Development of Biodegradable Composite Yarns With High Mechanical and Thermal Properties via Uniform Distribution of Flax and Polylactic Acid Fibers

ABSTRACT Green composites, based on natural fibers and bio‐based resins, are increasingly utilized in aerospace, automotive, medical and sporting goods due to their lightweight, high strength, and complete biodegradability. However, it remains challenging to develop biodegradable composites that possess excellent mechanical properties and thermal stability simultaneously. The aim of this work was to address the critical challenge of poor interfacial adhesion in flax/PLA composites by developing a novel processing strategy. An innovative solid‐state drawing process was employed to create a unique transcrystalline interface between the flax fibers and the PLA matrix. By optimized blending technology and heat‐sealing processes, the green composite yarns exhibit a tensile strength of 86.2 MPa, a storage modulus of 6.3 GPa, a loss factor of 0.118% and 63.7% biodegradation within 180 days. Compared to previous studies, the tensile strength increased by approximately 22.7%, and the storage modulus increased by approximately 36.1%. The enhanced mechanical and thermal properties of the composite yarn are attributed to the uniform distribution of flax fibers and PLA fibers, which provides higher fiber‐matrix interfacial bonding strength. This work provides a simple and effective strategy for the development of biodegradable composites and demonstrates their potential for use in secondary structural components.