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A filament silk suitable for outer space has been shown to thrive at space temperatures



  Silk
Credit: CC0 Public Domain

Their initial discovery appeared to be a contradiction, since most other polymer fibers become brittle in the cold. After years of work on the problem, the researchers found that the cryogenic toughness of silk is based on nanoscale fibrils. Submicroscopic order and hierarchy allow a silk to withstand temperatures down to -200 ° C. And possibly even lower, making these classic natural luxury fibers ideal for applications in the depths of cool space.

The interdisciplinary team studied the behavior and function of several animal silks cooled to a temperature of -1

96 ° C with liquid nitrogen. The fibers contained spider silk, but the study focused on the thicker and more commercial fibers of the wild silkworm. Antheraea pernyi .

In an article published today in Materials Chemistry Frontiers the team was not only able to show "that," but also "like" silk under conditions in which most materials would increase their toughness become very brittle. In fact, silk seems to contradict the basic understanding of polymer science by not losing in really cold conditions, but gaining quality by becoming both more powerful and more elastic. This study examines the how and explains the why. It turns out that the underlying processes are based on the many nanoscale fibrils that make up the core of a silk fiber.

Consistent with traditional polymer theory, the study assumes that the individual fibrils actually become stiffer as they become colder. The novelty and importance of the study suggests that this stiffening leads to increased friction between the fribrils. This friction in turn increases the crack energy deflection and at the same time resists the slippage of the fibrils. A change in temperature would also affect the attraction between individual silk protein molecules, which in turn affects the core properties of each fibril, which consists of several thousand molecules.

Importantly, research can describe the hardening process in both the micrometer and nanometer range. Scale levels. The team concludes that any crack that breaks through the material is diverted every time it encounters a nanofibril, forcing it to lose more and more energy in the many detours it has to deal with , And so does a silk fiber only when the hundreds of thousands of nanofibrils have stretched first and then slip off and then tear each one individually.

The discovery goes beyond boundaries because it examines a material in conceptually challenging and technological A challenging area that not only covers micrometer and nanoscale, but must also be studied at temperatures well below any freezer. The size of the scales studied ranges from the micrometer size of the fiber over the submicrometer size of a filament bundle to the nanoscale of the fibrils and last but not least to the over-molecular structures and individual molecules. Keeping in mind the latest scientific findings and futuristic applications, it should not be forgotten that silk is not only 100% biological fiber, but also an agricultural product with millennia of research and development. A wide range of novel applications for silks, starting with new materials for the polar regions of the Earth to novel composite materials for light aircraft and kites flying in the stratosphere and mesosphere, to possibly even huge tracks that are spun by robot spiders to catch them astro-junk in space.

Professor Fritz Vollrath of the Zoological Faculty of Oxford University said: "We expect this study to lead to the design and fabrication of new families of tough structural filaments and composites using both natural and silk fibers , inspired filaments for applications in extremely cold conditions such as in space. "

Prof. Zhengzhong Shao of the Macromolecular Science Department of Fudan University, Shanghai "We conclude that the extraordinary mechanical toughness of silk fibers at cryogenic temperatures is due to their highly oriented and oriented, relatively independent and ductile nanofibrillar morphology."

Dr. Juan Guan from Beihang University in Beijing said, "This study provides new insights into our understanding of the structure-property relationships of natural high-performance materials that we hope will result in the production of artificial polymers and composites for low and high temperature impact Applications. "

And dr. Chris Holland of Sheffield University, head of a Europe-wide research consortium for novel, sustainable bio-fibers based on knowledge of natural silk-spinning, said, "Natural silks continue to prove to be gold standard materials for fiber production. The work here shows that not only the chemistry, but also the way silk is spun and, as a result, structured, is the secret of success.

The next steps in research will continue to test the amazing properties. A spin-out company, Spintex Ltd, from Oxford University, funded in part by an EU H2020 scholarship, researches the spinning of silk proteins and focuses on copying the submicron structures of bundled fibrils.

Silk [19659016] Natural silks are environmentally friendly because the animal flings them out of aqueous protein melts at ambient temperatures and low pressure.

  • Many silks are biocompatible and are therefore ideal for use in medical devices. Silk is light and usually very tough. This speaks for low weight applications where a lot of energy needs to be absorbed by the material.
  • All silks are biologically disposable and consist exclusively of natural amino acid building blocks that can easily be integrated into the natural cycle of decay and rebuilding.
  • Last but not least, there is a wealth of information in the silk about protein folding and how nature makes extraordinary polymer structures.

  • Nanomaterials help spiders to spin the hardest substances


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    Oxford University




    Quote :
    A filament suitable for outer space – silk is evidently thriving at space temperatures (2019, October 3)
    retrieved on 3 October 2019
    from https://phys.org/news/2019-10-filament-spacesilk-proven-outer-space.html

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