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DURAN / Physical and Chemical Prop. - Introduction | Tubing | Capillary | Rod | Properties -  Duran Catalogue
Borosilicate 3.3 Glass

Physical Data
Mean coefficient of linear expansion a 20/300 acc. to DIN 52328 3.3 · 10-6 K-1
Transformation temperature Tg 525 ºC
Temperature fixed points at viscosity h in dPa · s:
               1013 annealing point 560 ºC
               107.6 softening point 825 ºC
               104 working point 1260 ºC
Maximum short-time working temperature 500 ºC
Density r 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 ºC 1.2 W · m-1 · K-1
Temperature for the specific electrical resistance of 108 W · cm tk 100 250 ºC
Logarithm of the electric volume resistance (W · cm)
      at 250 ºC 8
      at 350 ºC 6.5
Dielectric properties (1MHz, 25 ºC)
Dielectric figure e 4,6
Dielectric loss factor tan d 37 · 10-4
Refractive index nd (l = 587.6 nm) 1.473
Stress-optical constant (DIN 52314) K 4.0 · 10-6 mm2 · N-1

Pressure Resistance of Duran Tubing and Capillary
Calculation of pressure resistance (p) for a given Wall Thickness (Ep) and a given Outside Diameter (De): Pressure calculation De = Outside Diameter, in mm
Ep = Wall Thickness, in mm
p = Pressure Resistance in bar
R/S = Resistance Parameter in N · mm-2
Calculation of the Wall Thickness (Ep) at a given pressure resistance (p) and Outside Diameter (De): Pressure calculation

Resistance parameter for DURAN Borosilicate Glass 3.3: K/S = 7 N · mm-2, as per DIN EN ISO 1595 Standard: Pressure equipment made from Borosilicate Glass 3.3: General rules for design, manufacture and testing.
Pressure resistance (p) is also influenced by the following:
- Difference in temperature between inside and outside wall - Observance of Conditions of installation as per Pressure Vessel Regulations
- Surface Quality - Tubing Length
- End Finish

Resistance to Thermal Shock
According to DIN ISO 718, the resistance to thermal shock is the difference in temperature between the hot test sample and the cold water bath (room temperature) at which 50 % of all test samples show a tendency to crack when quickly immersed. Resistance to thermal shock of tubing, capillary and rod is dependent on the wall thickness, the shape and size of the quenched area, the state of the surface, the stress which may be present and the end finish. Fast, uneven heating or cooling can easily lead to breakage as a result of tensile strength. It is recommended not to exceed a temperature difference of 120 ºC. For large wall thicknesses, this temperature is limited to lower values. Listed below are some measured values to illustrate the resistance to thermal shock of DURAN Borosilicate Glass 3.3 tubing and rod. These should be used only as reference values as considerable differences between tubing/rod of the same dimensions are possible.

Tubes OD   50.5 / WT 5.00 mm: 220 ºC Rod Diam. 24.0 mm: 140 ºC
  OD 133.0 / WT 7.00 mm: 180 ºC    
  OD 120.0 / WT 8.00 mm: 180 ºC    

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 Na2O + K2O Al2O3
81 13 4 2

Chemical Data
Hydrolytic Class (ISO 719) HGB 1
Acid Class (DIN 12 116) S 1
Alkali Class (ISO 695) A 2

DURAN Borosilicate Glass 3.3 is highly resistant to water, neutral and acid solutions, concentrated acids and acid mixtures, and to chorine, bromine, iodine and organic substances. The chemical resistance of this glass is superior to that of most metals and other materials, even when exposed to long processing periods and temperatures above 100 ºC. A slight release of mainly monovalent ions takes place after exposure of the glass to water or acids. A very thin layer of impervious silica gel is subsequently formed on the surface of the glass, which in turn slows clown further attack. At higher temperatures and in more concentrated forms the glass surface is subject to increased attack by hydrofluoric acid, hot phosphoric acid and alkaline solutions.

Transmission %)
Duran Transmission
Wavelength (nm)

Hints on Processing
The excellent properties of DURAN tubing, capillary and rod provide for good workability when forming and cutting the glass with the normal techniques for technical glass. To eliminate temporary stress as a result of the working process, the glass should be well heated to a maximum temperature of 550 ºC and kept at this level for a maximum of 30 minutes; for a thinner wall only a fraction of this period is necessary. In order not to affect the chemical stability of the glass, annealing time should be kept as short as possible. We recommend the annealing temperatures given in the table below:

Annealing Schedule
Wall Thickness,
in mm
Temperature Range
550 to 480 ºC 480 to 400 ºC 400 to 20 ºC
3 12 ºC/min 24 ºC/min up to 480 ºC/min
6 3 ºC/min 6 ºC/min up to 120 ºC/min
12 0.8 ºC/min 1.6 ºC/min up to 32 ºC/min

If an article needs to be annealed several times, the sum of all annealing periods at 550 ºC should not exceed 2 hours. DURAN products can be fused stress-free with borosilicate glasses of the same type and can be processed and annealed at the same temperatures. Printing on DURAN tubing, capillary and rod can be done with silver copper diffusion and screen-printing dyes.

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