| Abstract: | DSC investigations of various keratins, modified keratins, and keratin model substances have shown that the first of the two endothermic peaks in the temperature range 230 °–255 °C is a microfibrillar helix peak and that the area under the peak represents a measure of the relative helix content of the sample. The peak area of every untreated keratin sample is equal to 100 % and decreases continuously with increasing extension or thermal degradation of the fiber. The relative helix content of annealed keratins depends upon the annealing time and the annealing temperature. Short annealing times at high temperatures, principally, have the same effect as long annealing times, at lower temperatures with one decisive difference: In the first case, the helix peak maximum is shifted to lower temperatures and, in the second case, to higher temperatures. It seems that these shifts, combined with amino acid analyses, are essential to the further understanding of the complicated thermal decomposition of keratins. |
