Unraveling the Depth Dose Effects: Implications for Electron Beam Irradiation in Polymer Extrusion

Abstract

Polymers play a critical role across many industries, from food packaging to healthcare and automotive sectors. However, certain polymers have specific drawbacks that limit their broader application. This necessitates enhanced processing techniques such as electron beam irradiation (EBI), which physically crosslinks polymers and polymer blends to form three dimensional networks. These crosslinked structures are generally considered beneficial because they improve the mechanical strength, thermal stability, durability and many other attributes of the irradiated materials. While EBI offers significant performance benefits, it also presents some challenges. One of these challenges is the so called "depth/dose effect", a phenomenon where electron dosage absorption decreases with depth, leading to non-uniform crosslinking within the material.  This manuscript explores the complexities of the depth/dose effect and its impact on polymer properties, particularly in multilayer films and other high-performance applications. Key factors like material composition, geometric configuration, and process variables (e.g., beam voltage and current) are discussed in relation to their impact on the depth/dose effect. The author then presents several strategies to counteract this effect, including using multi pass irradiation, additive incorporation. Overall, the manuscript provides a detailed understanding of how the depth/dose effect works and what can be done to mitigate it so that polymer extrusion processes subjected to electron beam irradiation yield consistent, high-quality products.