Polyureas, coatings

Example 6. High Solids, Two-Component, Clear, Aliphatic, Polyurea Coating. This example of an aliphatic, 100% urea coating utilizes polyaspartic esters as reactive diluents (see Section 4.2.3). These compounds allow fine tuning of reactivity and physical properties and eliminate the need for viscosity-reducing solvents. 

Example 7. Solvent-Borne, One-Component, Moisture-Cure, Aliphatic Polyurea Coating. This example is of a more traditional one-component coating formulation using a volatile solvent as a diluent. The active ingredient is a modified HDI, Desmodur N-75 BA from Bayer. 

High-solids, two-component, clear, aliphatic, polyurea coating, preparation of, 252-253 High-temperature annealing, 220 High-temperature bulk polyesterifications, 61-74... 

T. Kenworthy. Polyurea coatings for offshore oil rigs in the Gulf of Mexico. Mater Performance, 40(10) 40-42, October 2001. 

Fig. 1.5.10 Transmission electron micrographs of two different thicknesses of polyurea coating on titania core particles. In each case the titania was obtained under the same conditions as those in Fig. 1.5.3. HDI was kept at 80°C at flow rates of (A) 0.19 dm3 min-1 and (B) 0.42 dur1 min-1. The flow rate and temperature of ethylenediamine were held constant at 44.3 cmJ min-1 and 25°C, respectively. (From Ref. 39.)...

PROPERTIES OF SPECIAL INTEREST Polyurea fibres have high melting points, low specific gravity, excellent dyeabiHly, and good acid and alkaline resistance. Polyurea coatings have lower solvent and better water resistance compared to polyurethanes. They have good blood compatibility. 

S.W. Guan. 100% solids polyurethane and polyurea coatings technology Chemistry, selection, and application. In the Proceedings of the 2nd China International Corrosion Control Conference, Beijing, P.R. China, November 4—8, 2002. 

DDI has low toxicity and high resistance to moisture it reacts with diamines to form polyurea coatings that are internally plasticized and have excellent resistance to moisture and to yellowing by ultraviolet light. Besides coatings, important application fields for dimer diisocyanates, are polyurethane implants like stents or heart-assist devices and PUR rocket propellant liners or sealants. 

Ionic polymers are also formulated from TDI and MDI (43). Poly(urethane urea) and polyurea ionomers are obtained from divalent metal salts of /)-aminohen2oic acid, MPA, dialkylene glycol, and 2,4-TDI (44). In the case of polyureas, the glycol extender is omitted. If TDI is used in coatings apphcations, it is usually converted to a derivative to lower the vapor pressure. A typical TDI prepolymer is the adduct of TDI with trimethyl olpropane (Desmodur L). Carbodiimide-modified MDI offers advantages in polyester-based systems because of improved hydrolytic stabihty (45). Moisture cure systems based on aromatic isocyanates are also available. 

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... 

Finally the aerosol process could be used to coat particles, as exemplified in the system of titania cores and polyurea shells (39). In this case the titania particles were generated from Ti(IV) ethoxidc as described earlier, then contacted with dried... 

Two-part sprayable polyurethanes are used in the production of chemical-resistant paints and coatings. The polyurethanes can be let down in some solvent to ease in the spraying. Polyureas are becoming important in this section of the market because of their very fast cure rates. 

Giraud, S., Bourbigot, S., Rochery, M., Vroman, I., Tighzert, L., Delobel, R., and Poutch, F. 2005. Flame retarded polyurea with encapsulated ammonium phosphate for textile coating. Polym. Deg. Stab. 88 106-113. 

In a recently published work by Bourbigot et al.,63-65 microencapsulation of ammonium phosphate with PU and polyurea shells has been carried out to make an intrinsic intumescent system compatible in normal PU coating for textiles. Microencapsulation of ammonium phosphate helps in reducing the water solubility of the phosphate and hence, increases the durability of the textile back-coating. 

Hohberg T, Schaefer O, Mueller J et al. (2003) Textiles coated or finished with polysiloxane-polyurea-polyurethane block copolymers (Wacker-Chemie G.m.b.H., Germany) EP1336683. 

Note by the author Most Aerospace coatings require resistance to hydraulic liquids over-indexing permits an increase in polyurea groups in the network that is not soluble in the hydraulic liquid. 

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