Enhancing the properties of starch-fiber foaming material by adjusting fiber length: The synergistic effect of macro-micro stress conduction

Starch-fiber based foaming materials are a promising alternative to petroleum-based plastics. The fiber length, as an important factor affecting the process of making foamed materials, was studied in this paper to investigate its influence on slurry rheology and the foaming process, and the mechanism of its influence on mechanical properties was analyzed from the perspective of macro-micro synergistic stress transfer. Different lengths [10 mm (L10), 5 mm (L5), 1 mm (L1), 0.5 mm (L0.5), 0.1 mm (L0.1)] of fibers were used to prepare different composites. The results showed that the increase in fiber length leads to higher slurry viscosity, a more uniform cell structure, and stronger mechanical properties. The L10 composite achieved a tensile strength of 3.25 MPa, which was more than 4 times of the L0.1 composite. Interestingly, the most hydrophobic microstructure was found on the surface of the L0.5 composite, on which the water contact angle reached 130°. Finally, the effect of fiber length on the degradation rate of composites was explored. In summary, this study provides a new idea for the performance analysis of starch-fiber based foaming materials and is helpful in the selection of fiber length in their manufacturing process.