Techno-mechanical and structural properties of Indian mulberry silkworm fibers: an insight into the structure–property relationship

Non-textile application of silk fiber is the major focus of the present scientific communities. Characteristics, i.e., structural, mechanical, are the key advantages of silk protein to make it promising candidates for its variable application. Keeping this in view, the present investigation has been conducted to understand the structural and mechanical variability of silk breeds, i.e., CSR2 × CSR4 (single hybrid), PM × CSR2 (cross breed) and FC1 × FC2 (double hybrid) for their respective promising non-textile application. It is envisaged that FC1 × FC2 (double hybrid) has the highest tensile strength (431.47 ± 28.46 MPa), Young’s modulus (5.92 ± 0.45 GPa) and β-sheet content (46.62 ± 1.45%). The lowest nano-crystallite size (3.34 ± 0.22) and elongation % (10.85 ± 0.77) were also observed in the FC1 × FC2. Further, significant positive correlation was observed between β-sheet with crystalline % (p *** < 0.001; r = 0.95), crystalline % with tensile strength (p *** < 0.001; r = 0.91) and Young’s modulus with tensile strength (p * < 0.001; r = 0.80). This indicates that the higher the β-sheet content is, the higher the tensile strength and higher crystalline phase of the fiber will be. Crystallite size has a negative correlation with the β-sheet content, crystalline %, tensile strength and Young’s modulus, which shows that the lower the crystallite size, the more the compactness and strength will be.