Di-or poly-isocyanate

Di or poly)chlorides + (Di or poly)amines Polyamides (Di or poly)isocyanates + (Di or poly)amines Polyureas (Di or poly)isocyanates + (Di or poly)ols Polyurethane (Di or poly)acyl Chlorides + (Di or poly)ols Polyesters Bischloroformates + (Di or poly)amines Polycarbonates... 

Polyurethane is a collective term for a group of polymers that contain an urethane group (-NH-COO-). They are generated from a reaction between polyesters and polyethers with di- or poly-isocyanates. 

The traditional synthesis of PUs involves a step polymerization between a di- or poly-isocyanate with a diols/polyols. A Hnear polymer is obtained if di-functional isocyanates and polyols are used (see Figure 12.11). Both the isocyanates and polyols used to make polyurethanes contain on average two or more functional groups per molecule. 

Polyurethanes (PUR or PU) are traditionally and most commonly formed by reacting a di- or poly-isocyanate with a polyol in a polyaddition reaction. While most polynrethanes are thermo-setting polymers that do not melt when heated, thermoplastic polyurethanes are also available. 

A di- or poly isocyanate, usually in solution, is applied to the surface of an adherend prior to its contact with other adherend member(s) similarly coated. 

A stable, blocked di- or poly isocyanate in suspension, including aqueous suspension, or solution is applied alone (as in Method A), in combination with a conventional plastic or rubber vehicle (as in Method B), in combination with a di- or polyhydroxy material (as in Method C), or in combination with a preformed polyurethane vehicle (as in Method D) to adherend surfaces. The coating is dried, the coated adherend surfaces contacted, and the assembly heated to decompose the blocked isocyanate. This generates free di- or polyisocyanate which proceeds to bond the adherend directly and through reaction with the vehicle which may be a pre- or in situ-formed polyurethane. The cleaved blocking agent diffuses into the surrounding matrix or escapes into the air. 

Di- and poly-isocyanates are mainly used in the production of polyurethane rigid or flexible foams (for insulation and in furniture), adhesives, sealants, surface coatings, elastomers and fibres [2007,2072,2165], whilst mono-isocyanates are employed in the synthesis of substituted ureas and carbamates (Section 4.7.3) for medicinal, agricultural and other... 

Two-package polyol urethane coatings (ASTM type 5). Here, the curing involves reaction between isocyanate-terminated adducts and di- or poly-functional hydroxyl-containing prepolymers having different backbone structures. 

Reaction polymerization reactions of isocyanates with suitable monomers can he performed in an extruder or in a RIM machine. In the latter reaction thermosets (cross-hnked polymers) are produced. In an extruder usually linear polymers are manufactured. For example from methylene di-p-phenylene isocyanate (MDI), with some macroglycols and 1,4-hutanediol as extenders, segmented polyurethane elastomers are produced in an extruder (6). However, linear condensation polymers are also produced in a vented extruder. For example from MDI, with macrodicarboxylic acids and dicarboxyhc acids as extenders thermoplastic block copolyamide elastomers are produced. The by-product of the condensation reaction, carbon dioxide, is removed in the vented extruder. The polycondensation process can also be performed in solution. For example, MDI can be added to a solution of dicarboxyhc acids in tetramethylene sulfone, with simultaneous removal of the carbon dioxide. Tetramethylene sulfone is the solvent of choice for solution polymerization of isocyanates (7). In addition to dicarboxyhc acids trimellitic acid anhydride and benzophenonetetracarboxylic acid dianhydride (BTDA) are utilized as monomers for condensation polymers. With these monomers poly(amide imides) and poly(imides) are produced. The diisocyanate-derived commercial polycondensation products are listed in Table 1. 

