# Heating and Strain Sensing Elements Based on Segregated Polyethylene/Carbon Black Composites in Polymer Welded Joints

## TL;DR

This paper explores using carbon black-filled polyethylene composites as heating and strain sensing elements in polymer welded joints.

## Contribution

The study identifies optimal carbon black content for balancing heating and sensing properties in polymer composites during welding.

## Key findings

- Joule heat generation affects polymer crystallinity and conductivity in carbon black composites.
- Lower carbon black content reduces electrical conductivity after welding due to conductive path disruption.
- Higher carbon black content improves conductivity and sensor performance due to closer filler paths.

## Abstract

The development of easy and direct real-time monitoring of welded joint quality instead of surface damage analysis is crucial to improve the quality of industrial products. This work presents the results of high-density polyethylene (HDPE)-based composites with various carbon black (CB) content (from 20 to 30 vol.%) for use as a heating element and strain sensor in electrofusion-welded polymer joints. The pyroresistive heating process was used to determine the effect of generated Joule heat during welding on the structure and sensor properties of polymer–carbon composites. It is shown that the generation of Joule heat depends on the nanocarbon content and affects the crystallinity of the polymer matrix. The partial disruption of the conductive path of carbon black particles was observed and, as a result, a decrease in electrical conductivity for composites with lower CB content after welding was found. For the highest CB amount, conductivity increased, which is caused by smaller particle-to-particle distance for filler paths. Therefore, the best balance between pyroresistive and sensor properties was found.