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The Effect of Catalysts

المؤلف:  A. Ravve

المصدر:  Principles of Polymer Chemistry

الجزء والصفحة:  p471-472

2026-02-09

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The Effect of Catalysts

Catalysts exert strong influence on the rates of reactions of isocyanates with active hydrogen compounds. Most widely used ones are tertiary amines and metal salts, particularly tin compounds. The mechanism of catalysis by tertiary amines is believed to proceed according to the following scheme:

The catalytic activity of the tertiary amines generally parallels their base strength, except when steric hindrance is pronounced. Tin compounds exert much stronger catalytic effects on the reactions than do tertiary amines. This is illustrated in Table 7.7. The mechanism of catalysis by metal salts is believed to operate as follows :

Table7.8 Tm values of some fiber-forming polyurethanes .

Table7.9 The effect of molar ratios on the molecular weight of the product .