A new catalytic method for crosslinking of silicone polymers

The aim of our work was to develop a gelation process for polymerizing polydimethylsiloxane-alpha,omega-diols for pharmaceutic al purposes. Three different gelling agents has been tried; among them, the prehydrolyzed tetraethoxysilane (TES 40) had the best performance. As initiators, several amines were investigated. The gelling time has been found to be correlated with the basicity, solubility, and diffusibility of the amines. The correlation between the thickness of the oligomer layer and the gelling time has also been investigated. The amount of the remaining initiator after the completion of the network formation has been determined, together with the time needed for its complete removal from the matrix. By using thermogravimetric methods it has been shown that no initiator is left in the matrix. The elastomers obtained by the present method were compared to those obtained by the usual catalysts, resulting in identical properties. The procedure developed is able to produce silicone oligomers for pharmaceutical purposes either in a continous or in a discontinous way. The procedure has several advantages in comparison with the conventional methods, (C) 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1705-1709, 1998.