borosilicate glass tube

high borosilicate glass tube: size: from 3-315mm, and the tubes of 37, 47, 58, 70 for the solar water heater. the high borosilicate glass tube enjoys good heat-proof, anti-rot, mechanical capacity, high working temperature, good technical quality and the favourable price. Main composition: 1) SiO2: 80±0.5% 2) B2O3: 13±0.2% 3) Al2O3: 2.4±0.2% 4) Na2O(+K2O): 4.3±0.2% Chemical properties: 1) Coefficient of mean linear thermal expansion (20°C/300°C): 3.3±0.1 (10-6K-1) 2) Transformation temperature: 525±15°C 3) Working point: 1,260±20°C 4) Softening point: 820±10°C 5) Density at 20°C: 2.23g/cm 6) Hydrolytic resistance at 98°C: ISO719-HGB1 7) Hydrolytic resistance at 121°C: ISO720-HGA1