Name: in situ high pressure hydrogen tribological testing of common polymer materials used in the hydrogen delivery infrastructure
Uploaded: 2018-03-31T14:00:00
Description: Watch this Scientific Journal Video about In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure at JoVE.com

This research was performed at the Pacific Northwest National Laboratory (PNNL), which is operated by Battelle Memorial Institute for the Department of Energy (DOE) under Contract No. DE-AC05-76RL01830.

The experiment described here requires the use of hydrogen gas which is odorless, colorless, and thus undetectable by human senses. Hydrogen is highly flammable and burns with a nearly invisible blue flame and can form explosive mixtures in the presence of oxygen. High pressures in excess of 6.9 MPa add additional explosion hazards that must be appropriately planned for in preparation for any testing. This amount of stored energy represents a serious safety hazard and therefore due diligence, planning, and a safety evalu...

<ol>
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Current ex situ techniques for tribological testing of polymer materials require samples to be exposed to high pressure hydrogen which are then depressurized before being tested using a commercial tribometer.15,24,25 The test methodology in this protocol was designed to permit testing of the tribological properties of polymer samples in a high pressure environment in situ. By testing polymer materials such as t...

In the recent years, there has been great interest in hydrogen as a potential zero emission or near-zero emission fuel in vehicles and stationary power sources. Since hydrogen exists as a low density gas at room temperature, most applications use some form of compressed hydrogen for fuel.1,2 A potential drawback of using compressed, high pressure hydrogen gas is incompatibility with many materials found within infrastructure2,3,4 and vehicular applications5 where compatibility issues are combined with repeated pressure and temperature cycling. A pure hydrogen environment is known to damage metal components including certain steels and titanium through different mechanisms including hydride formation, swelling, surface blistering, and embrittlement.2,6,7,8 Non-metallic components such as lead zirconate titanate (PZT) used in piezoelectric ceramics have also proven susceptible to degradation due to hydrogen incompatibility effect such as surface blistering and lead migration.9,10,11,12 While these examples of damage due to hydrogen exposure have been previously studied, the compatibility of polymer components within hydrogen environments has only recently become of interest.13,14,15,16 This is largely a result of metallic components providing structural integrity in nuclear and oil and gas applications whereas the polymer components usually act as barriers or seals.17,18,19,20 As a result, the friction and wear properties of polymer materials within components such as polytetrafluoroethylene (PTFE) valve seats and nitrile butadiene rubber (NBR) O-rings become important factors in their ability to function.
In the case of the hydrogen infrastructure, components such as valves, compressors, and storage tanks contain polymer materials that are in contact with metallic surfaces. The frictional interaction between the polymer and metallic surfaces results in wear of each of the surfaces. The science of the relationship between the friction and wear of two interacting surfaces is known as tribology. Polymers tend to have lower elastic moduli and strength than metallic, therefore the tribological properties of polymer materials differ greatly from metallic materials. As a result, polymer surfaces tend to exhibit greater wear and damage after frictional contact with a metallic surface.21,22 In a hydrogen infrastructure application, rapid pressure and temperature cycling causes repeated interaction between the polymer and metallic surfaces, increasing the likelihood of friction and wear on the polymer component. Quantifying this damage can be challenging ex situ due to possible explosive decompression of the polymer sample after depressurization which may cause non-tribological damage.23 Additionally, many commercial polymer products contain many fillers and additives such as magnesium oxide (MgO) that may interact negatively with hydrogen gas through hydriding, further complicating ex situ analysis of wear in these materials.24,25
Due to the complexity of differentiating between damage to the polymer material caused during depressurization and damage due to tribological wear ex situ, there is a need to directly study the frictional properties of non-metallic materials in situ within a high-pressure hydrogen environment that is likely to exist within the hydrogen delivery infrastructure. In this protocol, we demonstrate a test methodology developed to quantify the friction and wear properties of polymer materials in a high-pressure hydrogen environment utilizing a purpose-built in situ tribometer.26 We also present representative data acquired using the in situ tribometer and ethylene propylene diene monomer (EPDM) rubber, a common polymer sealing and barrier material. The EPDM material for which representative data was generated using the protocol below was purchased in 60.96 cm square sheets with a 0.3175 cm thickness and was reported by the vendor to have a 60A hardness rating.

