Polyurethanes chain extenders used

Almost all IDA derived chain extenders are made through ortho-alkylation. Diethyltoluenediamine (DE I DA) (C H gN2) (53), with a market of about 33,000 t, is the most common. Many uses for /-B I DA have been cited (1,12). Both DE I DA and /-B I DA are especially useful in RIM appHcations (49,53—55). Di(methylthio)-TDA, made by dithioalkylation of TDA, is used in cast urethanes and with other TDI prepolymers (56). Styrenic alkylation products of TDA are said to be useful, eg, as in the formation of novel polyurethane—polyurea polymers (57,58). Progress in understanding aromatic diamine stmcture—activity relationships for polyurethane chain extenders should allow progress in developing new materials (59). Chlorinated IDA is used in polyurethane—polyurea polymers of low hysteresis (48) and in reinforced polyurethane tires (60). The chloro-TDA is made by hydrolysis of chloro-TDI, derived from TDA (61). 

Phase II The phase I studies showed the potential of HER as a polyurethane chain extender. Excellent elastomers resulted with no processing problems. In phase II, the optimum catalyst and catalyst concentration was determined by curing one prepolymer, B-625, using a variety of tertiary amine and organo-tin catalysts. The results are shown in Tables VII and VIII. 

Table 5.8 Typical Chain Extenders Used in Syntheses of Polyurethane Bastomers...

Uses Intermediate solvent humectant coating resin raw material in paints crosslinking agent in polyurethane elastomers polyurethane chain extender intermediate for plasticizers, pharmaceuticals mfg. of tetrahydrofuran, terephthalate plastics elastomeric fabric coatings in food-pkg. adhesives Regulatory FDA 21CFR 175.105... 

Uses Intermediate in the prod, of nylon mfg. of hexamethylenediamine, polyesters, polyurethanes, paints polyurethane chain extender in gasoline refining as plasticizer solvent coupling agent coil coating Manuf./Distrib. Aldrich Allchem Ind. BASF Eastern Chem. Fallek Fluka Penta Mfg. 

Toxicology LD50 (oral, rat) 3.73 g/kg mod. toxic by ing. skin and eye irritant TSCA listed Precaution Combustible when exposed to heat or flame can react with oxidizers Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and fumes NFPA Health 1, Flammability 0, Reactivity 0 Uses Intermediate in the prod, of nylon, hexamethylenediamine, polyesters, polyurethanes, paints, pharmaceuticals polyurethane chain extender in gasoline refining as plasticizer solvent coupling agent coil coating... 

NMR [30] and mass spectroscopy [31] have been used to determine hard segment length in MDI-PTMO polyurethane chains extended with ethylene diamine. Monte Carlo simulations of Markov processes have also been used to derive hard segment molecular weight distributions under ideal and nonideal conditions [32-37]. 

The type of chain extender used was found to play a dominant role in the preparation of flexible, transparent polyurethanes, as mentioned previously. Use of low block ratios (i.e. low hard-segment content) was found necessary to obtain soft materials. However, soft-segment crystallization can result in opacity, so care is necessary. Samples T20, T21 and T22 of Table 12.4 are examples where soft-segment crystallization has occurred, and the resulting materials show opacity and high hardness. 

Uses. The largest uses of butanediol are internal consumption in manufacture of tetrahydrofuran and butyrolactone (145). The largest merchant uses are for poly(butylene terephthalate) resins (see Polyesters,thermoplastic) and in polyurethanes, both as a chain extender and as an ingredient in a hydroxyl-terminated polyester used as a macroglycol. Butanediol is also used as a solvent, as a monomer for vadous condensation polymers, and as an intermediate in the manufacture of other chemicals. 

In the second step, a papermaking method is also used for the fine fibers, less than 0.1 tex (1 den). This process is usually followed by a high pressure water jet process instead of the third step. In the fourth step, to obtain the required properties in specific appHcations, a polyurethane is selected out of the segmented polyurethanes, which comprises a polymer diol, a diisocyanate, and a chain extender (see Urethane polymers). A DMF—water bath for coagulation is also controlled to create the adequate pore stmcture in combination with fibers. 

Only a few commercial uses for TDA per se have been found. In epoxy curing appHcations, 2,4- I DA has been used as a component of a eutectic mixture with short chain aUphatic glycidal ether resins (46) as well as by itself (46,47) TDA (46) and single isomers (47) are also used as amine curatives. TDA can be used as a chain extender in polyurethanes (48,49). TDA is cited as a monomer in making aromatic polymers with unique properties, eg, amorphous polyamides (50), powdered polyamides (51), and low melting, whoUy aromatic polyamides (52). 

Almost all TDA use is as a chemical intermediate, mosdy in polyurethanes. Toluenediamine derivatives are found as all three components of urethanes isocyanates, chain extenders, and polyols (see Isocyanates, organic Urethane polymers). 

An entirely new concept was iatroduced iato mbber technology with the idea of "castable" elastomers, ie, the use of Hquid, low molecular-weight polymers that could be linked together (chain-extended) and cross-linked iato mbbery networks. This was an appealing idea because it avoided the use of heavy machinery to masticate and mix a high viscosity mbber prior to mol ding and vulcanization. In this development three types of polymers have played a dominant role, ie, polyurethanes, polysulftdes, and thermoplastic elastomers. 

In a second step, the prepolymer was then reacted with a low molecular weight difunctional alcohol, commonly referred to as a diol or a diamine, to connect the prepolymer oligomers into a high molecular weight polyurethane. This step was referred to as the chain extension , resulting in the use of the term chain extenders to describe the low molecular weight diols or diamines that reacted with the prepolymer oligomers. 

The chain extension step may then take place in the water phase. Hydrazine and ethylene diamine are commonly used chain extenders for waterborne urethane dispersions. The isocyanates react with the diamine chain extenders much faster than with the water, thus forming polyurea linkages and building a high molecular weight polymer. More detailed information regarding the synthesis and process of making waterborne polyurethane dispersions is found in Dieterich s review article [58]. 

The above prepolymer on treatment with 2 as the chain extender in dry DMF did not proceed at ambient temperature. The mixture had to be heated to 60°C for 3 h before the reaction was complete. After curing at 60°C for 24 h, the yellow, translucent block polyurethane film (BPUR2) again showed the absence of the —NCO peak in the IR spectrum indicating that curing had been complete. The fact that a higher temperature had to be used in the case of 2 as the chain extender compared to 1 is in keeping with the lower order of reactivity of diols with diisocyanates as compared to diamines with diisocyanates. 

We can make polyurethanes via one- or two-step operations. In the single-stage process, diols and isocyanates react directly to form polymers. If we wish to make thermoplastic linear polymers, we use only diisocyanates. When thermosets are required, we use a mixture of diisocyanates and tri- or polyisocyanates residues of the latter becoming crosslinks between chains. In the first step of the two-stage process, we make oligomers known as prepolymers, which are terminated either by isocyanate or hydroxyl groups. Polymers are formed in the second step, when the isocyanate terminated prepolymers react with diol chain extenders, or the hydroxyl terminated prepolymers react with di- or polyisocyanates. 

We create polyurethanes from prepolymers by chain extension. In the case of hydroxyl-terminated prepolymers the chain extender is an isocyanate. If we use a diisocyanate, the resulting polymer is linear. If we substitute some or all of the diisocyanate with a tri- or... 

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