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Soda-lime glass, also called soda-lime-silica glass, is the most prevalent type of glass, used for windowpanes, and glass containers (bottles and jars) for beverages, food, and some commodity items. Also Pyrex brand kitchen glassware manufactured since 1998 (when the brand was spun off under World Kitchen) is made of soda-lime glass1 (previously, it was made of better quality, thermal shock resistant borosilicate glass).
Soda-lime glass is prepared by melting the raw materials, such as soda, lime, silica, alumina, and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675°C.2 The temperature is only limited by the quality of the furnace superstructure material and by the glass composition. Green and brown bottles are obtained from raw materials containing iron oxide. For lowering the price of the raw materials, pure chemicals are not used, but relatively inexpensive minerals such as trona, sand, and feldspar. The mix of raw materials is termed batch.
Soda-lime glass is divided technically into glass used for windows, called float glass or flat glass, and glass for containers, called container glass. Both types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition (see table below). Float glass has a higher magnesium oxide and sodium oxide content as compared to container glass, and a lower silica, calcium oxide, and aluminium oxide content.3 From this follows a slightly higher quality of container glass concerning the chemical durability against water (see table), which is required especially for storage of beverages and food.
Typical compositions and properties
The following table lists some physical properties soda-lime glasses. Unless otherwise stated, the glass compositions and many experimentally determined properties are taken from one large study.3 Those values marked in italic font have been interpolated from similar glass compositions (see calculation of glass properties) due to the lack of experimental data.
| Properties | Soda-lime glass for containers |
Soda-lime glass for windows |
|---|---|---|
| Chemical composition, wt% |
74 SiO2, 13 Na2O, 10.5 CaO, 1.3 Al2O3, 0.3 K2O, 0.2 SO3, 0.2 MgO, 0.01 TiO2, 0.04 Fe2O3 |
73 SiO2, 14 Na2O, 9 CaO, 0.15 Al2O3, 0.03 K2O, 4 MgO, 0.02 TiO2, 0.1 Fe2O3 |
| Viscosity log(η, Pa·s) = A + B / (T in °C - To) |
550-1450°C: A = -2.309 B = 3922 To = 291 |
550-1450°C: A = -2.585 B = 4215 To = 263 |
| Glass transition temperature, Tg, °C |
573 | 564 |
| Coefficient of thermal expansion, ppm/K, ~100-300°C |
9 | 9.5 |
| Density at 20°C, g/cm3 |
2.52 | 2.53 |
| Refractive index nD at 20°C |
1.518 | 1.520 |
| Dispersion at 20°C, 104×(nF-nC) |
86.7 | 87.7 |
| Young's modulus at 20°C, GPa |
72 | 74 |
| Shear modulus at 20°C, GPa |
29.8 | 29.8 |
| Liquidus temperature, °C |
1040 | 1000 |
| Heat capacity at 20°C, J/(mol·K) |
49 | 48 |
| Surface tension, at ~1300°C, mJ/m2 |
315 | |
| Chemical durability, Hydrolytic class, after ISO 7194 |
3 | 3...4 |
Coefficient of Restitution (glass sphere vs. glass wall): 0.97 ± 0.015
Thermal Conductivity: 0.9-1.3 W/m.K6
Hardness (Mohs Scale): 6–7citation needed
Knoop Hardness: 585 kg/mm2 + 20citation needed
See also
References
- ^ "10-K filing, WKI Holding Co., Inc." 8 (2004). Retrieved on 2006-10-22. see also: Pyrex website.
- ^ B. H. W. S. de Jong, "Glass"; in "Ullmann's Encyclopedia of Industrial Chemistry"; 5th edition, vol. A12, VCH Publishers, Weinheim, Germany, 1989, ISBN 3-527-20112-5, p 365-432.
- ^ a b "High temperature glass melt property database for process modeling"; Eds.: Thomas P. Seward III and Terese Vascott; The American Ceramic Society, Westerville, Ohio, 2005, ISBN 1-57498-225-7
- ^ International Organization for Standardization, Procedure 719 (1985)
- ^ P. Gondret, et al.: "Bouncing Motion of Spherical Particles in Fluids"; Physics of Fluids, vol. 14, 2002, no. 2, p 643-652.
- ^ Janssen, L.P.B.M., Warmoeskerken, M.M.C.G., 2006. Transport phenomena data companion. Delft: VVSD.
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