| Two-component ambient-cured waterborne epoxy coatings system is one perspective approach to replace solvent borne epoxy/polyamide, which attracts so much attention due to their broaden popularities in a variety coatings.A review of historical development of waterborne epoxy system has shown two fundamentally different technologies have involved, each offering distinctive benefits and limitations .The waterborne technologies fall into two categories. Based on the physical state of epoxy resin employed, namely type I system and type II system. Type I system is based on liquid epoxy resins. Typically, the waterborne curing agents is used to emulsify the liquid epoxy as soon as curing agents and epoxy resins are mixed together; Type II system water borne epoxy system are based on a higher molecular weight solid epoxy resins that are pre-dispersed by special equipment in water and co-solvents. Curing agent must migrate from the aqueous phase into the dispersed epoxy particles for reaction to occur. In this paper the emphasis are laid on some studies, such as synthesis of the reactive emulsifier, procedure of solid epoxy resin emulsification and synthesis of self-emulsifying curing agents.As for type II system, a high-efficiency, polymerized and reactive emulsifier has been developed, aimed to avoiding conventional surfactants free from film by water scouring owing to reaction between epoxide group and amine curative.In the presence of some Lewis acid (as a catalyst), EPON1001 and PEG (with various molecular weight) formed block copolymers. The reactive result has been characterized by FTIR and other methods. The parameters of process, including concentrations of catalyst, type of PEG, reaction temperature, and reaction times have been determined. Especially, the concentration of catalyst's influence on the resultant has been discussed hi detail. Conditions of emulsification process including emulsification temperature ,type of emulsifier(resultant of the various molar ratio of OH group to epoxy group and reaction between various molecular weight PEG with EPON1001) emulsification method, minimum concentration of emulsifier, have been determined, advantageously, ratio:1:1 ,temperature:70-80 C, phase inversion emulsification process, emulsifier concentration: 10wt%. Reasonable explanationsabout those all have been given respectively. Average size of epoxy emulsion by phase inversion emulsification is 1.08 u m without settings within 6 months.Regarding Type II system, a curing agent with acceptable film properties has been developed,-which overcomes some limitations in stereotype Type I system film, such as too high hardness, low flexibility and low impact resistance, as a result of introducing of a multi-branch mono epoxide compound and long chain aliphatic alcohol mono glycidyl ether which posse structural flexibilities.Adduct of epoxy/amine (DETA) with chemical construe ABA has been synthesized, and characterized by FITR and other methods. End-capped agents and degree of salting has been determined. Results show that Long-chain aliphatic alcohol mono glycidyl ether and branched mono epoxide compound perform well with ratio of 1:1,degree of salting 25%. Dry film performance studies on self-emulsifying curative reaction with unmodified liquid epoxy and modified one by reactive thinner independently have been carried out, as well as ratio of epoxy equivalent to amine hydrogen equivalent about two systems. It has confirmed that reactive dilute 's addition to liquid epoxy resin facilitate the film properties owing to its particular film formation. Studies on Cross linking behavior between various self-emulsifying curing agents various epoxy resins has been discussed by thermo analysis and measurement of emulsion particle size. A conclusion could be drawn that a good curing agent with low Tg, proper reactivity and good emulsification performance is the key to good film performance.A glossy coatings formulation based on TiO2 has been given, including additives and testing properties. |
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