08 TECHNICAL INFORMATION | PRODUCT SECTION
Physical properties
Temperature resistance when heated and thermal shock resistance The maximum temperature for short-term use for DURAN® is 500°C. Above a temperature of 525°C the glass begins to soften and above a temperature of 860°C it changes to the liquid state. As it has a very low coefficient of linear expansion ( α = 3.3 x 10 –6 K –1 ), a feature of DURAN® is its high thermal shock resistance up to ΔT = 100K. For a temperature change of 1K, the glass changes by only 3.3 x 10 –6 relative length units, resulting in low levels of mechanical strain were a thermal gradient exists. The thermal shock resistance is influenced wall thickness and product geometry. Temperature resistance at low temperatures DURAN® can be cooled down to the maximum possible negative temperature and is therefore suitable for use with liquid nitrogen (approx. – 196 °C). During use / freezing special attention should be given to the expansion of the content. In general DURAN® products are recommended for use down to –70°C. When working at low temperatures, the effect of any expansion of a DURAN® vessel’s content must be borne in mind. During cooling and thawing ensure that the temperature difference does not exceed 100K. In practice, therefore, stepwise cooling and heating are recommended. When freezing substances in such items as DURAN® bottles or DURAN® test tubes, the container should only be filled to a maximum of 3/4 of its capacity. Moreover, it should be frozen slanted at an angle of 45° (to enlarge the surface area). The minimum service temperature is dependant upon the properties of any screw caps or other components used. For the blue PP screw cap the minimum temperature is – 40°C. Use in the microwave DURAN® laboratory glassware is suitable for use in microwaves. This also applies to plastic coated DURAN® products.
Overview of the physical properties of technical glasses
Description
Linear expansion coefficient α (20 °C / 300 °C) [ 10 – 6 K – 1 ]
Transformation temperature [ °C ]
Density
[ g / cm 3 ]
DURAN® FIOLAX®
3.3 4.9 9.1 6.5
525 565 525 555
2.23 2.34 2.50 2.45
Soda-lime glass
SBW
Optical properties
In the spectral range from about 310 to 2200 nm the absorption of DURAN® is negligibly low. It is clear and colourless. Fairly large layer thicknesses (axial view through pipes) appear slightly yellow/greenish. Amber-coloured DURAN® products are suited to use with light-sensitive substances (see amber colouring of DURAN®). This results in strong absorption in the short-wave region up to approx. 500 nm. In photochemical processes the light transmission of DURAN® in the ultraviolet range is of particular importance. The degree of light transmission in the UV range indicates the ease with which photochemical reactions can be carried out, for example chlorinations and sulfochlorination. The chlorine molecule absorbs light in the range from 280 to 400 nm and thus serves as a transmitter of the radiation energy. Amber colouring of DURAN® laboratory glassware Amber colouring enables storage of light sensitive substances in DURAN® products. Light transmission in the wavelength range between 300 and 500 nm is, in comparison with DURAN® clear glass, < 10%. Accordingly amber DURAN® glass corresponds to USP/EP specifications.
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