Ball‐Milled Carbon Black Composite Ink Based on Chlorinated Polypropylene‐Lauric Acid System and Its Positive Temperature Coefficient Characteristics

ABSTRACT Effective thermal management is crucial for flexible wearable electronics. This study presents a high‐performance Positive Temperature Coefficient (PTC) conductive ink using a chlorinated polypropylene (CPP)/lauric acid (LA) matrix and oxidized carbon black (OCB). Spectroscopic analyses (x‐ray photoelectron spectroscopy/fourier‐transform infrared spectroscopy) confirm that hydrogen bonding between oxidized fillers and the matrix optimizes dispersion, synergizing with the sharp solid–liquid phase transition of LA (∼43°C) to trigger rapid resistance changes. Crucially, rheological tests reveal significant shear‐thinning behavior, establishing superior screen‐printing adaptability for flexible substrates. The ink exhibits a PTC intensity spanning three orders of magnitude with reproducible stability over nine thermal cycles. A wearable knee pad prototype successfully demonstrated autonomous overheating protection, highlighting the material's potential for safe, smart clothing and biomedical applications.