Study on the elasticity of the crystalline lattice of α´-phase polyamide 6 and 11 under hydraulic pressures up to 100 MPa

• Published in: Polymer journal 2023-12, Vol.55 (12), p.1317-1326
• Main Authors: Kasai, Masahiro, Ohyama, Keiko, Nishimura, Shin
• Format: Article
• Language: English
• Subjects: 639/301/923/1028; 639/638/455/303; Anharmonicity; Biomaterials; Bioorganic Chemistry; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Compressibility; Crystal lattices; Electric vehicles; Fuel cell vehicles; Fuel cells; High pressure; Hydraulic pressure; Hydraulics; Hydrogen; Hydrogen bonding; Modulus of elasticity; Molecular chains; Original Article; Polyamide resins; Polymer Sciences; Pressure cells; Pressure reduction; Recovery; Seals (stoppers); Surfaces and Interfaces; Thin Films; Van der Waals forces
• ISSN: 0032-3896; 1349-0540
• DOI: 10.1038/s41428-023-00824-2

Polyamide (PA) is a potential candidate for seals or barriers in systems used to supply high-pressure hydrogen gas to fuel cell vehicles. The elastic behavior of the crystalline lattices of PA6 and PA11 was investigated using a wide-angle X-ray diffraction (WAXD) method while applying hydraulic pressure. A linear decrease in the d -spacing followed by rapid recovery to the initial value after depressurization was observed as the pressure increased. We refer to this behavior as ‘the elasticity of the crystalline lattice’ in this paper. The 002 peaks of PA6 and the 010 peaks of PA11 shifted to larger angles as the pressure increased. The sheets of molecular chains that were bonded by hydrogen bonding composed a layered structure along the [002] (PA6) or [010] (PA11) direction via the van der Waals force. For PA6, the inverse of the linear compressibility was 2.85 times larger than the previously reported uniaxial tensile elastic modulus, which suggested that an anharmonic potential between neighboring molecular chains caused this asymmetric elasticity. This result will be valuable as a way to clarify the mechanism of mechanical fatigue due to cyclic pressurization stress during the hydrogen supply procedure. Polyamide (PA) is a potential candidate for seals or barriers in systems used to supply high-pressure hydrogen gas to fuel cell vehicles. The elasticity of the crystalline lattice of PA6 and PA11 was investigated using a WAXD method and a high-pressure cell while applying hydraulic pressures up to 100 MPa. A linear decrease in the d -spacing for the (002) plane (PA6) and the (010) plane (PA11) followed by rapid recovery to the initial value after depressurization was observed as the pressure increased.