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DUROBAX / Physical and Chemical Properties - Introduction | Tubes | Properties -
Borosilicate 4.9

Physical Data
Mean coefficient of linear expansion a20/300 acc. to DIN 52328 4.9 · 10-6 K-1
Transformation temperature Tg 565 ºC
Temperature fixed points at viscosity h in dPa · s:
               1013 upper annealing point 565 ºC
               107.6 softening point 785 ºC
               104 working point 1165 ºC
Density r 2.34 g · cm-3

Resistance to Thermal Shock
Resistance to thermal shock is not an exact, by defined physical quantity (for more details see ISO 718); it depends on the measuring method, the shape, the wall thickness and the surface and end properties of the glass object in question. Rapid temperature changes cause high temporary stress in the glass, meaning that rapid cooling processes are very dangerous, since in this case a thin outer layer of the glass is placed under tensile stress over the still hot inner core. Glass is much more susceptible to tensile stress than to compressive stress.
The following graph shows the resistance to thermal shock of the tubes Duran, Durobax, Fiolax Clear, Fiolax Amber, Illax and AR-Glas:


Chemical Composition (main components in approx. weight %)
SiO2 B2O3 Al2O3 Na2O BaO CaO
75 10,5 5 7 << 1 1,5

Chemical Data
Hydrolytic Class (ISO 719) HGB 1
      according Ph. Eur. Tipo I
      according USP 25 Tipo I
Acid Class (DIN 12 116) Clase S 1
Alkali Class (ISO 695) Clase A 2

Durobax Transmission
Longitud de onda: Wavelength

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