High-voltage cables, district heating couplings, battery storage systems, hydrogen tanks, smart grids – energy infrastructure is diverse and complex. All these components have one thing in common: they must meet extreme requirements. Radiation-crosslinked plastics play a key role here. Whether in cable and conduit systems, pipes for district heating networks, housings and connection technology in battery storage systems, or in components for hydrogen and electrolysis plants: thanks to their high temperature resistance, chemical resistance, and durability, radiation-crosslinked components offer decisive advantages.
Improving the Properties of Plastic Components Through Radiation Crosslinking
High-energy, ionizing electron radiation can be used to specifically enhance plastic components such as cables, pipes, fittings, and sleeves. The crosslinking structure created in this way leads to significantly improved resistance to temperature and stress cracking, as well as increased chemical resistance to aggressive media. These properties contribute significantly to operational safety and longevity under demanding conditions. Of particular importance is the improved creep resistance at elevated temperatures and internal pressures. In addition, radiation crosslinking can be used to adjust recovery properties (memory effect) – for example, in shrink sleeves used in district heating networks.
Beta rays from electron accelerators with a maximum energy of 10 mega electron volts (MeV) are typically used for irradiation. During crosslinking, the component is passed under an electron beam in an electron accelerator facility. This results in a homogeneously crosslinked material. The result: significantly improved temperature resistance, chemical resistance, better creep behavior, and increased abrasion resistance – with a sustainably extended service life under the most demanding conditions. Radiation crosslinking is a precisely controllable process. By adjusting the radiation dose, the desired material parameters can be precisely set and reproduced. This makes the technology ideal for high-performance and reliable components in critical energy infrastructure.
Overview of improved properties of radiation-crosslinked plastics
To ensure compliance with the necessary requirements, plastic components in energy infrastructure have been optimized through radiation crosslinking for decades. Of particular importance is the excellent creep behavior – especially for piping systems operating at high temperatures and internal pressures. In principle, four key property improvements can be expected from the radiation crosslinking of plastic components:
- The crosslinking of plastics significantly reduces solubility and swelling caused by solvents. Similarly, radiation crosslinking improves resistance to aggressive media and hydrolysis. This is evident, among other things, in improved stress crack resistance and a significantly reduced loss of strength after exposure to solvents.
- Improved temperature resistance and significantly improved mechanical properties at elevated temperatures. This is relevant for high-voltage cables, district heating couplings, and electrolysis components.
- In addition, significantly slower crack growth can be expected under external point loads.
- An additional advantage of radiation-crosslinked pipes and other flexible components is their improved formability, which facilitates installation – particularly with tight bending radii – and reduces mechanical stress once installed.
Electron beam crosslinking of plastic components in energy infrastructure
Radiation crosslinking is performed after extrusion or molding using fast, high-energy electrons. The crosslinking ensures that the typical disadvantages of not crosslinked thermoplastics – particularly the steep drop-off at high temperatures and under pressure – do not occur.
Even multilayer composite systems, such as those used in pre-insulated pipes, can be radiation-crosslinked in a single process step. The metal components can be penetrated by the radiation, leading to a significant improvement in composite strength – a critical factor for durability and reliability under operating conditions.
Unlike chemically crosslinked plastics (PE-Xa and PE-Xb), there is no risk of residues from crosslinking chemicals in radiation-crosslinked components (PE-Xc). Furthermore, compared to chemical crosslinking processes, physical radiation crosslinking offers very high process reliability and significantly higher production speeds – an advantage for the industrial manufacturing of high-performance energy components.
For a technical comparison of peroxide, silane and radiation crosslinking, see the article on the BGS website.
The Memory Effect of Shrink Products
A particular advantage of radiation crosslinking is evident in shrink products: semi-crystalline materials are imparted with shape memory (memory effect) through the targeted introduction of crosslinking sites. The shape memory arises because radiation crosslinking occurs predominantly in the amorphous regions, where the tangled, long-chain PE molecules are crosslinked. If a product crosslinked in this manner is stretched while hot, this shape can be temporarily "frozen" by cooling it below the crystallite melting temperature. When the product is heated back above the crystallite melting temperature at the user’s site, the original shape at the time of crosslinking is restored. This effect is particularly valuable in applications such as shrink sleeves in district heating networks or corrosion protection systems for metal piping: The sleeve is cold-slid onto the joint, then heat-activated, and permanently seals the connection with a dimensionally stable, leak-proof fit.
