Acrylic coating polymers film properties

General. The solution and film properties of an acrylic coatings polymer are determined by (1) the molecular weight, (2) the nature of the polymer solution, and (3) the composition of the polymer backbone. 

C) It is well-known that the presence of certain types of functionality in the ester side chain imparts specific characteristic film properties to the acrylic coating (7). Some of these characteristics are summarized in Table II. By knowing the end use requirements of flexibility, adhesion, hardness, etc., the acrylic coatings polymer chemist can often tailor-make a polymer to fit the defined needs of the application. 

Nimkulrat S. Suchiva K, Phinyocheep P, Puttipipatkhachom S. Influence of selected surfactants on the tackiness of acrylic polymer films. Int J Pharm 2004 287(1-2) 27-37. Okhamafe AO, York P. Effect of Solids polymer interactions on the properties of some aqueous-based tablet film coating formulations 2. Mechanical characteristics. Int J Pharm 1984 22(2-3) 273-8I. 

The understanding of the relation between the macroscopic film properties of an acrylic coating and the polymer composition has been advanced significantly by the successful application and interpretation of two physical models (1) the glass transition temperature, Tg (2) the solubility parameter, 6. 

The results of investigations of the effect of method of hybrid dispersion synthesis (la, lb, 2 or 3 - see Section 3.2) on the properties of dispersions as well as of films and coatings made from them are presented in Tables 6.9 to 6.11 (dispersions prepared using water-soluble initiator) and in Tables 6.12 to 6.14 (dispersions prepared using redox initiating system). In all dispersions the chemical structure of the polyurethane-urea and acrylic/styrene polymer component was the same (see relevant tables in Section 6.5.2). All the dispersions contained a similar low level (2-3.6%) of NMP. 

One of the most important groups of film forming latexes used in waterbourne coatings is the group of acrylic resins. These are for the most part, the polymers obtained from acrylate and methyl acrylate esters of lower alcohols, of which methanol and butanol have the widest application. Those based on MMA and butyl acrylate (BA) yield copolymers with good film properties [81]. 

Maleate esters such as dimethyl maleate, diethyl maleate and dibutyl maleate are extensively used in the production of latex emulsion polymers, thermoplastic and thermosetting plastics. Dimethyl maleate has found use in applications where improvement in hardness and toughness of polymer films are desired. This includes, in particular, the improvement of anti-blocking properties of copolymers of vinyl acetate with dimethyl maleate. It is also used as an internal modifier to increase the glass transition temperature of styrene or vinyl chloride polymer. The intermediate in esterification of maleic acid with methanol, monomethyl maleate provides plastsizing effect, as well as promotion of improved polymer adhesion due to the carboxylic group. It can be copolymerized with a variety of vinyl and acrylic monomers to provide coatings with improved stiffness and adhesion and reduced tackiness or tendency to block. Monoesters of maleates are used to provide carboxylic acid functionality in emulsions and water-soluble polymers. 

A combination of methacrylates and acrylates is used on occasion to achieve needed film properties. While poly(methyl methacrylate) is commonly used for film strength and hardness, poly(methyl acrylate) will improve film flexibility. A plasticizing monomer, such as ethyl acrylate or ethylhexyl acrylate is therefore sometimes added with the methyl methacrylate monomer by the polymer manufacturer in an addition-polymerization process to produce a copolymer for use in coating formulations. The softer and more flexible polymer facilitates latex film formation. 

The basic chemistry of emulsion-based acrylics is the same as their solution-based counterparts, in the sense that they are both combinations of hard and soft acrylic monomers, the ratios of which will dictate the final film properties. If a hard mar resistant coating with some alcohol and chemical resistance is desired, emulsions polymers with a Tg of 80°C will be required, unless the coating is crosslinked. 

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