table 4) 3 Results and Discussion 3.1 Selection of defoaming agents through test resultsTherefore, we recommend using Tego Foamex843 (0.4%, mass score), Tego Airex 902W (0.4%, mass score) to solve the de bubble problem. In water-based coatings, sometimes a single debobbling agent can not achieve satisfactory results, through the combination of desobbists and de-foaming agents, generally can achieve satisfactory results.3.2 Deboulant efficiency and compatible in the selection can not blindly choose the most blistering ability of desiccant, deboulant selection must take into account deblistering efficiency and debogging agent compatible with the system, the latter is more important. If the deboulant is too poorly compatible in the system, it will lead to the appearance of surface defects such as shrink hole turbidity, and if the compatible is too good, the de-foaming effect may be reduced, so the opt-out deboulant must find the best balance between de-foaming efficiency and compatible.3.3 The importance of the storage test in the selection of desiccants In the selection of desticants, it is recommended to do storage tests, because desiccants in the storage process, due to interaction with surfactants, over time, it is possible to reduce deblistering efficiency, so it is recommended that after doing a good initial screening test, the sample storage, by evaluating the ability and compatible performance after storage, and ultimately determine the choice of de bubble agent.
limitations of the 3.4 laboratory simulation deblistering test . For water-based coatings, the choice of desiccant is complex, through the laboratory can only make preliminary screening results, with preliminary screening results, must be tested in practice, through the construction of the test to final determine the formula.4 Conclusion The application of defrosting agent in water-based coatings is essential, when we understand the cause of bubbles in water-based coatings, the type of desobbists and the action of the working conditions, the use of the correct test method to evaluate and screen out the appropriate desolation agent or desobbists combination is an important work to solve the problem of water-based paint foam..