A recent patent application disclosed a method for making polyurethanes made from nitrite esters and di/poly-isocyanates with the help of UV-irradiation for use as coatings. The application disclosed polymerizable and curable compositions and processes of polymerizing and curing polyurethanes involving an isocyante compound and a nitrite ester compound. Irradiation of the nitrite ester compound with UV generates an active hydrogen compound by the Barton nitrite photolysis reaction that reacts with an isocyanate compound to produce and/or crosslink a polyurethane. 

A typical polyester could be poly (diethyleneglycol adipate) with a molecular weight of between 2000 and 3000. A typical polyether is obtained by polymerisation of propylene oxide, usually in the presence of a small proportion of glycerol or sorbitol to provide branched structures. Two of the most commonly used isocyanates are 2,4- and 2,6- tolylene di-isocyanate (TDI). These are chosen because of their reactivity, cheapness and relative low toxicity. The resulting prepolymer has -OH terminal groups when a deficiency of isocyanate is used, but -NCO terminal groups if an excess of isocyanate is employed. 

Reaction with difunctional amines (see the next paragraph) allows the formation of poly (urethane-co-urea) and further extends the versatility of the segment architecture. For further control of the structure, a prepolymer is formed. The reaction, such as the polyurethane reaction shown above, is carried out with excess di-isocyanate so that an isocyanate-terminated prepolymer is obtained. The isocyanates used are typically aromatic, such as toluene di-isocyanate. This prepolymer is then reacted with a short-chain diol or diamine (for a polyurea) to form the final polymer. 

The earlier example of the formation of a poly(urethane-co-urea) showed the change in properties made possible by including a comonomer (in that case a difunctional amine) together with the usual diol for reaction with a di-isocyanate. This can be extended to a wide range of step polymerizations where an additional reactant is added. Examples could be the use of two AB-type monomers (e.g. amino acids) or two AA (e.g. diacids) to react with one BB (a diamine) to form co-polyamides. Seveml features of step polymerization help in understanding the resultant copolymer. For example, since high-molar-mass polymer is formed only late in the reaction, the composition of the copolymer will be that of the feed ratio of the monomers. 

Chemistry Polyurethane is produced by the reaction of a polyol with an diisocyanate (or in some instances a polyisocyanate) in the presence of catalysts. The polyols of choice are poly(propylene glycol), block copolymers of ethylene oxide (10-15%) with propylene oxide, or the newer polymer polyols (based on polymers such as polystyrene or styrene-acrylonitrile copolymer). Polyester diols such as polycaprolactone diol can be used in place of the polyether polyol in this reaction. The isocyanate of choice is a mixture of the 2,4 and 2,6 isomers of tolylene di-isocyanate in the ratio of 80 20, generally referred to as 80 20TDI. Other isocyanates such as diphenylmethane di-isocyanate (MDI), hexamethylene di-isocyanate (HMDI), and isophorone di-isocyanate (IPDI) are also used. A tin-based or amine catalyst is used to promote the reaction. Given the wide choice of reactants available, the reaction can yield foams with a range of different mechanical and thermal characteristics. 

Direct addition pol3mieri2ation of 2-amino-2-deoxy-D-glucose and a diisocyanate (4,4 -methylene-diphenyl-l, 1 -di-isocyanate, phenyl-1,4-di-isocyanate, toluene-2,4-di-isocyanate, or butyl-1,4-di-isocyanate) yields a linear sugar-containing poly(urea-urethane) (5) having good solubility in organic solvents, unlike chitin or chitosan. ... 

Klemm and Stockle in the convenient preparation of thiol- and isocyanate-terminated thiocarbamate prepolymers, as depicted in Scheme 2.4 (Klemm and Stockl, 1991). By varying the stoichiometry, either di-thiol or di-isocynate functional poly(thiourethane)s could be assembled within 1 h at ambient temperature. 

Raffa P, ColtelUM-B SS, Bianchi S, Castelvetro V. Chain extension and branching of poly (ethylene terephthalate)(PET) with di-and multifunctional epoxy or isocyanate additives An experimental and modelling study. React Funct Polym 2012 72 50-60. 

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