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Chemical Strengthened Glass
StrengthChemically-strengthened glass is five to seven times stronger than untreated glass. With a modulus of rupture of 31,000 p.s.i. (average per ASTM C 158-02) and higher, chemically-strengthened glass can be used in almost any application requiring glass that is stronger and more impact resistant than untreated glass.
Optical QualityChemically-strengthened glass overcomes the distortional characteristics of heat strengthened or “tempered” glass. Chemically-strengthened glass provides optical quality and flatness similar to untreated annealed glass. Treatment temperatures are below the strain point, so glass geometry remains constant, and there is no optical distortion. A uniform compression case depth is produced. Thin glass and complex shapes are easily handled.
Scratch ResistanceChemically-strengthened glass exhibits a scratch resistance much greater than untreated glass. The strengthening process adds case depth to the glass and increases its surface compression, resulting in added strength and protection against scratches and digs.
Break PatternsChemically-strengthened glass exhibits localized break patterns. Chemically-strengthened glass does not dice and should not be used as a safety glass.
Industries Serviced:
- BIOTECH
- ELECTRONICS
- INDUSTRIAL
- PHARMACEUTICAL
- LIGHTING
- INSTRUMENTATION
- OPTICAL
- O.E.M.s
- SECURITY
- LAMINATION
- Any application requiring maximum strength
ProcessGlass is treated in a molten salt causing “ion exchange” of small,soft NA+ ions from the glass with larger, harder K+ ions from the salt. The “stuffing” effect of the large K+ ions forces the surface into compression, producing a closure stress on cracks. Since glass fails in tension only generally originating at a surface, an externally applied tensile stress must first overcome the surface compression before the occurrence of crack growth. It is also more difficult for new cracks to form during handling. This means that glass is effectively stronger; the strength is increased in relation to the magnitude of compressive stress at the crack tip. Since the treatment is carried out at temperatures just below the glass transition temperature, the product does not suffer any deformation or optical distortion.
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Figure 1. Large K+ ions force surface into compression, creating a closure stress on cracks, increasing the strength and making it more difficult for new cracks to form. Furthermore, the surface compression all but eliminates problems of “delayed failure”; i.e. time-dependent weakened under load. |
Technical Characteristics
| Weight |
13# PSF/Inch thickness |
Specific gravity at 70°F
|
2.5 |
| Modules of Elasticity Young's (lb./sq. in.) |
10,600,000 |
Coefficient of Thermal Expansion
|
Per Degree C° 8.6 x 10-6
Per Degree F° 4.8 x 10-6 |
| Poisson's Ratio |
0.22 |
| Thermal Conductivity |
0.55 (BTU/hr)/(ft.°F) |
| Specific Heat at 0°C-100°C, 32°F - 212°F |
0.205 |
Modules of Rupture
Average per ASTM C158 |
31,000 psi |
TestingNaugatuck Glass has all testing done independently at an outside facility. We comply with the two applicable ASTM standards for our field, ASTM C 158-02 and ASTM C 1422-99.
Naugatuck Glass will continue to test for quality and performance, and will update ourself with the latest proven testing methods relating to our field.
ASTM C 158-02ASTM C 158-02 is a flexure test which measures the strength of chemically strengthened glass in p.s.i. through modulus of rupture. Modulus of rupture is found by supporting a 250mm x 38.1mm x 3mm glass sample on its width edge at 200 mm and slowly increasing the stress at the center of the sample.
The sample will flex until failure, the failure point is measured and used to pinpoint the samples modulus of rupture in p.s.i. Copies of a full explanation of the ASTM C 158-02 are available on request.
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