Applications of radiation-crosslinked plastics in energy infrastructure
Radiation-crosslinked plastics are used in various areas of energy infrastructure:
1. Cable and line systems
Insulation and sheathing for high- and medium-voltage cables are often radiation-crosslinked. The advantages include higher temperature resistance, lower fire risk, and longer service life. These properties are particularly crucial in smart grids and for connecting renewable energy sources. Heat-shrink tubing and connectors for weatherproof, leak-tight, and mechanically robust connections in power distribution and communication networks also benefit from radiation crosslinking, which enables the production of heat-shrinkable materials.
2. Photovoltaics and Wind Power
Radiation-crosslinked materials in module enclosures, connectors, and cables increase resistance to UV radiation, weathering, and mechanical stress. These properties are particularly indispensable for longevity and operational safety in offshore wind farms or alpine PV systems.
3. District Heating
Shrink products for pre-insulated district heating systems are designed for service lives of over 50 years and are typically installed underground. Here, radiation-crosslinked shrink sleeves and couplings are used, which ensure a permanent and tight connection between pipe segments thanks to the memory effect described above. The shrinkage force is maintained even under overheating conditions, ensuring reliability for decades. As district heating infrastructure expands to reduce CO2 emissions, demand for these components continues to grow.
4. Battery Storage
For stationary energy storage in grids and decentralized systems, radiation-crosslinked plastics are a proven material system. This technology is used here particularly in high-voltage cables to meet stringent requirements for flame retardancy and temperature resistance. Radiation crosslinking enables the production of plastics with flame-retardant and self-extinguishing properties that maintain their safety even under mechanical and thermal stress. This makes the technology a key solution for reliable and long-lasting energy storage systems.
5. Hydrogen / Electrolysis
Power semiconductors and self-regulating heating cables are used for hydrogen infrastructure, including electrolysis plants. Both components are only enabled to meet these extreme requirements through electron beam irradiation. Power semiconductors switch high power during the electrolysis process, and the heating cables ensure that, for example, concrete foundations do not constantly condense or become damp when hydrogen is stored cryogenically.
Radiation-crosslinked components in the supply chain
For plastic components, radiation crosslinking is performed as the final step after molding, during transport to the end user. The advantage of treatment with ionizing radiation is that the products can be used or further processed immediately after a simple release procedure.
Irradiation is typically handled by specialized service providers, as the operation and setup of such facilities are complex. For instance, operators of electron accelerators must meet high structural safety standards and maintain extensive monitoring systems. External service providers offer a clear advantage, which is particularly evident in mass production. Due to their capacity utilization and expertise, their processes are highly automated, ensuring the necessary speed and a high standard of quality in execution.
A product’s passage through the irradiation unit in the facility takes only a few seconds. After irradiation, the release inspection is performed using the barcode and system data. In addition, material tests can be performed depending on the product and the specific application – afterward, the product is ready for immediate use without any waiting time. Ideally, the service provider records and documents every order from goods receipt through the irradiation process to delivery to ensure complete traceability.
Sustainable energy infrastructure thanks to radiation-crosslinked plastics
In the interest of environmental protection, regulatory requirements for plastics are expected to increase in the future. Sustainability and recyclability are therefore a particular focus. Radiation-crosslinked plastic components are extremely durable and can therefore be used for very long periods of over 30 years. At the end of their service life, there are three recycling options: material (physical), raw material (chemical), or energy (thermal) recovery. In material recycling, new plastic components are produced from the secondary raw materials. If material recycling is not feasible or practical, radiation-crosslinked components can easily be sent for raw material or energy recovery.
In a joint, multi-stage research project (was completed by the end of 2023) involving BGS Beta-Gamma-Service, Nylon Polymers, Aalen University, and TU Berlin, new approaches for material recycling of radiation-crosslinked PA 6 and PA 66 have been developed. Thermal and mechanical analyses have shown that the resulting product properties remain at the same level or even improve significantly compared to non-irradiated materials when the materials are irradiated again. This also enables potential savings of up to 15 percent in material costs. Last but not least, recycling reduces the need for virgin material, with a direct impact on the carbon footprint.
In addition to their recyclability, radiation-crosslinked plastic components are particularly impressive in long-term use: They offer high safety, an exceptionally long service life, and are extremely resistant to pressure, temperature, and chemical influences. Thanks to their reliable performance under real-world installation conditions and their versatile applications, they represent a practical and cost-effective solution for energy infrastructure.
Learn more about radiation crosslinking, suitable materials and applications on the BGS website.
