Coatings, solventless

Early latex paints were based on styrene-butadiene copolymers or poly(vinyl acetate). These have been largely supplanted by paints based on acrylic latices (acrylates, R00CH=CH2, or methacrylates, ROOCCH3=CH2), because of the acrylics superior chemical stability and, therefore, resistance to color change and degradation. 

The other approach to 100% solids coatings is to carry out the polymerization reaction right on the surface. Reactive liquid monomer or oligomer (low molecular weight polymer) is deposited on the surface and polymerized there. The reactants may be two components or a condensation pair (e.g., epoxies. Example 2.40, or polyurethanes. Example 2.4Q), which are mixed just prior to the application and heat-cured on the surface, or they may be unsaturated materials that undergo addition polymerization (acrylates, ROOC-CH=CH2, because of their high reactivity, are favored here). 

In radiation curing processes, addition reactions are activated by various forms of radiation infrared, microwave, radio frequency, gamma rays, ultraviolet (UV), and electron beam [2,3]. Basically, the energies of the first three are such that they simply thermally activate the system, that is, heat it, and are used in conjunction with the usual free-radical initiators. 

Gamma rays generate free radicals in polymer solutions (or in any solution for that matter) and are generated by the radioactive decay of certain elements, such as °Co. Due to the radioactivity, these systems are not frequently used, but the newly formed free radicals can effectively crosslink polymers in solution. However, the gamma rays also cause some degradation, so the resulting material may have reduced mechanical properties compared to other curing methods. 

This material, being tetrafunctional (two double bonds), will cure in an addition polymerization, but the crosslink density tends to be too low and, even though x is kept low, the viscosity is too high for many applications, so it is diluted with a multifunctional acrylate monomer such as trimethylol propane triacrylate  

This reduces the viscosity of the mix for easier application and increases the crosslink density in the cured film. 

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Powder coating is a solventless coating system that is not dependent upon a sacrificial medium such as a solvent, but is based on the performance constituents of solid TP or TS plastics. It can be a homogeneous blend of the plastic with fillers and additives in the form of a dry, fine-particle-size compound similar to flour. The three basic methods are the fluidized bed, electrostatic spray, and electrostatic fluidized bed processes (9). 

Linear oligoester diols can be used for solventless coatings (Jones, 1996). 

The acrylate or methacrylate functional PIBs have also been used in UV-curable solventless coatings formulation in the presence of reactive diluents (multifunctional acrylate or methacrylate esters) and a UV-sensitizer [104]. The products were transparent, flexible films, with very little extractables, in which hard polyacrylate or polymethacrylate domains were dispersed in the soft PIB matrix. Tensile strength and ultimate elongation have also been obtained. 

The products usually have to be flat for the most efficient processing. The high sensitivity of solventless coatings coupled with more efficient sources has enabled process speeds to attain 50-100 feet per minute. .2. 

The polyurethane derivatives used in solventless coatings and adhesives systems form a relatively small part of the market. There were about 50 million pounds sales in 1979, however, the solventless segment can be expected to grow at more than the 10fa rate expected for all polyurethane coatings adhesives. 

ATRP is an excellent method for the preparation of functional polymers. Polymers with molecular weights up to M =100,()00 can be obtained with narrow molecular weight distribution. Many functionalized styrenes, acrylates and other functional monomers were successfully polyineiized using a wide range of functional initiators or macroinitiators. Furthermore chain-end halogens can be displaced. Because of all these possibilities, ATRP can find applications in solventless coatings, adhesives, lubricants, surfactants and additives. 

At lesser rubber levels, heavy duty solventless coatings models based on dlethylenetrlamlne or fatty polyamide cures, showed elastomer-modification (10 phr rubber level) to advantage in Gardner impact, mandrel bend and corrosion-resistance testing (41). Impact testing (direct and reverse) gave 110 and 60 in-lbs, respectively for the rubber-modified fatty polyamide cured epoxy coating (14 days at R.T.), whereas a control formulation tested 10 in-lbs in each mode. 

Uses Epoxy base resin in flooring, casting, laminating, and high-build solventless coating appiics. 

Uses Surfactant, w/o or o/w emulsifier for cosmetic creams and lotions, textile spin finishes and lubricants, solv. and solventless coatings, paper defoamer formulations internal antistat for PP indirect food additive Features Self-dispersing... 

Uses Surfactant, emulsifier for paper defoamers, solv. and solventless coatings emulsifier, dispersant, opacifier, vise, control agent, defoamer for cosmetic, household prods., textiles, paper, water treatment Properties Yel. liq. HLB 8 acid no. 16 max. iodine no. 75-85 sapon. no. 115-125 pH 4 (5%) nonionic... 

Chem. Descrip. PEG-12 dioleate CAS 9005-07-6 EINECS/ELINCS 288-459-5 Uses Surfactant emulsifier for paper defoamers, solv. and solventless coatings lubricant for textile spin finishes Regulatory Avail, as kosher certified... 

Chem. Descrip. Modified cycloaliphatic amine Uses Epoxy curing agent for high-solids and solventless coatings and floors... 

Because the reactants are not diluted in solventless coatings, pot-lives are short (0 5-2 hours). Because of short pot-lives, special twin-feed airless spray equipment is often used. Aromatic polyamines are preferred for curing, so that hardening times of 4-12 hours can be obtained even at 0-10° C. This better low temperature cure cannot be obtained in outdoor topcoats, where colour is important, since the aromatic polyamines discolour. 

Powder coating is a solventless coating—a coating that is not dependent upon a sacrificial medium such as a solvent, but is based on the performance constituents of solid TP or TS resins. It can be a homogeneous blend... 

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