Coating water-borne system

To further reduce the emission of solvents from coatings, water-borne two-component coatings cross-linked with isocyanates are being developed. The challenge in formulating these systems is the selection of a catalyst that is hydrolytically stable and catalyzes only the hydroxyl reaction and not the water reaction. Di-n-butyltin carboxylates i or phenoxides hydrolyze to the oxide in water. Di-n-butyltin bis(2,3-dihydroxypropylmercaptide) is reported to be stable in water and has been used in two-component water-borne coatings. ... 

Of the various surface active chemistries currently available, this paper will mainly concentrate on a class of materials called Silicone Polyethers. This family of copolymers is used to provide multifunctional benefits in water borne systems. The main uses of silicone polyethers in inks and coatings include de-foaming, de-aerating, improved substrate wetting, levelling and enhanced slip properties (1,2). The three most common molecular structures for silicone surfactants are rake type copolymers, ABA copolymers and trisiloxane surfactants. These are illustrated in Figs 1,2 and 3 respectively and the performance of these structures will be described in two types of coatings ... 

Waterborne coatings. These are based on two-component epoxy-polyamine/polyamidoamine or epoxy-acrylic latex hybrids. One limitation of the water-borne systems is their poor cure in high humidity conditions. They have made some penetration in industrial maintenance coatings and are expected to grow more significantly in the future. 

Silane coupling agents may also be directly used as coatings for a variety of applications (10,13,14). Coupling agents in coatings formulations can be used in either solvent- or water-borne systems, such as clear coats for automotive applications (13,15). Formulations can also be used to impart scratch and abrasion resistance to softer materials such as polycarbonate and poly(methyl methacrylate) (PMMA) (14). Applications of this type allow the use of materials whose bulk properties are desirable because the surface properties can be fine-tuned. 

One adhesives area which is expected to move heavily towards water-borne systems is the contact adhesives segment. Both waterborne neoprene and acrylic based systems are expected to contribute to this growth. A contact adhesive is a material which, when coated and allowed to partially dry on two surfaces, may have little residual surface tack (to the touch) but forms a strong joint when the two coated substrates are brought together under low to moderate pressure. 

Even though, water-borne coatings have been the most popular approach to VOC reduction and there has been a substantial reduction of solvents on going from solvent-bome systems to water-borne systems, the trend now is to eliminate solvents... 

Fig. 4. Dose response for blood glucose measurement using a dry chemistry system having a water-borne, tough coating film. The numbers represent...

Besides the solvent composition, the vehicle system is responsible for various drying deficiencies associated with water-borne coatings, such as slow initial dry time, loss of dry, poor through drying, and hardness (see Coatings). 

The vehicle system of water-borne coatings can be divided into two categories water-emulsifiable vehicles and water-soluble vehicles. 

Water-based inks, 14 326 Water-based muds, 9 3-5 Water-based writing inks, 14 328 Water-borne adhesives, 25 475 Waterborne alkyds, 2 156-158 Waterborne automotive coatings, 10 448 Waterborne can coating system, 10 445-446... 

Water-borne coating systems have been the focus of significant research in recent years, which continues to be driven by tighter environmental regulations. Aqueous based dispersions of polymeric lattices provide a viable alternative to organic... 

Visconti M, Cattaneo M. (2000) A highly efficient photoinitiator for water-borne UV-curable systems. Prog Org Coatings 40 243-251. 

The complete elimination of heavy metals and other hazardous compounds from the coating systems was the main objective of SAIE. Chromated spray primers with hazardous chromate components do not fit such an objective. Therefore, two kinds of nonchromated and water-borne spray primers, Spraylat EWAE118 (D) and Dexter lO-PW-22-2 (X), were selected to produce chromate-free plasma coating systems for corrosion protection of A1 alloys. 

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