Effects of rearing systems and reeling speeds on the structure and properties of forced reeled silk fibers.

With the development of artificial diet-based rearing technology, differences in rearing systems now affect the characteristics of silkworm (Bombyx mori) silk fibers. Forced reeling, a green and non-destructive modification method, has shown significant potential for the preparation of high-performance silk fibers. However, comparative studies on the characteristics of forced reeled silk fibers under different rearing systems are limited. The aim of this study was to compare and analyze the structure and properties of forced reeled silk fibers derived from a mulberry leaf-based rearing system (ML-FRs) and forced reeled silk fibers derived from an artificial diet-based rearing system (AD-FRs) under different reeling speeds. Silkworms reared on artificial diet exhibited better adaptability to forced reeling and AD-FRs exhibited higher strength, stiffness, and thermal stability than ML-FRs. When the reeling speed reached 40 mm/s, the tensile strength and Young's modulus of AD-FRs (712.29 ± 55.69 MPa and 16.10 ± 2.43 GPa, respectively) were higher than those of ML-FRs (649.60 ± 61.90 MPa and 14.45 ± 1.78 GPa, respectively). These results were attributed to the combined effects of differences in the adaptability of silkworms during forced reeling and changes in the secondary structure, crystallinity, and crystal orientation of the forced reeled silk fibers. This study revealed the mechanisms by which rearing systems and reeling speeds affect the structure and mechanical properties of forced reeled silk fibers, providing a theoretical basis and practical guidance for selecting rearing systems and reeling speeds to produce high-strength and high-modulus silk fibers when using forced reeling.