appreciable adj. 可評估的；可感知的；相當可觀(guān)的resistance to thermal impact vt. 影響；撞擊；沖突；壓緊vi. 沖擊；產(chǎn)生影響n. 影響；效果；碰撞；沖擊力

 and higher temperatures, also has excellent resistance to

chemical attack.

In this glass structure, the first to carry the Pyrex trademark, some of the SiO² is replaced by boric oxide.

Borosilicate glass has a low coefficient of thermal expansion

and is, thus, suited for telescope mirrors and other precision

parts. Also, because this glass can withstand thermal shock, it is used for oven and laboratory ware, headlamp ['hedlæmp] n. 桅燈；照明燈；車(chē)前燈lenses, and boiler gage glasses. Most borosilicate glasses have better resistance to acids than do soda-lime堿石灰 glasses, but poor resistance to alkalis'ælkəlai] n. 堿；可溶性無(wú)機鹽adj. 堿性的. Glass fibers used in reinforcing plastic compounds ['kɔmpaund, kəm'paund] n. 化合物；混合物；復合詞are a modified borosilicate glass.

Chemical Composition
SiO2 = 80%
B2O3 = 13%
Na2O +K2O= 4.3%
Al2O3 = 2.4%

·         Physical Properties
Coefficient of expansion (20°C–300°C) 3.3 x 10-6 K-1
Density 2.23g/cm3
Refractive index折射率： (Sodium D line) 1.474
Dielectric [,daii'lektrik] adj. 非傳導性的；誘電性的n. 電介質(zhì)；絕緣體constant 電容率(1MHz, 20°C) 4.6
Specific heat比熱 (20°C) 750J/kg°C
導熱系數 (20°C) 1.14W/m°C
Poisson’s Ratio['reiʃiəu, -ʃəu] n. 比率，比例地基應力和變形泊松比(25°C – 400°C) 0.2
Young’s Modulus['mɔdjuləs, -dʒu-]n. 模數；系數

彈性模量，楊氏系數 (25°C) 6400 kg/mm2
Optical Information
Refractive index (Sodium D line) = 1.474
Visible light transmission, 透光率2mm thick glass = 92%
Visible light transmission, 可見(jiàn)光穿透率5mm thick glass = 91%
Critical Temperatures
150°C - When working above this temperature care should be taken to heat and cool Borosilicate glass in a slow and