An in situ tensile test apparatus for polymers in high pressure hydrogen

Abstract

Degradation of material properties by high-pressure hydrogen is an important factor in determining the safety and reliability of materials used in high-pressure hydrogen storage and delivery. Hydrogen damage mechanisms have a time dependence that is linked to hydrogen outgassing after exposure to the hydrogen atmosphere that makes ex situ measurements of mechanical properties problematic. Designing in situ measurement instruments for high-pressure hydrogen is challenging due to known hydrogen incompatibility with many metals and standard high-power motor materials such as Nd. Here we detail the design and operation of a solenoid based in situ tensile tester under high-pressure hydrogen environments up to 42 MPa (6000 psi). Modulus data from high-density polyethylene samples tested under high-pressure hydrogen at 35 MPa (5000 psi) are also reported as compared to baseline measurements taken in air.

An in situ tribometer for measuring friction and wear of polymers in a high pressure hydrogen environment

“…25,26 To clarify, material degradation of this sort may occur any time the pressure drop is rapid compared to diffusion of hydrogen within the material under study. In previous work by Alvine et al, 36 it has been observed that material properties, such as tensile strength, that change with hydrogen exposure will recover gradually with time as hydrogen diffuses out of the material. 36 For HDPE of cross section 12.7 mm × 12.7 mm (½ in.…”

“…In previous work by Alvine et al, 36 it has been observed that material properties, such as tensile strength, that change with hydrogen exposure will recover gradually with time as hydrogen diffuses out of the material. 36 For HDPE of cross section 12.7 mm × 12.7 mm (½ in. × ½ in.…”

“…[33][34][35] Damaging effects to the base polymer may include bubble or void formation, surface blistering, dilation, changes in modulus and strength, changes in friction and wear, and other changes associated with the absorption of a relatively high amount of hydrogen. 36 Additionally, since the saturation hydrogen concentration in polymers is proportional to the exterior pressure, it is thus expected that the damaging effects are more significant at higher pressures. [28][29][30] Other critical parameters include the rate of depressurization relative to the hydrogen diffusion in the material and temperature cycling effects.…”

“…As noted above, in recent years, there has been an increase in the number of studies of the effects of hydrogen on polymers. This includes investigations of tensile properties of high-density polyethylene (HDPE) 36 and the tribological properties of neat semi-crystalline PTFE [37][38][39] and PTFE composites 17,[40][41][42] in high pressure hydrogen. Additionally, there has been work studying the permeability of hydrogen in polymer materials used in storage and infrastructure applications such as polyethylene, 43,44 polyamide 11, and poly(vinylidene fluoride).…”

PNNL Development and Analysis of Material-Based Hydrogen Storage Systems for the Hydrogen Storage Engineering Center of Excellence

“…While there is an abundance of information on the hydrogen degradation mechanisms in metals and some ceramics, there is still little information in the literature about the detrimental effects of hydrogen on polymers (Castagnet et al 2010, Jaravel et al 2011, Boyer et al 2014, Alvine et al 2014. Absorption in polymers differs from that of absorption in metals (Fukai 2005) in that disassociation of the hydrogen is not expected to occur within the material.…”