Hydrolytic degradation of polysiloxanic coatings on glass fibers

Aqueous solutions of three silanes: 3-aminopropyltriethoxysilane (APES), 3- aminopropylmethyldiethoxysilane (APDES), and 3-aminopropyldimethylethoxysil ane (APMES), were used to cover glass fibers. The pyrenesulfonyl chloride f luorescent moiety (PSC) was chemically attached to the silanized substrate via the sulfonamide formation when the sulfonyl group of the PSC reacts wit h the amino residues of the coatings. It was studied the silane layer hydro lytic degradation phenomenon (pH = 7) was studied as a function of: i) temp erature, and ii) coating layer type. A hydrolysis reaction mechanism of the polysiloxane bonded onto the glass fibers has been proposed and, the entha lpy change of the process was obtained (3.5 kcal/mol). In addition, it was observed that the greater the silane functionality the faster the hydrolyti c degradation.