PEI in Electrolyzer Bipolar Plates

With the global energy structure transitioning to low carbon, green hydrogen energy is becoming a key strategic direction. Hydrogen production from water electrolysis has attracted much attention due to its zero-carbon emission advantage, in which the electrolyzer, as the core equipment, puts high demands on the selection of materials. As an important pressure-bearing and sealing structure of the electrolyzer, the pole frame needs to operate stably for a long period of time in high temperature, high pressure and corrosive environment.

In this context, high-performance plastics or composite materials have become the new trend of replacing metal materials due to their advantages of light weight, corrosion resistance and high strength. Polyetherimide (PEI), as a class of high-performance engineering plastics, has shown great potential in the application of electrolyzer pole frame due to its unique performance.

Functions and Material Challenges of Electrolyzer Bipolar Plates

The electrode frame is a key structural component of the electrolyzer and is mainly responsible for the following functions:

• Supporting and positioning the electrode structure to ensure uniform electric field distribution;
• Realizing electrolyte isolation and avoiding cross-contamination;
• Withstanding high-pressure loads and supporting the entire electrolysis stack;
• Providing a hermetic seal to prevent hydrogen and oxygen leakage.

These functions pose comprehensive performance challenges for the material, including:

• Resistance to high temperatures (>120°C) and high pressures (>30 MPa);
• Resistance to corrosion by strong acids/alkalis;
• Superior creep and fatigue resistance;
• Dimensional stability and low water absorption; and
• High machinability for easy molding of complex structures.

Overview and Core Performance of PEI Materials

1.Material Introduction

PEI (Polyetherimide) is an amorphous thermoplastic polymer with a combination of an aromatic imide backbone and an ether-bonded flexible structure. This molecular design confers excellent thermal stability, mechanical strength and chemical inertness.

2.Thermal Properties and Stability 

• Glass transition temperature (Tg): 217°C
• Continuous use temperature: >170°C
• Short-term heat-resistant temperature: >200°C

Even under long-term high-temperature and high-humidity conditions, there is almost no significant degradation of its physical properties. Even under long term high temperature and high humidity conditions, there is almost no significant degradation of physical properties.

3. Chemical Stability

The imide ring in the molecular structure of PEI provides excellent chemical resistance to strong acids, bases, and oxidizing agents, and is particularly suitable for PEM and acidic hydrogen production environments. In the test, PEI materials can be stabilized in acidic media for more than 3000 hours, far more than other thermoplastics.

4. Mechanical Properties

• Tensile modulus: 3,200 MPa
• Flexural modulus: 3,300 MPa
• High compressive strength, excellent creep and fatigue properties

These properties ensure reliability and long life under high pressure sealing environments.

5. Electrical insulation and ionic cleanliness

PEI has good electrical insulation properties and very low ionic contamination precipitation, which helps to prolong the life of the proton exchange membrane and avoid ionic migration contamination.

Advantages of PEI in Bipolar Plate Applications

1. Seal Reliability and Creep Resistance

SABIC ULTEM™ PEI materials are extremely creep resistant, maintaining structural integrity and sealing under prolonged pressure loads, significantly reducing the risk of leakage. It is particularly well suited to the gas isolation sealing needs of PEM hydrogen production systems.

2. Dimensional stability in hot and humid environments

PEI has a water absorption rate of only about 0.7%, which minimizes dimensional changes under high temperature and high humidity conditions, avoiding structural deformation and sealing failures caused by water absorption and expansion.

3. Advantage of lightweight and integrated design

PEI can realize complex geometric structure and thin-walled parts through injection molding process, which reduces metal processing, lowers the weight of parts, improves modular assembly efficiency, and is conducive to the miniaturization and standardization of hydrogen production equipment.

4. Reliability and service life enhancement

Compared with PPSU, PSU, PES and other materials, PEI shows higher modulus, stronger compression resistance and fatigue life, especially suitable for high-frequency operation, long cycle life requirements of hydrogen production electrolyzer system.

Practical Application Validation and Selection Recommendations

In actual PEM water electrolysis projects, bipolar plates made from PEI (such as ULTEM™ 1000/2300) have shown excellent sealing performance after 1000 cycles of high-temperature and humidity testing, with no structural damage or corrosion observed. Additionally, due to their low contamination characteristics, they significantly extend the lifespan of exchange membranes, reducing maintenance costs.

Selection Recommendations:

• For standard structures and general sealing needs, choose unenhanced PEI (e.g., ULTEM™ 1000).
• For higher modulus and strength requirements, consider glass fiber-reinforced types (e.g., ULTEM™ 2300).
• For special dimensional tolerances or electrical performance needs, custom-modified systems may be considered.

Conclusion

As the hydrogen industry accelerates, material upgrades for electrolyzers have become a critical factor affecting efficiency and reliability. PEI, with its superior comprehensive performance, is gradually replacing traditional metals and lower-performance plastics to become the preferred material for next-generation electrolyzer bipolar plates.

In the future, with continuous optimization of PEI processing technologies and application processes, the lightweight, high-efficiency, and long-life characteristics of electrolyzers will advance further, injecting new momentum into the development of green hydrogen.

For selecting high-performance PEI bipolar plate materials, please contact Shengwen.

Shengwen specializes in high-performance engineering plastic solutions, offering customized PEI-modified materials and injection-molded parts development services. Our PEI materials undergo rigorous screening and performance validation, widely used in advanced manufacturing sectors such as new energy, hydrogen, and semiconductors.

If you are developing electrolyzer projects or seeking alternative bipolar plate materials, feel free to contact us for samples and technical support!