Introduction to electron beam crosslinking of plastic materials

Crosslinking of polymers changes thermoplastic materials into thermosets. This change in molecular structure provides the following benefits:

• Improvement of thermal resistance, heat aging properties and low temperature impact
• Improvement of tensile strenght. modulus, abrasion resistance, creep resistance
• Improvement of heat distortion properties and hot set behavior
• Improvement of chemical resistance and stress crack resistance

In the plastic industry the main crosslinking technologies are peroxide crosslinking and crosslinking by electron beams. With the peroxide technology the crosslinking process can be combined with the shaping process, but it needs elevated temperatures. Electron beam crosslinking is a separate process step, which is carried out at ambient temperature. Special equipment and safety measure are required. On the other hand, the extrusion and shaping process can be optimized independently from the crosslinking step and waste material can be recycled. Also the energy can be modified over the product shape according the crosslinking requirements.

Typical applications of electron beam cured materials:

• Wire and cable isolations
• Water pipes, floor heating pipes, heat shrink tubes
• Shaped articles for electric and electronic applications

A broad variety of plastic materials can be crosslinked by electron beam technology as e.g. polyolefines, polyamide, polyesters and fluoro polymers.

The addition of the coagents TAC and TAICROS improves the crosslinking density in all cases significantly and improves all properties aligned with this. In some cases the coagents are essential to enable crosslinking. The coagents also reduce the radiation dose required for a certain crosslinking degree and by this save radiation time and cost.