impermeable graphite meaning in English

不渗透石墨
不透性石墨

Test method for impact of impermeable graphite materials
不透性石墨材料冲击试验方法
Test method for flexure strength of impermeable graphite materials
不透性石墨材料抗弯强度试验方法
Test method for compressive strength of impermeable graphite materials
不透性石墨材料抗压强度试验方法
Test method of mechanical properties of impermeable graphite materials - general
不透性石墨材料力学性能试验方法总则