Analyze the advantages and disadvantages of water-based epoxy coating modification methods

The advantages of water-based coatings are obvious compared to solvent-based coatings. Such as low VOC, small odor, safe use, can be washed and so on. Water-based epoxy form resins can form three water dispersion forms through different water-based ; Epoxy resin itself is a thermoplastic wire structure, after heat solidity into liquid, high viscosity into low viscosity, only with curing agents to use only practical value (pure single-group water-based epoxy system also needs to be added latent curing agent). Therefore, the water-based epoxy system should contain water-based epoxy resin and water-based epoxy curing agent, similarly, they can form three water dispersion forms through different water-based ways.
The degree of curing of water-based epoxy depends on the following four factors:
1) compatible: the better the compatible between water-based epoxy resin and water-based epoxy curing agent, the more conducive to the internal diffusion of curing agent particles and epoxy particles, is conducive to the curing reaction;
2) particle size: when the particle size is small, the dispersed phase particles of water-based epoxy resin and water-based epoxy curing agent can penetrate each other more fully into the core, thus reaching a more complete curing degree;
3) Hydro-hydro-oil balance value: water-based epoxy resin and water-based epoxy curing agent hydro-hydro-oil balance value is close, in the water phase to achieve consistent coexistence and stability, if the difference is large, hydro-hydrogenic groups will gradually gather in the water phase, resulting in the separation of resin phase and curing agent;
4) Dispersion uniformity: in the state of multi-phase separation, only through a certain mechanical stirring effect, the resin phase and curing agent can be evenly distributed in the water phase; (Epoxy is very important to mix well in the application) (Some friends in the process of using oily epoxy think that as long as simple stirring or even not stirring can be filmed, in fact, there is a big mistake, because the oily epoxy used is dissolved by solid epoxy such as 75% E-20, even if not reinforced Agent, solvent evaporation can form a very hard dry film state, but this dry film is not cured by cross-curing agent, after heat into liquid, dry film has no performance to speak of
Emulsification refers to the direct emulsification of epoxy resin, self-emulsification or water-based epoxy curing agent emulsification without emulsification of emulsifying emulsion, and the saline method is to transform epoxy resin into a resin rich in acid or alkali, and then neutralize it with a small molecular mass of alkali or acid. Water-based epoxy curing agent emulsified epoxy resin is the most important water-based technology, which can overcome the shortcomings of other water-based methods. Most commonly used water-based epoxy curing agents are polyamines or their modified products, in which the modified products mainly use the active hydrogen on the amine base in its molecules and epoxy-based reactions in the epoxy resin molecules to make changes. There are three commonly used modified methods of polyamine, all of which use non-polar groups in the polyamine molecular chain, so that the modified polyamine curing agent has a two-parent structure to improve compatible with epoxy resin.
first of all, alamide polyamine modified. The polyamine of alamide itself has a certain water solubility or water dispersion, without the use of solvent or emulsifying agent to obtain a certain range of water dilution, so that it can be used as a water-based epoxy resin curing agent. And the role of polyamines with surfactants, low molecular quality liquid epoxy resin does not need to be pre-emulsified, and by aamide polyamine before construction mixed emulsification, with alamide polyamine emulsified epoxy resin with a water-based epoxy system has good construction performance, long application period and other advantages. The compatible with epoxy resin with single fatty acid modified alamide multiamine curing agent is not too good, easy to separate and surface defects such as oil sealoids and pits appear on the surface of the coating film, and insufficient curing results in poor chemical resistance and moisture resistance of the coating film. The second is the change of polyamide. The water-based polyamide curing agent is prepared by shrinking dipolyacids and polyamines, so that the modified sex can improve the compatible with epoxy resin, and the surface of the coating film will not appear due to incompatible surface defects; And with polyamide cured coating film flexibility is poor, impact performance is poor, the coating film is brittle. Water-based polyamide curing agent is not suitable as a curing agent for water-based epoxy floor coating with higher color requirements due to the presence of unsaturated double bonds in dipolyacid acid in synthesis, and is easily caused by oxygen oxidation in the air. This method of change has certain limitations, of course, this does not hide its application advantages.
method is polyamine epoxy plus. Because the coating film cured with aamide polyamine and polyamide water-based curing agent is more or less defective, and the modified coating film performance has not been significantly improved, so the water-based epoxy curing agent used abroad is polyamine-epoxy supplement, Using epoxy resin and polyamine reaction, epoxy resin molecular chain is introduced in the polyamine molecular chain, so that the synthetic curing agent has the molecular structure of pro-epoxy resin, and reducing the content of beamine group in curing agent molecules can significantly reduce the activity of curing agent. The application period of emulsified epoxy system emulsified with this type of water-based epoxy curing agent is extended, and the problem of coating film brittleness is improved by adding polyoxidizing alkyl polyamine. The expert also said that if the water-based epoxy curing agent is to have emulsified epoxy resin function, it needs to be obtained by attracting human oxide alkyl chain segments in the curing agent molecular chain, or ion-based groups.
water-based epoxy system has more choice combinations (theoretically with 9 morphological combinations), but also increases the difficulty of selection. At the same time, in the practical application process, by adding a large number of pigments, additives, etc., improve the application performance of water-based epoxy system at the same time also cover up the water-based epoxy system deficiencies and even serious defects, which will increase more uncertainty and complexity. Discarding the simple, respectively, pay attention to the water-based epoxy resin form and water-based epoxy curing agent form at the same time, by controlling the nature of water-based epoxy and water-based epoxy assessment to achieve a faster and better choice of water-based epoxy system, for your high-rise to lay a solid foundation.