Dynamic mechanical analysis (DMA) of new and historical parchments and leathers: Correlations with DSC and XRD

A sort of pure collagen, 22 sorts of new parchments, 35 sorts of old (14th–19th centuries) parchments, 19 sorts of new vegetable tanned leathers and 31 sorts of old (15th–19th centuries) leathers were investigated by DMA technique in tensile mode from room temperature to 260 °C. The obtained results were correlated with those determined by DSC measurements performed in N2 flow in the same temperature range and by XRD. It was pointed out that all collagen-based materials contain a “crystalline” region exhibiting a phase transition (“melting”) in the temperature range 210–260 °C, which is characterized by an endothermic peak in the DSC curve and an abrupt decrease of storage modulus in DMA. Differences in the parameters of this phase transition, related to various deterioration levels, were put in evidence and discussed.