Of polyurethanes

The polycondensation of di-isocyanates with polyhydric alcohols gives a wide range of polyurethanes which are used as artificial rubbers and light-weight foams, and have other important properties. Isocyanates are also used as modifiers in alkyd resins. ... 

Further nitration of the 2- and 4- isomers yields 2,4-dinitrotoluene, yellow crystals, m.p. 71 "C. This material is reduced to 2,4-di-aminotoluene and treated with phosgene to give 2,4-diisocyanatotoluene, a precursor of polyurethanes. 

PROPENE The major use of propene is in the produc tion of polypropylene Two other propene derived organic chemicals acrylonitrile and propylene oxide are also starting materials for polymer synthesis Acrylonitrile is used to make acrylic fibers (see Table 6 5) and propylene oxide is one component in the preparation of polyurethane polymers Cumene itself has no direct uses but rather serves as the starting material in a process that yields two valuable indus trial chemicals acetone and phenol... 

Polyurethanes. The hard portion of polyurethane consists of a chain extender and polyisocyanate. The soft component is composed of polyol segments. 

As a class of compounds, nitriles have broad commercial utility that includes their use as solvents, feedstocks, pharmaceuticals, catalysts, and pesticides. The versatile reactivity of organonitnles arises both from the reactivity of the C=N bond, and from the abiHty of the cyano substituent to activate adjacent bonds, especially C—H bonds. Nitriles can be used to prepare amines, amides, amidines, carboxyHc acids and esters, aldehydes, ketones, large-ring cycHc ketones, imines, heterocycles, orthoesters, and other compounds. Some of the more common transformations involve hydrolysis or alcoholysis to produce amides, acids and esters, and hydrogenation to produce amines, which are intermediates for the production of polyurethanes and polyamides. An extensive review on hydrogenation of nitriles has been recendy pubHshed (10). 

The physical properties of polyurethane adhesives result from a special form of phase separation which occurs in the cross-linked polyurethane stmcture. The urethane portions of polyurethanes tend to separate from the polyol portion of the resin, providing good shear strength, good low temperature flexibiUty, and high peel strength. Catalysts such as dibutyltin dilaurate [77-58-7], stannous octoate [1912-83-0], l,4-diazabicyclo[2.2.2]octane... 

Polyurethane. SmaU quantities of polyurethane film are produced as a tough mbber-like film. Polyurethane is more commonly used to produce foamed sheet, both flexible and rigid. The flexible foam is used as cushioning in furniture and bedding the rigid foam is widely used for architectural insulation because of its outstanding thermal insulation efficiency (see Urethane POLYMERS). 

Laboratory experiments using rodents, or the use of gas analysis, tend to be confused by the dominant variable of fuel—air ratio as well as important effects of burning configuration, heat input, equipment design, and toxicity criteria used, ie, death vs incapacitation, time to death, lethal concentration, etc (154,155). Some comparisons of polyurethane foam combustion toxicity with and without phosphoms flame retardants show no consistent positive or negative effect. Moreover, data from small-scale tests have doubtful relevance to real fine ha2ards. 

Adberabibty of the film may be enhanced by its treatment with flame, electric discharge, boron trifluoride gas, activated gas plasma, dichromate sulfuric acid, and a solution of alkab metal ia Hquid ammonia (84—87). A coating of polyurethane, an alkyl polymethacrylate, or a chlotinated adhesive can be apphed to PVF surfaces to enhance adhesion (80,88,89). 

Strengths and moduli of most polymers increase as the temperature decreases (155). This behavior of the polymer phase carried over into the properties of polymer foams and similar dependence of the compressive modulus of polyurethane foams on temperature has been shown (151). 

The sandwich-type stmcture of polyurethanes with a smooth integral skin produced by the reaction injection molding process provides a high degree of stiffness as weU as exceUent thermal and acoustical properties necessary for its use in housing and load-bearing stmctural components for the automotive, business machine, electrical, furniture, and materials-handling industry. 

Consumption of polyurethane foam in bedding reached a maximum in 1978 and has since declined. The innerspring mattress has remained the standard in the United States whereas aH-foam mattresses have gained a dominant market share in Europe. 

Another area ia which 1,4-cyclohexanedimethanol is commercially important is ia the manufacture of polyurethane foams (see Eoamed plastics). 

