Abstract: Use of a glass composition to make a tubular glass body that is adapted to form a glass-metal joint in a tubular solar collector. The composition is a borosilicate glass having a dilatometric chart with a hard segment and a soft segment hysteresis where the soft segment glass transition temperature is less than the hard segment glass transition temperature for a temperature difference ?T higher than 20° C. comprising 5% to 8% Na2O, 0.1% to 3% K2O, 0.1% to 1.5% CaO, 5% to 7.5% Al2O3, 70% to 75% SiO2, and 11.6% to 13.7% B2O3.

Abstract: A glass composition for a tubular glass body used to form a glass-metal joint in a tubular solar collector. Includes a borosilicate glass having a dilatometric chart with a hard segment and a soft- segment hysteresis. The soft segment glass transition temperature is less than the hard-segment glass transition temperature for a temperature difference ?T higher than 20° C. The composition comprises: 5% to 8% Na2O, O, 1% to 3% K20, O, 1% to 1.5% CaO, 5% to 7.5% Al203, 70% to 75% Si02, 11.6% to 13.7% B203, Owing and owing to the choice of the B203 in the range indicated, in combination with the other components, there is a glass transition temperature lower than other borosilicate glasses. The remarkable difference between the soft and hard segments glass transition temperatures make it possible to obtain a tubular glass body particularly suitable for a solar collector.