Uncovering structure–property–function relationships of high-melting palm fats for cleaner material extrusion 3D printing

Material extrusion (MEX) 3D printing, valued for its simplicity and precision, often relies on toxic, non-renewable, and non-biodegradable materials. To address this limitation, this study explores renewable high-melting plant fats as non-toxic, solvent-free, and sustainable alternative inks. Specifically, palm mid fraction (PMF) and palm super stearin (SS), both underutilized by-products of palm oil fractionation, were blended across a range of SS:PMF ratios to systematically modulate the saturated-to-unsaturated fatty acid (SFA:UFA) balance, which governs structure-property-function relationships. Due to their contrasting SFA:UFA ratios, the two fats exhibited distinct thermal behaviors: high-melting triacylglycerols (TAGs) in SS facilitated rapid solidification during deposition, while low-melting TAGs in PMF enabled smooth extrusion. All binary blends exhibited shear-thinning and viscoelastic behavior, supporting their suitability for MEX printing. The optimal blend, comprising 69 wt% SFA and 31 wt% UFA, produced constructs with superior shape fidelity and dimensional accuracy. These constructs retained structural integrity up to 44 °C, indicating suitability for handling at body temperature. Additionally, the constructs maintained oxidative stability over 30 days of ambient storage. Preliminary reuse potential was demonstrated based on reprintability, attributed to the thermoreversible melting-crystallization behavior of the ink. Future work may explore the extended reusability and long-term property retention over multiple reuse cycles. Overall, this study establishes the feasibility of valorizing high-melting palm fat by-products as sustainable and non-toxic inks for MEX 3D printing.