Hydrolytic degradation of polysiloxanic coatings on glass fibers

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