Polyurethane obtaining

Table 9.2 summarizes some technological characteristics of typical one-pack and two-pack FBZ formulations, as well as the curing conditions. Viscosity is sufficiently tow and suitable for spray or roll applications. In most cases, high-solid coatings can be obtained. The materials described herein include the bicomponent polyurethanes obtained by addition of Z1030 to Z1072 or Z1073... 

Urethanes obtained from aromatic diisocyanates undergo slow oxidation in the presence of air and ligh t, causing discoloration, which is unacceptable in some applications. Polyurethanes obtained from aliphatic diisocyanates are color-stable, although it is necessary to add antioxidants and nv-stabilizers to the formulation to maintain the physical properties with... 

Homogeneous ideal networks, also called closed networks, result from a single-step polymerization mechanism of a stoichiometric mixture of monomers, reacted to full conversion. Many amine-crosslinked epoxies of Tg < 200°C and polyurethanes obtained using a single isocyanate monomer and a single polyol belong to this family. 

Before going into the methods for radical reactions it most be said tlmt polycondensation or polyaddition have led to more industrial preparation. In this connection epoxy resins, the polyurethanes obtained from prepolymers and, more recently, more specialized polymers such as the PEB AC (ATOCHEM), amid-ether or polyimids (KHERIMIDE from RHONE POULENC must be mentioned). Moreover, it is interesting to note that the ionic methods (cationic or anionic ones) have not produced industrial products (except dihydroxy poly (dimethyl siloxanes), poly (tetrahydro-furanes)) but they have facilitated theoretical studies both on the analytical aspects and the materials we can obtain. 

Pellethane CPR 2102 polyurethane, obtained from the Upjohn Company, was the other polyurethane studied. (Hereafter this material Is referred to as polymer "B .) For polymer B the molar ratio of polyester to MDI Is 2.95, and the ester Is poly(capro-lactone). This material Is reported to have Initial properties similar to polymer A when both materials are post cured at llO C for 16 hours. The polymer B samples were previously post cured. 

The network polyurethane obtained by reacting a diisocyanate R(N=C=0)2 with pentaerythritol C(CH20H)4 contains, according to elemental analysis, 0.2% (w/w) nitrogen and has a density of 1.05 g/cm. Determine (a) polymer chain segment density in mol/cm, and (b) molar mass of chain segments between branch points. 

We found that the polyurethane obtained by reacting poly(do-decamethylene D-tartrate) with 1,6-di-isocyanatohexane supported the growth of A. niger with an ASTM rating of 4 (16). A similar polyurethane derived from poly(hexamethylene tartrate) was degraded in vivo... 

X 10 mass fraction of KEP-2. All the polyurethanes obtained in the presence of surfactant are characterized by the disappearance of the emulsion structure observed in the initial polyurethane. 

The first polyurethane obtained by FP has been derived by the reaction between 1,6-hexamethylene diisocyanate (HDI) and ethylene glycol (EG) in the presence of dibutyltin dilaurate (DBTDL) as a catalyst, and pyrocatechol as an additive necessary for ensuring a sufficiently long pot-life (25). Indeed, if this latter compound is not present, instantaneous SP occurs. Furthermore, fingering was avoided by adding 3 wt.-% fumed silica (Cabosil ) to the above components dissolved in 18 wt.-% dimethylsulfoxide (DMSO). 

Bueno-Feirer, C. Hablot, E. Peirin-Sarazin, R Gairigos, M. C. Jimenez, A. Ave-rous, L. Structure and morphology of new bio-based thermoplastic polyurethanes obtained from dimer fatty acids. Macmmolecular Materials and Engineering, 2012, 297(8), 111-19A. 

As with the nylons, the polyurethanes obtained from hexamethylene diisocyanate and 1,4-butanediol may be used as thermoplastic moulding materials. Mouldings from these materials resemble those from nylon 6,6 but have lower water absorption and hence better dimensional stability and retention of electrical insulating properties in humid conditions. These materials are more expensive than the nylons and have found limited application for small mechanical components such as bearings and gears. 

Polyurethanes obtained from renewable resources, such as carbohydrates, have attracted much attention in recent years [110,111]. This new interest results from great biomass access and their potential as replacements for some petroleum-based polymer precursors. The polymers obtained from natural products are expected to be biodegradable and non-toxic. The inclusion of hydrophilic monomers, such as carbohydrates, into the polymer chain facilitates water attack, increasing the hydrolytic degradation. 

Recently in our group, Le Bris [73] described the synthesis and the optical properties of a high molecular weight polyurethane obtained by the interfacial procedure between (-)-diamino-1,2-propane and adipyl bis-chloroformate in the presence of sodium carbonate and sodium lauryl sulfate as, respectively, acceptor and emulsifier following Scheme XXXVI. 

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