The liner material of the hydrogen storage bottle is the key to the safety of hydrogen barrier
The barrier properties of EVOH copolymer to oxygen, water vapor and carbon dioxide are far beyond other polymer materials. Although PVDC polyvinylidene chloride has excellent barrier properties, it is not suitable for use in gas storage tank liner that is in direct contact with hydrogen because the residual trace chlorine gas will react with hydrogen gas.
EVOH has both the gas barrier properties of PVA and the processability of PE. By adding EVOH, the liner of the hydrogen storage bottle is elastic even at low temperature, ensuring excellent barrier properties. The high gas barrier properties of EVOH are mainly due to high crystallinity and hydrogen bonding of hydroxyl groups. When the ethylene content decreases, the gas barrier property increases; when the ethylene content exceeds 50 mol%, the gas barrier property is seriously impaired.
It should be noted that the gas barrier property decreases with the increase of temperature. For example, when the temperature increases from 20°C to 35°C, the oxygen transmission rate increases by more than 3 times, and when the relative humidity is greater than 30%, water molecules and EVOH in the The effect of the hydroxyl group will lead to a significant decrease in gas barrier properties.