3D Printing of Amylopectin‐Based Natural Fiber Composites

Abstract Many ancient Chinese structures, such as portions of the Great Wall, use a unique mortar that derives from glutinous rice (commonly called “sticky rice”). Unlike other types of rice, sticky rice is rich in amylopectin with negligible amylose. Inspired by the long‐term stability of the amylopectin‐based mortars in ancient structures, sticky rice (SR)‐based materials for 3D printing are developed. Heat causes amylopectin gelatinization, during which molecular branches open to form a large network of gel balls. This causes a merger of the granules and improved interaction between the matrix and fillers. To enhance the mechanical properties, cotton fibers are included, ≈11 µm in diameter. During amylopectin gelatinization, secondary fibers emerge from the primary fibers, creating a complex two‐level fiber network. Both the fibers and matrix constitute a 3D printable fiber composite consisting entirely of natural, inexpensive, and scalable components. The processing steps make no use of any non‐natural materials or hazardous chemicals. A systematic design of experiments is conducted to understand the effect of processing parameters on the mechanical properties. Scalability by printing low‐density cellular materials is demonstrated. Finally, it is shown that SR composites are more resilient than common thermoplastic composites when subjected to flame, heat, or ultraviolet light.