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How does radiation processing cross-link polymers in plastics?

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detector output connected to a measuring circuit — radiation measurement Figure 1: (A) A simple equivalent circuit for the development of a voltage pulse at the output of a detector. R represents the resistance and C the capacitance of the circuit; V(t) is the time (t)-dependent voltage produced. (B) A representative current pulse due to the interaction of a single quantum in the detector. The total charge Q is obtained by integrating the area of the current, i(t), over the collection time, t_c. (C) The resulting voltage pulse that is developed across the circuit of (A) for the case of a long circuit time constant. The amplitude (V_max) of the pulse is equal to the charge Q divided by the capacitance C.

In radiation processing, the cross-linking of polymers in plastics is achieved through chemical reactions induced by high-energy irradiation, typically using electron beams produced by particle accelerators.1

When polymers are exposed to this radiation, the process triggers electronic excitation and ionization of the long-chain molecules that constitute the material. This energy input facilitates the formation of intermolecular bonds—a process known as cross-linking—which effectively links the individual polymer chains together. As a result of this high degree of cross-linking, the material takes on the structural characteristics of a single, giant molecule.2

This technique is widely utilized in industrial applications to enhance the physical properties of plastics, such as increasing their resistance to wear, heat, and chemical corrosion. Common examples include the production of heat-shrinkable packaging, insulation for high-temperature wiring, and the curing of rubber for automobile tires.12