Polymerization of polyurethane

Miller J.A., Speckhard T.A., Homan J.G., and Cooper S.L. Monte Carlo simulation study of the pol3mier-ization of polyurethane block co-polymers. 4. ModeUng of experimental data. Polymer, 28, 758, 1987. Speckhard T.A., Miller J.A., and Cooper S.L., Monte Carlo simulation study of polymerization of polyurethane block co-pol3miers. 1. Natural compositional heterogeneity under ideal polymerization condition, Macromolecules, 19, 1550, 1986. 

Figure 2.10. Temperature increase in adiabatic polymerization of polyurethane accompanied by the formation of interpenetrating networks in the polyurethane-unsaturated polyester system.

A primary amine has one ammonia hydrogen substituted (e.g., methylamine). Primary amines are used as a catalyst and solvent in the manufacture of resins. They are also used as an isocyanate coreactant in the polymerization of polyurethane. 

Figure 733 DeterminaKon of heat of polymerization of polyurethane (polyol + polyisocyanate) [3]...

Polyurethanes are condensation polymers formed by step-growth polymerization in which the chain length of the polymer increases steadily as the reaction progresses. Two major routes of polymerization of polyurethanes are one-step and two-step synthesis methods. In one-step synthesis, the diisocyanate, polyol, and a chain extender are mixed together and allowed to react. In the two-step route, an oligomer or prepolymer synthesized from diisocyanate and polyol and the chain extender are allowed to react. The two-step route offers some advantages over the one-step route, such as a reduced polydispersity index and a higher extent of phase separation. 

Two-component, catalyzed, interfacial polymerization of polyurethane has been previously modeled by means of a set of partial differential equations for the diffusion-reaction process, with concentration-dependent difiusivities [105-108]. Their main assumptions were that reactions were fadlitated only toward the end of the mixing process, such as at the end of the reaction injection-molding process, wherein molecular diffusion was significant. It was also assumed that the diisocyanate and diols formed lamellar mixing structures, whereby alternative striations of diisocyanates and diols were present. 

The applications of the strong affinity to oxygen of organotin compounds are as catalysts. Organotin compounds are used for the polymerization of polyurethanes, polymerization of silicones and esterifications as the catalysts [62,63,65]. The catalysts for reactions of phenylisocyanate with butanol as a basic reaction of polyurethane formation reaction are shown in Table 10.5 [78]. The reaction rate with dialkyItin compounds are 30000-80000 times faster compared with the reaction without a catalyst. The urethane is considered to be formed via the following four center mechanism [79]. 

Similarly, the polymerization of polyurethane does not involve the evolution of a condensation product, even though its kinetics can be described by that of condensation polymerization. Clearly, it is not correct to classify polymers according to the scheme discussed earlier. It is now established that there are two classes of polymerization mechanisms ... 

In this research, a novel semi-interpenetrating networks electrolyte has been developed by a solvent-free reactive process. A flexible amorphous polyether modified polysiloxane is incorporated in polyurethane and form semi-interpenetrating network (IPN) structure by in-situ polymerization of polyurethane with the presence of PEMPS and salts. The monomer of polyurethane, polyol, functions as the common solvent to dissolve the salts so no additional volatile solvent is needed in this reactive process. The addition of PEMPS is expected to improve the ionic conductivity of polyurethane due to its high ionic conductivity and the decrease in crystalinity of soft segment of polyurethane as well as the generation of the high conductive interface. 

Foams. Polyurethane foams are prepared by the polymerization of polyols with isocyanates. 

HydroxyethyUiydrazine (11) is a plant growth regulator. It is also used to make a coccidiostat, furazoHdone, and has been proposed, as has (14), as a stabilizer in the polymerization of acrylonitrile (72,73). With excess epoxide, polysubstitution occurs and polyol chains can form to give poly(hydroxyaLkyl) hydrazines which have been patented for the preparation of cellular polyurethanes (74) and as corrosion inhibitors for hydrauHc fluids (qv) (75). DialkyUiydrazines, R2NNH2, and alkylene oxides form the very reactive amineimines (15) which react further with esters to yield aminimides (16) ... 

The polymerization of tetrahydrofuran was first studied ia the late 1930s (3,4). In 1960, this work was summarized (4), and the Hterature on tetrahydrofuran polymers and polymerization has been growing ever siace. Polytetrahydrofuran with hydroxy end groups has become a large-scale commercial product, used mainly as the flexible polyether segment ia elastomeric polyurethanes and polyesters. It is commercially available under the trade names Terathane (Du Pont), Polymeg (QO Chemicals), and PolyTHF (BASF). Comprehensive review articles and monographs have been pubUshed (2,5-8). 

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). 

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). 

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). 

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

A new ionic polymeric polycarbamate was synthesized after steps of polyurethane chemistry using 3-iso-cyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate, 2,5-dimethyl-2,5-dihydroperoxyhexane, 1,6-butanediol, 2,4-tolylenediisocyanate, and N,N -bis(j3-Hydroxy-ethyOpiperazine [27]. Modification of the nitrogen of the piperazine ring into quaternary ammonium salt by treatment with methyliodide gave the MPI high electroconductivity. 

Polymerized Alcohols. Polyhydric alcohols (qv) such as pentaerythritol, sorbitol and glycerin can be used as the polyol component of polyethers (qv) which are used as expl and propint binders. Polyoxypropylene derivs of sorbitol have been employed extensively as components of polyurethane resins (qv), also employed as a propint binder... 

The history of polyurethanes begins with Otto Bayer3 at Germany s I. G. Farben-industrie (tire predecessor company of Bayer AG4) in 1937, tire year of tire first disclosure of diisocyanate addition polymerization to form polyurethanes and polyureas. The main impetus for this work was tire success of Wallace Caro titers... 

Polyurethanes are thermoset polymers formed from di-isocyanates and poly functional compounds containing numerous hydroxy-groups. Typically the starting materials are themselves polymeric, but comprise relatively few monomer units in the molecule. Low relative molar mass species of this kind are known generally as oligomers. Typical oligomers for the preparation of polyurethanes are polyesters and poly ethers. These are usually prepared to include a small proportion of monomeric trifunctional hydroxy compounds, such as trimethylolpropane, in the backbone, so that they contain pendant hydroxyls which act as the sites of crosslinking. A number of different diisocyanates are used commercially typical examples are shown in Table 1.2. 

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