Coating polyurethane

It has been found that the photoinitiation rates of acrylic urethane and acrylic melamine coatings depend primarily upon the nature and concentration of chromophores that are incorporated into the acrylic copolymer during polymerization [731, 732]. The primary chromophores for conventional polymerization (peroxide and hydroperoxide initiators in ketone solvents) are ketonic end-groups [359, 735]. 

The rate of photo-oxidation in both urethane and melamine crosslinked coatings was found to be Unear with hydroperoxide concentration [190, 1478]. In urethane coatings, the photo-oxidation rate reaches zero with zero hydroperoxide concentration whilst in melamine coatings there is a residual photo-oxidation rate at zero hydroperoxide concentration. This residual photo-oxidation appears to be related to melamine photochemistry. 

Other variants of technical interest include blocked reactive groups, that can be activated by heat or atmospheric moisture. Microencapsulation of polyisocyanates is also becoming a deactivation method. 

Depending on their chemical composition, polyurethane paints are formulated as two-component (two-pack) or one-component (one-pack) mixtures. They are applied from the liquid phase, which may be solvent-containing, aqueous, or solvent-free, or from the solid phase as a powder coating. They may be cured under a wide range of conditions drying above to stoving at ca. 200°C. 

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Water-borne polyurethane coatings are formulated by incorporating ionic groups into the polymer backbone. These ionomers are dispersed in water through neutrali2ation. The experimental 1,12-dodecane diisocyanate (C12DI Du Pont) is especially well suited for the formation of water-borne polyurethanes because of its hydrophobicity (39). Cationomers are formed from IPDI, /V-methyIdiethan olamine, and poly(tetramethylene adipate diol)... 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

The acetates of most alcohols are also commercially available and have diverse uses. Because of their high solvent power, ethyl, isopropyl, butyl, isobutyl, amyl, and isoamyl acetates are used in ceUulose nitrate and other lacquer-type coatings (see Cellulose, esters). Butyl and hexyl acetates are exceUent solvents for polyurethane coating systems (see Coatings Urethane polymers). Ethyl, isobutyl, amyl, and isoamyl acetates are frequentiy used as components in flavoring (see Flavors and spices), and isopropyl, benzyl, octyl, geranyl, linalyl, and methyl acetates are important additives in perfumes (qv). 

Effete of silanes on bond strength of polyurethane coatings... 

A typical application of these coatings is the use on carrier pipes installed by thrust boring techniques at major road, rail and river crossings. Sprayed polyurethane coatings of 900 thickness, are also commercially available on ductile iron pipes. 

Example 9. Two-Component Waterborne Polyurethane Coating. This example utilizes the PUD from Example 8 in a two-component, waterborne coating formulation. An HDI-based, water-dispersible isocyanate is also prepared. 

Polyureas, 197 Polyurethane catalysis, 228 Polyurethane coatings, 202, 203 preparation of, 254-255... 

Turner, S. Richard, 1 Two-component (2-K), nonsagging, polyurea structural adhesive, preparation of, 255-256 Two-component (2-K) systems, 238-241 Two-component (2-K) waterborne polyurethane coatings, 206 preparation of, 254-255 Two-shot cast elastomer, preparation of, 249-250... 

With a minimum of analytical measurements, the effect of several parameters on the curing of polyurethane coatings can be studied using the presented model. 

Most of the hexamethylenediamine produced is used for the manufacture of Type 66 nylon by polymerization with adipic acid. A minor use is for the preparation of hexamethylene diisocyanate used in light-stable polyurethane coatings. 

Adhesive-Coated Material. The addition of an adhesive-coated material [335] to proppants decreases the flowback of the particulates. Such adhesive-coated materials can be inorganic or organic fibers, flakes, and the like. The adhesive-coated material interacts mechanically with the proppant particles to prevent the flowback of particulates to the wellbore. The consolidation of a proppant also may occur via a polyurethane coating, which will slowly polymerize after the fracturing treatment because of a polyaddition process [1856]. 

Karlsson D, Spanne M, Dalenea M, Skarping G (2000) Airborne thermal degradation products of polyurethane coatings in car repair shops. J Environ Monit 2 462 169... 

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