Temperature Effect on the Mechanical Properties of Liner Materials used for Type IV Hydrogen Storage Tanks

Type IV hydrogen storage tanks play an important role in hydrogen fuel cell vehicles (HFCVs) due to their superiority of lightweight, good corrosion and fatigue resistance. It is planned to be used between -40℃ and 85℃ at which the polymer liner may have a degradation of mechanical properties and buckling collapse. This demand a good performance of liner materials in that temperature range. In this article, the temperature effect on mechanical properties of polyamide 6 (PA6) liner material, including specimens with weld seam was investigated via the stress-strain curve (S-S curve), macroscopic and microscopic morphology. Considering that the mechanical properties will change after the liner molding process, this test takes samples directly from the liner. Results show that the tensile strength and tensile modulus increased by 2.46 times and 10.6 times, respectively, with the decrease of temperature, especially in the range from 50℃ to -90℃. For the elongation at break and work of fracture, they do not monotonously increase with the temperature up. Both of them reduce when the temperature rises from 20°C to 50°C, especially for the work of fracture, decreasing by 63%. The weld seam weakens the mechanical properties, and the elongation at break and work of fracture are more obvious, which are greater than 40% at each temperature. In addition, the SEM images indicate that the morphology of fracture surface at -90°C is different from that at other temperatures which is a sufficient evidence of toughness reducing in low temperature.