CAEDMON analysis of adsorptive energies of glass filaments

Adsorptive energies of glass fiber surfaces were investigated by analysis of monolayer isotherms using nitrogen and argon as adsorbates at 77 K. The CAEDMON algorithm (Computed Adsorptive Energy Distribution in the MONolayer) processed adsorption data to educe changes in glass surface energetics caused by variations in glass composition, forming conditions, and thermal treatment. We found the fiber forming process to create surfaces of lower adsorptive potential than that of powdered cullet. The adsorption energy of fiberglass declined systematically with increasing fiber diameter. Thermal treatment activated fiber surfaces to nitrogen adsorption. The adsorptive properties of fiber from three glasses of varying alkali content were similar. Moisture evolution analysis showed the presence of strongly bound molecular water on glass fiber. We hypothesize that the fiber forming process produces surfaces 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 relatively slowly are therefore passivated to a greater extent than thin fibers that cool rapidly. Thermal treatment removes the shield of water molecules from silicate structures on the surface of fiberglass, increasing the charge–quadrupole interaction between the substrate and nitrogen.