Polyester polyol, trifunctional

These results have been fit to experimental data obtained for the reaction between a diisocyanate and a trifunctional polyester polyol, catalyzed by dibutyltindilaurate, in our laboratory RIM machine (Figure 2). No phase separation occurs during this reaction. Reaction order, n, activation energy, Ea, and the preexponential factor. A, were taken as adjustable parameters to fit adiabatic temperature rise data. Typical comparison between the experimental and numerical results are shown in Figure 7. The fit is quite satisfactory and gives reasonable values for the fit parameters. Figure 8 shows how fractional conversion of diisocyanate is predicted to vary as a function of time at the centerline and at the mold wall (remember that molecular diffusion has been assumed to be negligible). 

Castor oil is a natural polyol and its glyceryl esters consist of 90-95% ricinoleic acid and 5-10% oleic, linoleic and other fatty acids. Castor oil is approximately 80% trifunctional and 20% difunctional (the average hydroxyl functionality = 2.8 equivalent). Ricinoleic acid in castor oil is treated with ethylene glycol, diethylene glycol and triethylene glycol at 230°C to obtain a series of difunctional polyester polyols. ... 

Products intermediate to the flexible and rigid foams may be obtained from castor oil (a trihydroxyl molecule), synthetic triols of moderate molecular weight and polyesters with a moderate amount of trifunctional hydroxyl compound in the strueture. Current practice, however, is to use tipped polyols of the type used for flexible foams with MDI. Semi-rigid foams are used for such purposes as crash pads, car steering wheels and packaging equipment. 

A multistep reaction, polyaddition, is a polyreaction of at least two bifunctional or higher functional compounds. Polyaddition can result in either linear polymers (thermoplastics) or cross-linked plastics (duroplastics), depending on the specific functionality. Cross-linked products are obtained by means of a reaction of a bifunctional reactant with a trifunctional one. The more polyfunctional the reactant, the more closely meshed the cross-linking will be. That is why the polyols in polyurethane or epoxy resin production are frequently replaced by polyesters and polyethers containing large numbers of OH groups. Polyaddition, like polycondensation, is a multistep reaction. Fig. 4. Important polyadducts include linear and cross-linked polyurethanes as well as epoxy resins (see [2]). 

Polyurethanes are crosslinked in different ways depending on the choice and stoichiometry of reactants and reaction conditions. For example, an isocyanate-terminated trifunctional prepolymer is synthesized from a polyol and diisocyanate. The polyol may be a polyester prepolymer synthesized from a triol or a hydroxyl-terminated polyether. Further polymerization and crosslinking of the isocyanate-terminated prepolymer is achieved by reaction with a diamine... 

---