<p>This study reports the development and evaluation of a novel hair protectant formulation incorporating hydroxyethyl cellulose (HEC) to enhance thermal stability and improve hair morphology. SEM analysis confirmed that HEC was successfully integrated into the cosmetic-grade system, producing a uniform and continuous film without disrupting component miscibility. FT-IR spectroscopy revealed molecular interactions between the C–O–C ether groups of HEC and the Si–O–Si bonds of silicone-based components, resulting in the formation of a reinforced polymeric network. Thermogravimetric analysis (TGA) substantiated these interactions, demonstrating a marked improvement in thermal resistance, with the HEC-containing formulation retaining 14% more mass at 400&#xa0;°C compared with its HEC-free counterpart, indicative of a synergistic stabilizing effect. Beyond thermal protection, the formulation also enhanced cosmetic performance. SEM images of treated hair confirmed smoother and more uniform surface morphology after heat exposure, consistent with visual observations of increased softness and luster. In addition, hydration testing revealed a 12.7% increase in skin moisture content following application, highlighting the multifunctionality of the product. Collectively, these results establish HEC as an effective additive that improves both the structural and functional properties of hair protectant formulations. The HEC-based system provides superior thermal stability, improved hair surface characteristics, and enhanced moisturizing capability, positioning it as a high-performance solution for advanced hair care applications.</p> Graphical abstract <p></p>