Abstract
The exchange of small alkali ions in glass with larger ions from a molten salt bath below Tg produces surface compression in the glass surface, which results in glass strengthening. Two competing processes occur: (1) generation of stress due to “ion stuffing” and (2) relaxation of the same stress due to viscous flow and network ductility. The economics of superior protection of glass products under common challenging environments, generally require a compromise between obtaining greater depths of compression (“case depth”) versus aiming for higher compression magnitudes. Control of process parameters such as bath temperature and composition is essential. Methods of quality control include measuring the modulus of rupture (MOR), surface compression and case depth. The newly instituted ASTM standard C1422–99 classifies chemically strengthened flat glass products on the basis of the surface compression magnitude and the case depth. Aircraft windshields, watch covers, auto- injector glass syringes and high speed glass centrifuge tubes are examples of chemically strengthened glass products well-accepted in the market place. Products such as laminated chemically strengthened architectural glass for hurricane-prone regions and borosilicate glass single-use needleless injectors are being developed.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call