CAEDMON ANALYSIS OF ADSORPTIVE ENERGIES OF GLASS FILAMENTS

Adsorptive energies of glass fiber surfaces were investigated by analy sis of monolayer isotherms using nitrogen and argon as adsorbates at 7 7 K. The CAEDMON algorithm (Computed Adsorptive Energy Distribution in the MONolayer) processed adsorption data to educe changes in glass su rface energetics caused by variations in glass composition, forming co nditions, and thermal treatment. We found the fiber forming process to create surfaces of lower adsorptive potential than that of powdered c ullet. The adsorption energy of fiberglass declined systematically wit h increasing fiber diameter. Thermal treatment activated fiber surface s to nitrogen adsorption. The adsorptive properties of fiber from thre e glasses of varying alkali content were similar. Moisture evolution a nalysis showed the presence of strongly bound molecular water on glass fiber. We hypothesize that the fiber forming process produces surface s passivated to nitrogen adsorption by molecular water strongly bound to silicate structures. The degree of passivation is controlled by the interval during which the fiber surface is at a temperature suitable for chemisorption of ambient moisture. Thick fibers that cool relative ly slowly are therefore passivated to a greater extent than thin fiber s that cool rapidly. Thermal treatment removes the shield of water mol ecules from silicate structures on the surface of fiberglass, increasi ng the charge-quadrupole interaction between the substrate and nitroge n. (C) 1998 Elsevier Science B,V. All rights reserved.