Fibroin degradation - Critical evaluation of conventional analytical methods

Due to their practical importance and widespread application in the studies of polymer degradation, the analytical methods: viscometry, colour and mass change, pH, mechanical strength were selected in this work so as to provide a macroscopic view of silk condition. The aim of the current work is to critically discuss the results obtained by these methods and confront them with the silk structure and degradation mechanism. They were differentiated with several criteria such as chemical (structural) information they bear, sensitivity to the changes induced by environment and their discriminative power. The results show that tensile strength before colour change and viscosity is the most sensitive method to measure silk degradation at various conditions. Significant colour change is typical of oxygen rich degradation atmosphere and was correlated with oxidation products of fibroin. Viscosity was shown to be hard to interpret in terms of mere changes of molecular mass as the most profound effects were observed in oxygen-rich conditions. Detailed research showed that oxygen plays an important role in silk degradation but it is only when combined with closed and humid conditions that results in catastrophic change.