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DURATAN / Thermally prestessed
tubing of borosilicate glass

- Measures available in Duratan - 
Prestressed borosilicate Glass Tubing

DURATAN, prestressed and chemically highly resistant borosilicate glass with low thermal coefficient of expansion:
Using a thermal toughening process, the wall of the tubing can be prestressed which results in glass tubing with high resistance to tension and mechanical shock and with still higher resistance to thermal shock. The familiar high-quality physical and chemical properties of borosilicate glass are thus not changed but complemented.

Advantages at a Glance
Pressure load at the surface 40 - 70 N/mm2
Conturax profile
Some tubing from our product line CONTURAX can also be prestessed (more details upon request).

2 - 3 times higher resistance to tension and mechanical shock compared with glass which is not prestressed
Resistant to temperature shock
Continuous working temperature 350°C
Chemically highly resistant
Scratch resistant
Break-resistant: the glass disintegrates into a meshwork of little blunt-edged pieces which minimizes the risk of injury
Weight reduction of construction elements by reduced wall thickness

Physical and Chemical Data
Coefficient of mean linear thermal expansion a (20°C; 300°C) acc. to DIN ISO 7991 3,3 · 10-6 K-1
Maximum short-time working temperature 350ºC
Densidad r at 25ºC 2,23 g · cm-3
Modulus of elasticity E (Young's modulus) 64 · 103 N · mm-2
Poisson's ratio m 0,20
Thermal conductivity lw at 90 °C  
Temperature for the specific electrical resistance of 108 W · cm (DIN 52326) tk 100 250ºC
Dielectric properties (1 MHz, 25°C)  
       Dielectric constant e 4,6
       Dielectric loss factor (dissipation factor) tan S 37 · 10-4
Refractive index nd (l = 587,6 nm) 1,473
Hydrolytic Class (ISO 719) HGB 1
Acid Class (DIN 12 116) Class S 1
Alkali Class (ISO 695) Class A 2

Mechanical Impact Strength
The mechanical impact strength of hard solid bodies, for example of glass, is determined by a drop test. In the case of luminaries exposed to explosion risk, for example, a ball drop test according to EN50014 standard is carried out on the finished lamp. Based on this standard, Schott-Rohrglas GmbH is able to carry out ball drop tests on the required tubing dimension and provide corresponding results at any time.
The following table shows examples of this kind of result for one tubing diameter with two different wall thicknesses.

Outside diameter Wall thickness Not prestressed breakage at Prestressed breakage at
120 5 mm min. 2 J
max. 6 J
(ave. 4 J)
min. 8 J
max. 14 J
(ave. 13 J)
120 7 mm min. 1 J
max. 4 J
(ave. 3 J)
min. 9J
max. 14 J
(ave. 13J)

Resulting tension profiles in the tubing wall for outer diameter 120 mm with various wall thicknesses.

Tensile Strength

During the prestressing process the surface layers are subjected to compressive stress, whilst the inside of the tu¬bing is under the influence of tensile stress. Breakage is only triggered off by a force of external impact exceeding this pressure load of up to 50 N/mm2 on the surface. The tubing disintegrates into a meshwork of fine little pieces.

Mechanical Impact Strength Measures available

- Flame-proof lighting
- Luminaires with half-shell protection covers
- Tunnel ilumination
- Sight glasses in pipeline construction
- Outdoor lighting
- Architecture
- Decoration

Flame-proof lighting
Measures available
Minimum quantity:
50-100 pcs (depending on measure could be higher)

VIDRASA, Vidrio en Tubo y Varilla, S.A.
C/ Molí d'en Xec, 41 (Nave 20) / Pol. Ind. Molí d'en Xec
08291 Ripollet (Barcelona) / Spain
Tel: +34 933 524 959