Mechanically Reinforced Silkworm Silk Fiber by Hot Stretching

Silkworm silk, which is obtained from domesticated Bombyx mori (B. mori), can be produced in a large scale. However, the mechanical properties of silkworm silk are inferior to its counterpart, spider dragline silk Therefore, researchers are continuously exploring approaches to reinforce silkworm silk. Herein, we report a facile and scalable hot stretching process to reinforce natural silk fibers obtained from silkworm cocoons. Experimental results show that the obtained hot-stretched silk fibers (HSSFs) retain the chemical components of the original silk fibers while being endowed with increased beta-sheet nanocrystal content and crystalline orientation, leading to enhanced mechanical properties. Significantly, the average modulus of the HSSFs reaches 21.6 +/- 2.8 GPa, which is about twice that of pristine silkworm silk fibers (11.0 +/- 1.7 GPa). Besides, the tensile strength of the HSSFs reaches 0.77 +/- 0.13 GPa, which is also obviously higher than that of the pristine silk (0.56 +/- 0.08 GPa). The results show that the hot stretching treatment is effective and efficient for producing superstiff, strong, and tough silkworm silk fibers. We anticipate this approach may be also effective for reinforcing other natural or artificial polymer fibers or films containing abundant hydrogen bonds.

Automated summary

In this study, a facile and scalable hot stretching process was used to reinforce natural silk fibers. The experimental results showed that the hot-stretched silk fibers retained the chemical components of the original silk fibers while exhibiting enhanced crystalline properties and mechanical properties. This approach could effectively produce super stiff, strong, and tough silk fibers and may be applicable to other fibers or films containing abundant hydrogen bonds.