Water-borne systems

For viscosity or sag control. When the rubber base adhesive is applied on a vertical surface, addition of a filler prevents the adhesive from running down the wall. In solvent-borne formulations, fumed silica can be used as anti-sag filler. In water-borne systems, clays impart yield stress and excellent sag control. 

ATRP can also be carried out in water under homogeneous [208] or under bi-phasic conditions [209-211]. Block and statistical copolymers have also been prepared in water-borne systems. Matyjaszewski et al. demonstrated that a copolymerization of MMA with either BA or nBMA proceeded in a controlled fashion, resulting in copolymers with Mn=26,850 (Mw/Mn=1.22) or Mn=33,550 (Mw/Mn=1.25), respectively [121]. A pnBA macroinitiator prepared in a bulk... 

ATRP polymerization (Mn=5750) was chain extended with St to yield a block copolymer with Mn=21,400 and an Mw/Mn=1.15, after 24 h and 78% monomer conversion, as shown in Fig. 29 [121], Although the authors showed that both statistical and block copolymers could be prepared in the water-borne system, the latex stability was often low and phase separation was observed. Success in these polymerizations depends strongly on the nature of the additives present (i. e., surfactant, macroinitiator, etc.) [121,212]. 

Many approaches have been described in the patent literature. They include water-borne systems, powder, high solids, radiation curable, electrocoat, etc. The types of resin... 

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 ... 

The Clean Air Act demands the elimination of organic solvents use, hence a number of plasticisers and solvents (such as methylene dichloride (MEK), toluene, xylene) are classified as hazardous, which led to development of new, environment compliant systems to develop, such as water borne systems, or use of rapidly curable/dryable oligomers (i.e., printing inks use oligomeric bis acrylates, polyester acrylates and polyurethane acrylates, which can be crosslinked quickly by UV light with the aid of certain sensitisers). 

Properties and Chemical Structure of Fluoroalkylalkoxysilanes and Corresponding Water-Borne Systems... 

A number of water soluble thioxanthone derivatives were prepared specially for water borne systems. They can be illustrated as follows ... 

Outstanding properties high temperature and extraction resistance, miscible with all common solvents but also easily incorporated into water borne systems... 

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. 

Gaynor, S. G., Qiu, J., and Matyjaszewski, K. (1998). ControUed/ living radical polymerization applied to water-borne systems. Macromolecules, 3/(17) 5951-5954. 

Toxicity, flammability, and materials shortages associated with organic solvents have resulted in the development of several new water-borne adhesive systems. Many of the previously effective adhesive formulations are not readily converted to water-borne analogs. Many of the previously understood solution property-performance correlations remain valid in water-borne systems some do not. In this work an effort has been made to improve our understanding of the adhesive mechanisms and property-performance correlations in solvent and water-borne contact adhesives. These adhesive systems include phenolic/neoprene and phenolic/acrylic compositions. Some of the physical properties of the individual components and of the phenolic/elastomer blends have been related to contact adhesive performance. 

Toxicity, flammability, and material shortages associated with organic solvents have resulted in a trend towards water-borne adhesive systems. The transition from solvent to water-borne systems involves more than simple reformulation additional variables are encountered and a properly designed system should control each of these variables to optimize adhesive performance. 

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. 

How important is the particulate nature of the phenoic dispersion to its role of enhancing green strength in water-borne systems Is it simply serving as an inert filler to enhance wet strength or... 

As in conventional solvent systems, phenolics can serve as effective tackifiers in properly designed water-borne systems. Most notable is the fact that water, as well as solvents, can serve to plasticize the phenolic. Also care should be taken to insure that the phenolic is the proper molecular weight, that the components are at least partially compatible, that the phenolic does not form the bulk of the continuous phase, that the surfactants employed do not form weak boundary layers at substrates, and that elevated temperature tests approximate use conditions. 

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