ABSTRACT The growing interest in sustainable polymer systems has motivated the development of multi‐material structures that combine biodegradable and commodity thermoplastics. In fused deposition modeling (FDM), however, achieving reliable adhesion between immiscible polymers typically requires melt blending with compatibilizers or the use of dual‐nozzle printing systems. In this study, we investigate whether controlled thermal management during single‐nozzle FDM can promote interfacial adhesion between poly(lactic acid) (PLA) and polypropylene (PP) without prior blending or compatibilizers. Bilayer tensile specimens were fabricated by sequentially printing PLA as the base layer and PP as the top layer using a single extruder. Interfacial bonding was achieved by tuning processing parameters rather than material modification. G‐code was modified to ensure accurate layer alignment, and the effects of PP nozzle temperature (220°C–250°C), bed temperature (40°C–85°C), and ambient heating (150°C) were systematically studied using a Taguchi design of experiments. Mechanical testing demonstrated that appropriate thermal conditions significantly improve interfacial strength, with optimal adhesion observed at elevated PP extrusion temperature combined with controlled cooling. The results indicate that enhanced adhesion arises from thermally assisted interfacial interdiffusion and physical chain entanglement rather than crystallographic compatibility. This work presents a proof‐of‐concept single‐nozzle FDM approach for producing bilayer PLA–PP structures with improved interfacial performance, providing a foundation for the design of functionally graded or laminated polymer components where different material properties are required on opposing surfaces.
Chatterjee et al. (2026) studied this question.