<table border="0" cellpadding="0" cellspacing="0" width="597">
	<tbody>
		<tr height="79">
			<td height="79" style="height:79px;width:201px;">EPDM Polymer Stock Sheet</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">8525T68</td>
			<td style="width:156px;">24&#34; x 24&#34;, 1/8&#34; Thick</td>
		</tr>
		<tr height="49">
			<td height="49" style="height:49px;width:201px;">Pressure Vessel, Autoclave</td>
			<td style="width:123px;">Fluitron Inc.</td>
			<td style="width:117px;">8308-1788-U</td>
			<td style="width:156px;">5&#34; diameter, 1&#39; height</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:201px;">High Purity Hydrogen Gas</td>
			<td style="width:123px;">Praxair</td>
			<td style="width:117px;">HY4.5</td>
			<td style="width:156px;">Grade 4.5, 5ppm O2, 5 ppm H20</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:201px;">O2 Sensor</td>
			<td style="width:123px;">Advanced Micro Instruments</td>
			<td style="width:117px;">T2</td>
			<td style="width:156px;">0-5ppm min. range, 10,0000ppm max.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:201px;">Pre-purified Argon Gas</td>
			<td style="width:123px;">Oxarc</td>
			<td style="width:117px;">LCCO-HP818</td>
			<td style="width:156px;">High-purity, 99.998%</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Liquid Dishwashing Detergent</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">98365T89</td>
			<td style="width:156px;">32 oz pour bottle, lemon scented</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Mildew Resistant Sponge</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">7309T1</td>
			<td style="width:156px;">6&#34; long x 3 -1/2&#34; Wide x 1&#34; High, yellow</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">PTFE Pipe Thread Sealant Tape</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">4591K12</td>
			<td style="width:156px;">1/2&#34; wide, white color</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:201px;">Gas Tube Fittings</td>
			<td style="width:123px;">Swagelok</td>
			<td style="width:117px;">SS-400-1-4</td>
			<td style="width:156px;">1/4&#34; OD, stainless steel, male NPT threading</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Hammer Driven Die</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">3427A22</td>
			<td style="width:156px;">7/8&#34; Hammer driven hole punch</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Linear Variable Differential Transformer</td>
			<td style="width:123px;">Omega</td>
			<td style="width:117px;">LD320-2.5&#160;</td>
			<td style="width:156px;">2.5mm, AC output, guided w/spring</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Autoclave O-ring Seal</td>
			<td style="width:123px;">Fluitron Inc.</td>
			<td style="width:117px;">A-4511</td>
			<td style="width:156px;">Hastelloy C-276, 5-3/4&#34; OD x 5&#34; ID x 3/8&#34;</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:201px;">Torque Wrench</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">85555A422</td>
			<td style="width:156px;">Adjustable Torque-Limiting Wrench, Quick-Release, 1/2&#34; Square Drive, 50-250 ft.-lbs. Torque</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:201px;">Mallet</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">5939A11</td>
			<td style="width:156px;">Hard and Extra-Hard Rubber Hammer, 2-1/4 lbs.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">iLoad Mini Capacitive Load Sensor</td>
			<td style="width:123px;">Loadstar Sensors</td>
			<td style="width:117px;">MFM-050-050-S*C03</td>
			<td style="width:156px;">50 lb, U Calibration, 0.5% Accuracy, Steel</td>
		</tr>
	</tbody>
</table>

in situ high pressure hydrogen tribological testing of common polymer materials used in the hydrogen delivery infrastructure

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is known about the effects of high pressure hydrogen on the polymer sealing and barrier materials also found within these components. More study is required in order to determine the compatibility of common polymer materials found in the components of the hydrogen fuel delivery infrastructure with high pressure hydrogen. As a result, it is important to consider the changes in physical properties such as friction and wear in situ while the polymer is exposed to high pressure hydrogen. In this protocol, we present a method for testing the friction and wear properties of ethylene propylene diene monomer (EPDM) elastomer samples in a 28 MPa high pressure hydrogen environment using a custom-built in situ pin-on-flat linear reciprocating tribometer. Representative results from this testing are presented which indicate that the coefficient of friction between the EPDM sample coupon and steel counter surface is increased in high pressure hydrogen as compared to the coefficient of friction similarly measured in ambient air.

Using the methodology presented, the coefficient of kinetic friction and wear factor for an elastomeric sample can be measured while in a high-pressure hydrogen environment. The representative data presented in Figure 1 show that in a high-pressure hydrogen environment greater force is required to move EPDM polymer samples under the steel counter surface. Using the relationship between the normal force FN and the frictional force FK the ...

Watch this Scientific Journal Video about In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure at JoVE.com

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

A test methodology for quantifying tribological properties of polymers used in hydrogen infrastructure service is demonstrated and characteristic results for a common elastomer are discussed.

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is ...

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