Elongation is a measure of the extent to which a tape is able to stretch before breaking. Measured in percentages, elongation is a good indicator of how a tape handles and how well it responds to the constant stress of being stretched.
Elongation is a key characteristic to look for when choosing an electrical tape because stretch is an important part of the process of applying the tape in a splicing or phasing task. In electrical applications, the best way to ensure a watertight and secure seal is to stretch the tape as you wrap it around the cable so that when you are finished, the wrapped tape naturally wants to return to form, maintaining a firm grip. The ability to return to form is related to elongation and tends to increase with the grade and quality of tape used. A tape with poor elongation may break easily while being applied, resulting in lost time, wasted tape, and frustration.
High quality electrical tapes typically have higher elongation and return to form much better than lower quality, economy-grade tapes. Using a tape with higher elongation may be more important in critical, high-priority jobs, while one with less elongation is often adequate for general purpose, non-critical applications.