*2.1. Materials*

Polypropylene (PP) masterbatches containing multi-walled carbon nanotubes (MWC-NTs) were used for this study. MWCNT loading ratios equal to 15 wt.%, 20 wt.%, and 25 wt.% were purchased from Cheap Tubes Inc (Brattleboro, VT, USA). Those specific ratios were selected based on preliminary Joule heating experiments, previous work demonstrating suitability for ultrasonic welding [36,37] and literature on high content CNT-based polymer films for sensing, self-heating and resistance welding [38,39,44,45].

Glass fiber/polypropylene (GF/PP) adherends were used for ultrasonic welding and disassembly testing. GF/PP IE 6030 unitape PolystrandTM prepregs with a fiber volume fraction of 60%, an areal weight of 461 g/m<sup>2</sup> and a tape thickness of 0.33 mm were purchased from Avient (formerly PolyOne, Englewood, CO, USA).
