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Ultrastructures and Mechanics of Annealed Nephila clavipes Major Ampullate Silk
journal contribution
posted on 2020-02-13, 22:45 authored by Thomas
W. Dugger, Sourangsu Sarkar, Sandra M. Correa-Garhwal, Mikhail Zhernenkov, Yugang Zhang, Gitanjali Kolhatkar, Ramya Mohan, Luz Cruz, Aura D. Lubio, Andreas Ruediger, Cheryl Y. Hayashi, Kathryn E. Uhrich, David J. KisailusThe
semicrystalline protein structure and impressive mechanical
properties of major ampullate (MA) spider silk make it a promising
natural alternative to polyacrylonitrile (PAN) fibers for carbon fiber
manufacture. However, when annealed using a similar procedure to carbon
fiber production, the tensile strength and Young’s modulus
of MA silk decrease. Despite this, MA silk fibers annealed at 600
°C remain stronger and tougher than similarly annealed PAN but
have a lower Young’s modulus. Although MA silk and PAN graphitize
to similar extents, annealing disrupts the hydrogen bonding that controls
crystal alignment within MA silk. Consequently, unaligned graphite
crystals form in annealed MA silk, causing it to weaken, while graphite
crystals in PAN maintain alignment along the fiber axis, strengthening
the fibers. These shortcomings of spider silk when annealed provide
insights into the selection and design of future alternative carbon
fiber precursors.