Diffusion behaviour of the core-sheath structure in E-glass fibres exposed to aqueous HCl

The existence of a characteristic core-sheath morphology in E-glass fibres undergoing acid corrosion is well known. This effect is attributed to the removal of calcium and aluminium ions from the glass structure. Sheath growth measurements indicate that this abstraction involves a two-stage diffusion process, with a room-temperature diffusion coefficient of 1.4×10^–16 m ² sec^–1 initially, slowing to 1.5×10^–17 m² sec^–1 at later times. This two-stage process is related to fibre structure. It is also shown that there is an initial delay, during which the core-sheath structure does not develop.