Coatings, urethane

This phosphoms-rich oligomer can also be incorporated into polyurethanes. Combinations with Eyrol 6 permit the OH number to be adjusted to typical values used in flexible foam, urethane coating, or reaction injection mol ding (RIM) appHcations (115,116). 

Polyols. Several important polyhydric alcohols or polyols are made from formaldehyde. The principal ones include pentaerythritol, made from acetaldehyde and formaldehyde trimethylolpropane, made from -butyraldehyde and formaldehyde and neopentyl glycol, made from isobutyraldehyde and formaldehyde. These polyols find use in the alkyd resin (qv) and synthetic lubricants markets. Pentaerythritol [115-77-5] is also used to produce rosin/tall oil esters and explosives (pentaerythritol tetranitrate). Trimethylolpropane [77-99-6] is also used in urethane coatings, polyurethane foams, and multiftmctional monomers. Neopentyl glycol [126-30-7] finds use in plastics produced from unsaturated polyester resins and in coatings based on saturated polyesters. 

Leather-like materials now important in the market are of three main classes (/) vinyl-coated fabrics, (2) urethane-coated (synthetic) fabrics, and (J) man-made leathers. To appreciate their leather-replacement capabiUties it is necessary to know the stmcture of natural leather. 

Fig. 5. Cross-sectional view of urethane-coated fabric with coagulated polyurethane layer.

Weight, Thickness, and Density. The thickness differs according to appHcation. Vinyl-coated fabrics are very heavy and dense. Urethane-coated fabrics and man-made leather are very light and two-thirds to one-half leather in density. 

Water-Vapor Permeability. Water-vapor permeabiUty depends on the polymer used for the coating layer and its stmcture. Vinyl-coated fabrics have Httie water-vapor permeabiUty due to the coating layer. Although polyurethane polymer is water-vapor permeable, urethane-coated fabrics also have low permeabiUty values due to their soHd layer stmcture. On the other hand, man-made leathers have good permeabiUty values as high as that of leather due to their porous layer stmcture. The permeabiUty of grain-type is lower than that of suede-type, influenced by finishing method. 

Urethane-Coated Fabrics. Manufacturing methods for urethane-coated fabrics are the dry system and the wet system. 

The production of coated fabrics including vinyl- and urethane-coated in the early 1980s is shown in Table 3 (4). Only production in the Far East showed an increase. The increase of urethane-coated fabrics mainly supports this tendency (Table 4). 

Table 4. Urethane-Coated Fabrics Production in the Far East ...

Alkan olamines ate used in urethane coatings for glass shatter proofing (68) and have been utilized as amides, salts, or free amines in providing antifrosting, antifogging, and dirt-resistant films on glass and plastics (69—72). 

Polymerization of castor od, chemical or oxidative, results in higher viscosity or bodied ods that are more usehd in urethane coatings than the untreated castor od (87). Other castor derivatives used to prepare urethanes are amides prepared by reaction of castor od and alkanolamines, amides of ricinoleic acid with long-chain di- and triamines, and butanediol diricinoleate (88,89). 

By varying molecular weight and functionaUty of the castor polyols and the type of isocyanate, a variety of clear and pigmented urethane coatings can be prepared. Copolymers of vinyl and castor-based urethane have also been reported for use as exterior coatings for plywood and flexible substrates (90) and for appHcation over steel, concrete, and wood substrates (91). 

Moisture-curable urethane systems (one-pack) can be considered as two-component systems which use atmospheric moisture as the second component. One-pack urethane coatings can be produced that are similar in physical properties to the two-pack systems for almost all applications. These highly complex systems can have a great deal of flexibility. Claimed advantages are a one-pack system, rapid cure, even at low temperatures, excellent chemical and abrasion resistance and good flexibility. Although these systems have been available for some time in other countries of Europe, they are only recently beginning to be of interest in the UK. 

Unsaturated polyester resins (UPRs) Uralkyd resins, 202 Urea-methylol reaction, 410 Urethane alkyds, 241 Urethane coatings, 202 Urethane elastomers, implanted, 207 Urethane foams, tests for, 244 Urethane gels, 205 Urethane-grade ATPEs, 223 Urethane-grade polyol types, 212 Urethane-grade raw materials, 246 Urethane hydrogel, preparation of, 250-251... 

The values of the three electrochemical measurements, potential, resistance, and current were measured for the four coatings over time. The resultant time series for each measurement and coating combination were analyzed by the Box-Jenkins ARIMA procedure. Application of the ARIMA model will be demonstrated for the poly(urethane) coating. Similar prediction results were obtained for all coatings and measurements, however, not all systems were modeled by the same order of ARIMA process. 

Figure 2 Partial Autocorrelation Function of Potential Data for Urethane Coating...

Post-Gel Examples. In addition to affecting the pre-gel viscosity, the presence of water (or humidity during cure) can also affect the cure response and final network structure formed in urethane coatings. Using reactions R1-R4, the following kinetic scheme can be written for cure of polyol-urethane coatings in the presence of humidity ... 

Figure 1. Weight average molecular weight versus % hydroxy reaction for a polyol-urethane coating with given percentages of isocyanate consumption by water.

Figure 3. Weighted concentration of effective strands for a typical polyol-urethane coating using the kinetics of Figure 2.

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