| 摘要 |
Glass is pre-stressed by quenching the hot glass sheet in a cooling liquid which has been heated approximately to its boiling point, the liquid being selected by the value of its heat of vaporization. In the quenching process a gaseous envelope is formed between the glass and liquid which prevents abrupt cooling. The suitability of the quenching medium is determined by the duration of the gaseous phase itself dependent on the heat of vaporization of the quenching liquid. For glasses having a coefficient of expansion 30 x 10-7 liquids containing OH groups and having a heat of vaporization less than 200 cal./g., e.g. propanol, may be used, or for glasses with a coefficient of expansion less than 100 x 10-7 pertanol having a heat of vaporization of 150 cal./g. may be used. The particle size of fragmentation of the glass depends on the cooling liquid used. For fine particle size, liquids having a relatively higher heat of vaporization are used than for glasses fragmenting with a coarse particle size. Several suitable liquids given in the Specification include CCl4, C2Cl4, CHCl3, C6H5Cl, C6H4Cl2, C6H6, C5H11OH, (CH3)3COH, iso-C3H, OH. The gaseous phase may be prolonged by adding sodium dioctyl sulphosuccinate to the liquid and by having mechanical heating means in the cooling bath. |
