Thixotropes, coatings

Uses Adhesion promoter in surf, coatings thixotrope, crosslinking agent for emulsion... 

Improves runnability, particularly well-suited for roll coating (thixotropic coating colors can be prepared)... 

The hand lay-up or spray-up process, used universally for the production of laminar composites incorporating glass fiber reinforcement, is most efficient for the manufacture of large parts, such as boats, bathtubs, tanks, architectural shapes, and recreational accessories. Resins intended for spray-up processes are usually modified with thixotropic additives, such as fumed siHca (1%), to reduce the risk of drainage when appHed over large vertical mold surfaces. Molds are also made from ERP for short-mn products usually surfaced with a tooling gel coat to provide consistent surface quaHty and appearance. 

The alkoxy titanate compounds formed by reaction of one mole of tetraalkyl titanate with one mole of a dialkanolamine are excellent esterification catalysts for the manufacture of phthalate-based plasticizers (112). If a 1 1 molar mixture of alkanolamine and water is used ia place of the alkanolamine, oligomeric titanate complexes are formed, which have high catalyst activity and can be used as thixotropic additives to paints and other aqueous coating formulations (113). 

Thermoplastic polyamides are used in coatings to modify alkyd resins (qv) in thixotropic systems (238) and to plasticize nitroceUulose lacquers (239). DETA-taH oil fatty acid-based polyamides are suggested for use as corrosion inhibitors in alkyd paints (240). Printing inks for fiexo-gravure appHcation on certain paper, film and foil webs rely on EDA- and PDA-based polyamides for their specific performance (241). 

The most important coating appHcation for the nonreactive polyamide resins is in producing thixotropy. Typical coating resins such as alkyds, modified alkyds, natural and synthetic ester oils, varnishes, and natural vegetable oils can be made thixotropic by the addition of dimer acid-based polyamide resins (see Alkyd resins). Specialty high performance coating appHcations often requite the properties imparted by dimer acid components. 

As stated above, high performance coatings based on epoxies, vinyls or chlorinated rubbers are used almost exclusively on all large ships. A general development in these materials has been the introduction of highly thixotropic types that can be airless sprayed at wet film thicknesses of 300 im or more, that do not run or sag on vertical surfaces. This enables the requisite film thickness to be applied in fewer coats, saving time and reducing application costs. 

Thixotropic suspensions are generally required for static coating due to the long column preparation time. 

Several conditions are necessary for satisfactory surface coatings, e.g., nondrip applications. There is a balance between the ease of use and sagging of the paint during and after administration. Thixotropic additives, e.g., organo-montmorillonite clays are added. These form 3-dimensional networks, which are easily broken down by shear. 

When suspended colloidal particles form a network through the liquid, viscosity is increased. For silica gels the thickening and thixotropic effects are used in a large number of applications. The silica is mixed with paints, coatings, inks, pharmaceutical and cosmetics with this purpose.34... 

Calcium carbonate filler is a particulate filler that is generally employed to impart thixotropic properties and as an extender. However, improvements in physical properties such as tensile strength, tear, and elongation have been noticed as a function of surface area. This effect is noted more so with the coated CaC03 products. 

Carr, J. B., Attapulgite-Based Thixotropes Offer Performance and Flexibility, American Paint and Coatings Journal, November 1997. 

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