Paints alkyd resin blending

Vinyl resins ie, copolymers of vinyl chloride and vinyl acetate which contain hydroxyl groups from the partial hydrolysis of vinyl acetate and/or carboxyl groups, eg, from copolymerized maleic anhydride, may be formulated with alkyd resins to improve their appHcation properties and adhesion. The blends are primarily used in making marine top-coat paints. 

Silicone resins with high phenyl contents may be used with medium or short oil alkyds as blends in air-dried or baked coatings to improve heat or weather resistance the alkyd component contributes to adhesion and flexibiUty. AppHcations include insulation varnishes, heat-resistant paints, and marine coatings. 

Both paints and adhesives are commonly formulated as polymer blends or grafts. In fact, some compositions resemble semi-IPN s or AB crosslinked copolymers (Section 8.7). For example, epoxy adhesive resins are often cured with polyamides (Bikerman, 1968). The product is tougher than materials cured with low-molecular-weight amines, possibly because of a separate amide phase in this AB crosslinked copolymer. A more complex molecular architecture is exhibited by the alkyd resins common in oil-based paints (Martens, 1968, Chapters 3 and 4). The major component is a polyester, which often forms a network structure on drying. The polyester component is reacted with various drying oils, such as linseed oil or tung oil (Martens, 1968, Chapters 3 and 4). These oils form an ester link to the polyester structures and also polymerize through their multiple double bonds. Latex paints always contain thickeners, such as cellulosics, poly(acrylic acid), casein. 

Low grades are used for industrial purposes in soap (after hydrogenation), in blends with linseed etc. in paints and varnishes and in alkyd resins. Paints based solely on sunflower oil have a good resistance to yellowing because of the low linolenic acid content. The use of the oil as a diesel fuel is also being explored (Zimmerman, 1981). 

From the time of these original oil paints to the present, there have been several phases firstly, the simple oils were replaced by heat-thickened oils. Natural resins, followed by synthetic resins, were then blended into the oils, and, finally, the oils were chemically incorporated into oil-modified synthetic resins, notably the alkyd resins. 

Newer types of high-performance paints used on ship exteriors include those based on epoxy resins, polyurethane resins, vinyl resins (also vinyl/ alkyd or vinyl/acrylic blends) or chlorinated rubber. Epoxies and polyurethanes are chemically-curing types and present curing problems at low temperatures, whilst the overcoating intervals are critical for best adhesion... 

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