Thermophysical Properties of Pyrex 7740 Glass Over the Temperature Range of –180°C to 475°C

Abstract

Pyrex 7740 glass has been used extensively as a thermal conductivity and thermal diffusivity reference material over the last 40 years. While this material has not been certified as a standard in the U.S., it has been certified for thermal conductivity by BCR in Europe (CRM 039) [1] over the temperature range of –75°C to 195°C. The certified thermal conductivity values from BCR agree with the recommended values established in 1966 by Powell, et al [2] within reasonable uncertainty limits. However, values of thermal diffusivity and specific heat have not been certified. Reliable reference values for specific heat are important in order to calculate thermal diffusivity from thermal conductivity reference values and to compare results obtained by various transient and steady state methods. Reference materials for verification and calibration of thermal diffusivity and conductivity measurements over a broad temperature range are needed in support of materials engineering and research in various fields. The results of measurements of linear thermal expansion by dilatometer, specific heat by DSC and thermal diffusivity measurements by the flash method will be presented for Pyrex 7740. These measurements and the calculated thermal conductivity will be compared to previous literature