Polyurethanes polyol starting materials

Table 3.6 Polyisocyanate and polyol starting materials for polyurethanes...

Table 3.6. Polyisocyanate and Polyol Starting Materials for Polyurethanes[2 H28]... 

The properties of polyurethanes crosslinked in this way depend on the starting materials (polyol and diisocyanate) as well as on the additives and on the intensity of the mixing process. 

Thermal degradation of foams is not different from that of the solid polymer, except in that the foam structure imparts superior thermal insulation properties, so that the decomposition of the foam will be slower than that of the solid polymer. Almost every plastic can be produced with a foam structure, but only a few are commercially significant. Of these flexible and rigid polyurethane (PU) foams, those which have urethane links in the polymer chain are the most important. The thermal decomposition products of PU will depend on its composition that can be chemically complex due to the wide range of starting materials and combinations, which can be used to produce them and their required properties. Basically, these involve the reaction between isocyanates, such as toluene 2,4- and 2,6-diisocyanate (TDI) or diphenylmethane 4,3-diisocyanate (MDI), and polyols. If the requirement is for greater heat stability and reduced brittleness, then MDI is favored over TDI. 

Reaction injection moulding is associated with polyurethanes and is different entirely from moulding techniques used commonly for thermoplastics in that the starting materials usually are liquids at room temperature. As the name implies, a chemical reaction takes place in the course of moulding and complex polyurethane items can be made in one step from mixtures comprising polyol, polyisocyanate, and a suitable promoter of the reaction. 

The purpose of this chapter is to describe the polyoxyalkylation of various alcohols and phenols. These compositions are used as polyurethane starting materials (polyols), as surfactants, and as textile aids. The polymerization of various oxiranes to give polyoxyalkylenes has been described in Volume 1 and is not the subject of this chapter. 

Aniline is a starting product for the manufacture of drugs such as acetamino-phen/paracetamol (Tylenol), which is )V-acetyl-4-hydroxyaniline (100). Another commercial product is 4,4 -MDI (methylene diphenyl diisocyanate, 101), which reacts with a polyol (102) to give polyurethanes such as 103. Polyurethanes are used in applications ranging from the foam in upholstery to thermal insulation material in refrigerators. 

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