Organic Reactions. Nitric acid is used extensively ia iadustry to nitrate aHphatic and aromatic compounds (21). In many iastances nitration requires the use of sulfuric acid as a dehydrating agent or catalyst the extent of nitration achieved depends on the concentration of nitric and sulfuric acids used. This is of iadustrial importance ia the manufacture of nitrobenzene and dinitrotoluene, which are iatermediates ia the manufacture of polyurethanes. Trinitrotoluene (TNT) is an explosive. Various isomers of mononitrotoluene are used to make optical brighteners, herbicides (qv), and iasecticides. Such nitrations are generally attributed to the presence of the nitronium ion, NO2, the concentration of which iacreases with acid strength (see Nitration). 

Butanediol [110-63-4] (BDO) goes primarily into tetrahydrofuran [109-99-9] (THE) for production of polytetramethylene ether glycol (PTMEG), used ia the manufacture of polyurethane fibers, eg, Du Font s Spandex. THE is also used as a solvent for PVC and ia the production of pharmaceuticals (qv). Lesser amounts of BDO are employed ia the production of polybutylene terephthalate resias and y-butyrolactone. 

A. T. Chen, and co-workers, "Comparison of the Dynamic Properties of Polyurethane Elastomers Based on Low Unsaturation Polyoxypropylene Glycols and Poly(tetramethylene oxide) Glycols," Polyurethanes World Congress 1993, Vancouver, B.C., Canada, Oct. 10—13,1993. 

S. H. Harris, P. E. Kreter, and C. W. Podey, "Characterization of Polyurethane Eoam Odor Bodies," Polyurethanes World Congress 1987, Aachen,... 

Step-growth polymerization is characterized by the fact that chains always maintain their terminal reactivity and continue to react together to form longer chains as the reaction proceeds, ie, a -mer + -mer — (a + )-mer. Because there are reactions that foUow this mechanism but do not produce a molecule of condensation, eg, the formation of polyurethanes from diols and diisocyanates (eq. 6), the terms step-growth and polycondensation are not exactly synonymous (6,18,19). 

Until the mid-1960s, phenylenediamines were used primarily for oxidative purposes the para isomer was of major importance. Since then, the use of phenylenediamines to manufacture polymers has far exceeded their use for oxidative purposes. The y -phenylenediamines, (2,4 and 2,6)-toluenediamine, are widely used for the manufacture of polyurethanes. Phenylenediamines are dihinctional and react with other dihinctional compounds, such as dianhydrides, diacyl chlorides, dicarboxyHc acids, and disulfonyl chlorides to give polyamides. Phenylenediamines also give polymers with epoxides, diols, diacetals. 

The y -phenylenediamiaes are easily obtained by dinitrating, followed by catalyticaHy hydrogenating, an aromatic hydrocarbon. Thus, the toluenediamiaes are manufactured by nitrating toluene with a mixture of sulfuric acid, nitric acid, and 23% water at 330°C which first produces a mixture (60 40) of the ortho and para mononitrotoluenes. Further nitration produces the 80 20 mixture of 2,4- and 2,6-dinitrotoluene. Catalytic hydrogenation produces the commercial mixture of diamiaes which, when converted to diisocyanates, are widely used ia the production of polyurethanes (see Amines, aromatic, DIAMINOTOLUENES) (22). 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Propylene oxide (qv) uses include manufacture of polyurethanes, unsaturated polyester, propylene glycols (qv) and polyethers, and propan o1 amines (see Alkanolamnes Glycols Polyethers Polyesters, unsaturated Urethane polyt rs). 

The advent of newer polyurethane materials is expected to lead to a new generation of cardiovascular devices. The characteristics of polyurethanes, combined with newer manufacturing techniques, should translate into direct medical benefits for the physician, the hospital, and the patient. This field offers exciting growth opportunities. 

Sucrose acrylate derivatives can be converted into polymers and hydrogels that can be used as flocculants, water adsorbents, bioimplantables, and dmg dehvery devices (42). Sucrose ethers have appHcations as surfactants and surface coatings, and as feedstocks for synthesis of polyurethane foams and... 

Dimethyl sulfoxide can also be used as a reaction solvent for other polymerizations. Ethylene oxide is rapidly and completely polymerized in DMSO (85). Diisocyanates and polyols or polyamines dissolve and react in DMSO to form solutions of polyurethanes (86) (see Solvents, industrial). 

The avadabihty of PMDI also led to the development of polyurethane-modified isocyanurate (PUIR) foams by 1967. The PUIR foams have superior thermal stabiUty and combustibiUty characteristics, which extend the use temperature of insulation foams well above 150°C. The PUIR foams are used in pipe, vessel, and solar panel insulation glass-fiber-reinforced PUIR roofing panels having superior dimensional stabiUty have also been developed. More recently, inexpensive polyester polyols based on residues obtained in the production of dimethyl terephthalate (DMT) have been used in the formulation of rigid polyurethane and PUIR foams. 

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