Polyurethane amine additive effects

TURNER ET AL. RIM Polyurethane Elastomers Amine Additive Effects... 

Several types of additives have been found which reduce or eliminate the effects of various catalysts in polyurethane formation. When the catalyst is a simple base, an acid or acid precursor such as an acid chloride will reduce the rate of reaction due to neutralization of the basic catalyst. This is often most desirable, since many of the bases stronger than tertiary amines promote side reactions such as trimerization, carbodiimide formation and allophanate formation. The beneficial effect of acid retarders in a variety of systems was illustrated by Heiss et al. [151], as well as by others. 

Complexes of organotin with amidines have been found to be excellent catalysts for the preparation of polyurethane foams, which do not have the disadvantage of any amine odor and, in addition, delayed onset of the isocyanate-hydroxyl reaction An example of a mercapto-delayed organotin catalyst is 2,2,4,4-tetrakis(alkyl)- l,3,2,4-dithia-stannetane.55 Amine salts of amino acids, tertiary amino acids, and tertiary amino acid-nitrile compositions, have been found to be effective as delayed action catalysts for polyurethane synthesis. They are particularly effective when used in combination with an organometallic compound, such as an organotin. ... 

Thermooxidative degradation, which is more of a problem with polyether polyurethanes, can be inhibited by the addition of antioxidants. Mathur et al. have studied the effectiveness of several commercial antioxidants for stabilizing polyether polyurethanes against UV and thermally induced oxidation. Stabilizers against thermooxidation include hindered phenols, aromatic amines, and phosphites. Commercially available antioxidants have recently been reviewed by Allbee. Replacement of some, or all, of the ether linkages in polyether polyurethanes by silicone has led to a marked improvement in the thermooxidative stability of the resulting polymer. " ... 

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