The SF/HAp nanofibers mats containing 30% HAp nanoparticles showed higher breaking tenacity and extension at break for 1.1688 ± 0.0398 MPa and 6.55 ± 1.95%, respectively.
The reductions in elongation at break and tenacity reach the low level of historic silk when aged for 4 days or more.
Historic silk samples show slightly higher modulus values and much-reduced elongation at break and tenacity in comparison with the reference silk.
Elongation at break and tenacity should be regarded as the most important mechanical properties in conservation science when comparing artificially aged samples with historic silk.
The variables (analytical markers) comprised the amino acid composition, carbonyl index, crystalline index, molar mass from SEC, acidity, Young's modulus, elongation at break and tenacity at break (see Electronic Supplementary Material).
The mechanical results when using thermo-oxidative exposure are fairly similar to the fragile historic silk, especially when balancing the high elastic modulus and the reduced elongation at break and tenacity.
We have already emphasised that break extension and tenacity are the most important properties to achieve for conservation purposes and must have precedence over the elastic modulus.
Thermo-oxidative exposure at higher temperatures (125 °C) reduces break extension and tenacity already from the shortest time exposure with some levelling effects after 28 days.
The mechanical properties of the filaments, particularly tenacity, breaking strain and work of rupture, were reduced as the imposed stress increased, and very severe losses in properties were observed when the stress exceeded the yield stress.
However, these structural changes induced by competitive or combined physical and chemical degradation mechanisms, lead to interconnected effects on the modulus, elongation and tenacity at break that are difficult to control by accelerated ageing procedures, as stated in " Tensile properties".
