Emulsion polymers coatings applications

Emulsion polymerization also has the advantages of good heat transfer and low viscosity, which follow from the presence of the aqueous phase. The resulting aqueous dispersion of polymer is called a latex. The polymer can be subsequently separated from the aqueous portion of the latex or the latter can be used directly in eventual appUcations. For example, in coatings applications-such as paints, paper coatings, floor pohshes-soft polymer particles coalesce into a continuous film with the evaporation of water after the latex has been applied to the substrate. 

Latex IPNs. Latex IPNs are the third type of IPNs and are manufactured according to the general schematic illustrated in Figure 3. Latex IPN synthesis involves the initial synthesis of a crosslinked seed polymer, usually in the form of an aqueous latex. The seed latex is then swollen with a second monomer/crosslinker/initiator system which is then polymerized "in situ" to form an aqueous IPN emulsion. Materials of this type are best suited to coating applications as illustrated by the development of "Silent Paint" by Sperling et al ( ). However, latex IPNs are limited to water emulsifiable monomer/polymer systems, most of which have fairly low service temperatures, less than 150 C. 

The movement of the pharmaceutical industry away from volatile solvents for coating applications coupled with advancements in coating equipment design led to an increase in the popularity of latex and pseudolatex coating systems. Latexes and pseudolatexes are both colloidal dispersions of polymer droplets in a continuous aqueous phase, the difference between them being that latex systems are formed by emulsion polymerization... 

The utility of the bis cyclic ureas for curing of coatings was demonstrated by dispersing them in a functional acrylic polymer formulated for powder coating application, or by using them as additive in solvent based coatings or in aqueous polymer emulsions for electrocoating. 

Solubilizable Dispersions (19). The chemistry of solubilizable acrylic dispersions is a hybrid of emulsion and water-reducible technology. These polymers are synthesized by emulsion techniques but contain acidic or basic functionality that renders them water soluble upon neutralization with an appropriate titrant. For example, if the solubilizing functionality is acidic, the polymer will behave like an emulsion below a certain critical pH range, like a highly swollen emulsion within the critical pH range, and like a true water-soluble polymer at sufficiently high pH values. Such polymers offer a favorable balance of properties for many coating applications. 

Liu et al. also studied LIPN systems for damping control in coating applications [Liu et al, 1995]. A polystyrene (PS)/polyacrylate (PAcr) latex IPN was synthesized in a two-stage emulsion polymerization. Crosslinked PS was synthesized first as the seed polymer by a semi-continuous process,... 

Emulsion polymers have been used in a broad range of applications because of their environment-friendly nature and the versatility of the process for adjusting both macromolecular and colloidal properties of the latex. Out of the worldwide demand of emulsion polymers, 23% is used for surface sizing and coating of paper and paper board, 20% for paints and coatings, 25% for adhesives and sealants, and 9% for carpet backing [234], References 234 and 235 and several chapters of the book edited by Lovell and El-Aasser are devoted to the major industrial uses of emulsion polymerization and polymer latexes. 

A majority of the acrylic emulsion polymers used in textile and non-woven applications are crosslinked or cured after film formation to provide wet stroigth, solvent resistance and durability to laundering and dry cleaning. As with architectural coatings binders, the principal monomers used are BA, EA and MMA,... 

The mechanical properties of polymers can be studied in a large variety of ways [189]. Some examples of the mechanical properties of emulsion polymers are described in the next section. Mechanical testing of films with the aim of obtaining information useful in coating applications has been described by HiU [190]. 

---