Polyol-based polyurethanes

The superior characteristics of polyester polyol based polyurethanes are explained by a better crystalline structure [1, 7] in the urethane segment, compared to the majority of poly ether polyols which are amorphous [except polytetrahydrofuran (PTHF)], due to the superior secondary forces between the polyester chains [8] and also due to a superior thermal and fire resistance, compared to polyether polyol based polyurethanes. Polyester-based polyurethanes (flexible foams, coatings), have a superior solvent resistance compared to the polyether-based polyurethanes [8]. 

Biostability increases strongly by changing to polyether polyol based polyurethanes. Generally the polyethers are relatively non-toxic but nonbiodegradable products. 

S. Obruca, I. Marova, L. Vojtova, Biodegradation of polyether-polyol-based polyurethane elastomeric films influence of partial replacement of polyether polyol by biopolymers of renewable origin, Environ. Technol. 32 (9-10) (2011) 1043-1052. 

Using this technique, a large variety of polyurethanes have been prepared from different vegetable oils. Natural polyols like castor oil (generally trifunctional) are directly reacted with diisocyanates to obtain branched polyurethanes, although it is difficult to control the reactivity. However, bifunctional castor oil can be polymerised with diisocyanates in the presence of suitable chain extenders and catalysts to produce polyurethanes in a more controlled manner (Fig. 6.4). A castor oil polyol-based polyurethane network can also be prepared from epoxy terminated polyurethane pre-polymer with 1,6-hexamethylene diamine. Epoxy terminated pre-polymer is obtained by the reaction of glycidol and isocyanate terminated polyurethane pre-polymer of castor oil polyol, poly(ethylene glycol) (PEG) and 1,6-hexamethylene diisocyanate. ... 

A natural polyol of alcoholysed castor oil with triethanolamine-based rigid polyurethane foam and wood flour composite was prepared and found to show a decrease in compression modulus and yield strength with an increase in wood flour content, although good interaction of wood flour with isotyanate was noticed. Tung oil polyol-based polyurethane with pine wood flour composite was also reported. ... 

Carbohydrates such as saccharose, D-glucitol, and diaminosaccharides such as trehalose, have been widely used for the syntheses of highly functionalized polyol-based polyurethanes. The preparation of pol5Uirethanes by the reaction of dianhydrohexitols with aliphatic diisocyanates was explored in 1983, and technical applications of dianhydrohexitols were found as chain extenders in polyurethane syntheses, as patented. 

Banik, I. and M. M. Sain. 2008. Water blown soy polyol-based polyurethane foams of different rigidities. J. Reinf. Plast.Comp. 27 357-373. 

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. 

Fig. 22 Respirometry of vegetable oil-based polyurethanes made from the following polyols triolein-met arrowhead), soy-HF (filled square), soy-met 180 (open diamond), soy-met 206 (open circle), and linseed met (open square). Also shown is ESO/BF3 polymer (open triangle) and soybean oil control (filled circle). Temperature was increased from 30°C to 55°C on day 71. Note that hydroxyl number of 180 has the functionality of 3.3 and that of hydroxyl 206 is 4.0. Met refers to polyol made from ESO and methanol HF refers to polyol from hydroformylation and reduced ESO. Reproduced from [152] by permission of Journal of Polymers and the Environment...

Fully cured polyurethanes present no health hazard they are chemically inert and insoluble in water and most organic solvents. Dust can be generated in fabrication, and inhalation of the dust should be avoided. Polyether-based polyurethanes are not degraded in the human body, and are therefore used in biomedical applications. Some of the chemicals used in the production of polyurethanes, such as the highly reactive isocyanates and tertiary amine catalysts, must be handled with caution. The other polyurethane ingredients, polyols and surfactants, are relatively inert materials having low toxicity. 

Let us now analyze the application of this technique to the formation of a polyurethane synthesized from toluene diisocyanate (TDI, a mixture of 80% toluene 2,4- diisocyanate and 20% toluene 2,6-diisocyanate, as shown in Fig. 5.15) and a stoichiometric amount of a polyfunctional polyol based on sorbitol, using triethylamine (TEA) as a catalyst (Aranguren and Williams, 1986). 

As an example, the temperature rise for the formation of a polyurethane by reaction of a polymethylenpolyphenyl isocyanate (average functionality = 2.7), with a polyfunctional polyol based on sorbitol, using dibutyltin dilaurate (DBTDL) as a catalyst, is shown in Fig. 5.19 for two different catalyst concentrations (Marciano et al., 1982). 

In this study, the use of a PM polyol as a rubber modifier for a highly crosslinked, polyurethane resin (T = 150 °C) was assessed again in comparison with an oil-based PB polyol. The polyurethane resin matrix was formed from pure MDI and a polyol blend comprising a polyoxypropylene triol, LHT240 (Union Carbide) of equivalent weight 227.6 g-mol"1, and trimethylol propane,... 

Cyclic derivatives of type III include cyclic Mannich bases, such as dihydroben-zoxazines 497, employed as detergents for lubricating oils, - and cyclic urcides 498, precursors of crosslinking agents for fabrics, as well as other cyclic derivatives prepared by conversion of Mannich bases. Macromolecular derivatives of type IV are relatively small in size and have branched (star-shaped) structures they are of considerable importance as, for example, corrosion inhibitors 499, plastics stabilizers 500, - pre-polymers for epoxy-based electrophoretic paints, and polyols in polyurethane synthesis. ... 

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