Pigments reactive resin systems

There are two general classes of photoinitiators (1) those that undergo direct photofragmentation on exposure to uv or visible light irradiation and produce active free radical intermediates and (2) those that undergo electron transfer followed by proton transfer to form a free radical species. The choice of photoinitiator is determined by the radiation source, the film thickness, the pigmentation, and the types of base resin employed. Examples of typical photoinitiator systems used to cure reactive resins are shown in Table 14.2. Benzophenone is perhaps one of the most common photoinitiators. 

In order to replace lead and chromate pigments, much attention has been focused upon zinc phosphate. Today, zinc phosphate is one of the most commonly used phosphate-containing anticorrosive pigments. The formulation versatility, due to the extremely lower solubility compared with chromate and other pigments, and therefore the lower reactivity, has led to its economic importance in the market Zinc phosphate can be used in a wide variety of resin systems [5.53, 5.55]. 

Epoxy resins are normally used in what is called an epoxy-resin system. This system consists of the epoxy resin and a hardener, and reactive diluent or other additives, such as fillers, modifiers, pigments and reinforcements. 

Synonyms include Furyl Carbinol, 2-Hydroxy Methyl Furan, 2-Furan Methanol, Furfuryl alcohol resin. Furan resin, FA resin, Poly(furfuryl alcohol). Prepolymers of FA. It is a raw material for organic synthesis, producing levulic acid, resin of various furane kinds in different properties, furfuryl alcohol urea formal resin and phenolic resin. It is a fine solvent for furane resin and oil varnish and pigment as well as used in rocket fuel. It is also used in the production of synthetic fibers, rubber, agricultural chemicals and foundry products. Furfuryl alcohol resins are derivatives of agricultural waste products and complex polymers that are formed in a condensation reaction that occurs when the furfuryl alcohol is acidified. The resins have low viscosity with an odor of furfuryl alcohol. The resin systems are highly reactive and can be catalyzed using a variety of active and latent acidic catalysts. When thermoset, the resins produce polymers that are heat resistant and extremely corrosion resistant to acids, bases and solvents. 

Unsaturated polyester resins are mainly made by condensing a dibasic acid (1,2-propanediol) with an anhydride (maleic or phthalic anhydrides), by forming ester linkages between the dibasic acid (or their anhydrides) and glycols. Then a reactive monomer (mostly styrene or vinyl toluene, MMA or diallyl phthalate) is used to crosslink the system when needed. Unsaturated denotes the uncompleted chemical activity (double bond) in the original structure, which are used for crosslinking afterwards. In this context, an excess of styrene as the crosslinker (10 to 50 %) is usually added to have it ready in the system, as well as to reduce the viscosity. There are also certain accelerators used (such as, cobalt naphthenate or tertiary amines like dimethyl aniline) to facilitate the cure at ambient temperatures. In addition, there may be pigments, fillers, various inhibitors, accelerators, stabilisers and flame retardants, added to the system. Polymerisation is activated whenever a catalyst (i.e., benzoyl or methyl-ethyl-ketone peroxide) is added. 

Powder coatings have been widely accepted in the industrial coating market because they are completely solvent free and show excellent mechanical and physical properties (13). Usually they contain a synthetic binder, a reactive cross-linker, pigments, and several additives to improve flow and other film eharacteristics. Various application techniques have been developed in reeent years. Powder coatings are normally sprayed electrostatically on grounded substrates and are heat-cured thereafter. Because these systems do not contain organic solvents, no emission of organic solvents takes place. However, the need for an oven to melt the resin and start the chemical reactions makes this environmentally friendly process unsuitable for do-it-yourself markets. 

Uses Reaction rate accelerator copolymerizes readily with most other vinyl monomers modifies hydrophilic properties in systems incl. adhesives, coatings, cosmetics, textiles, syn. fibers, textile sizes, protective colloids, lube oil additives reactive diluent in UV- and electron beam-curable systems (coatings, inks, adhesives) aids pigment disp. (inks) intermediate for modified phenolic resins of interest as plasticizers, dye intermediates, textile assistants... 

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