Analysis of Advantages and Disadvantages of Modification Methods of Waterborne Epoxy Coatings

Water-based epoxy resin with its outstanding performance advantages, so that the preparation of water-based epoxy resin coatings also have excellent performance, so that in the large family of aquatic products more and more important, experts believe that water-based epoxy resin in environmental protection today, the prospects are very open. 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
the
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hydro-water-based epoxy form resin can form three water dispersion forms through different water-based ways:
(1) water solubility;
Epoxy resin itself is a thermoplastic wire structure, after heat solid state 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:
a) 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.
b) particle size: When the particle size is small, water-based epoxy resin and water-based epoxy curing agent dispersed phase particles can penetrate each other more fully into the core to achieve a more complete curing degree.
c) hydro-hydro-oil-pro-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 the resin phase and curing agent.
d) dispersion uniformity: in the state of multi-phase separation, only through a certain mechanical stirring action, the resin phase and curing agent can be evenly distributed in the water phase; (Epoxy is very important in the application of mixing and mixing well) (Some friends in the process of using oily epoxy think that as long as simple stirring or even do not stir can also form a film, in fact, there is a big mistake, because the use of oily epoxy is dissolved by solid epoxy such as 75% E-20, even if not reinforced agent, solvent volatile can be formed Very hard dry film state, but this dry film is not curing agent cross-curing, after heat into liquid, dry film has no performance to speak of





Emulsification refers to the direct emulsification of epoxy resins, self-emulsification without emulsification with emulsion agents or emulsification of water-based epoxy curing agents, and the salinization method is to transform epoxy resins into acid-rich or alkali-rich resins, and then neutralize them with a small molecular mass of alkali or acid.
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.
amide modified
ide itself has a certain water solubility or water dispersion, without the use of solvents or emulsifying agents to obtain a certain range of water dilution, which 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. With single fatty acid modified amamine polyamine curing agent, and epoxy resin compatibness is not too good, easy to occur phase separation and surface defects such as oil sealoids and pits on the surface of the coating film, and insufficient curing results in poor chemical resistance and moisture resistance of the coating film.
Polyamide modified
the use of dipolycic acid and polyamine shrink to prepare water-based polyamide curing agent, so that the modified can improve the compatible with epoxy resin, coating surface 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 due to the presence of unsaturated double bonds in dipolyacid acid, and easily by oxygen oxidation in the air lead to darkening of the color of the curing agent, not suitable as a color requirements of higher water-based epoxy floor coating curing agent. This method of change has certain limitations, of course, this does not hide its application advantages.
doamine polyoxyoxygenation
due to the use of alamide polyamine and polyamide water-based curing agent curing film more or less defective, and modified film performance has not been significantly improved, so the use of water-based epoxy curing agent for multiple The amine-epoxy supplement, using epoxy resin and polyamine reaction, introduces epoxy resin molecular chain in the polyamine molecular chain, makes the synthetic curing agent have the molecular structure of pro-epoxy resin, and reduces the content of the beetamine group in the curing agent molecule can significantly reduce the activity of the 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 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.