DMA and DSC studies of accelerated aged parchment and vegetable-tanned leather samples

• New parchments and vegetable-tanned leathers were aged under action of humid heat.
• Aged parchments and leathers were studied by DMA and DSC in water and in dry state.
• DMA and DSC have led to close values of denaturation temperature in water.
• A decrease of the denaturation temperature in water with ageing time was observed.
• Under same ageing conditions parchments were more degraded than leathers.

The aim and the novelty of this work was the use of both dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), in water and in dry state, for the investigation of the effects of temperature and relative humidity on degradation of recently manufactured parchments and vegetable-tanned leathers. The materials were subjected to accelerated ageing under action of heat and moisture for progressively increasing time lengths. The studies have proved that accelerated ageing causes a progressive decrease of the temperature of denaturation in water excess, but has no or minor effect on that in dry state. Also, under same ageing conditions parchments undergo a greater degree of deterioration than leathers, as evidenced by a more dramatic change in the DSC peaks (in water) and in the shrinkage curves (DMA). The results can be interpreted as a partial gelatinization occurring in the thermal conditions used for accelerated ageing. The paper presents the advantage of using both techniques, namely that DSC results can assist in interpretation of the DMA curves and that the good correlation of denaturation temperatures obtained by DSC and DMA ascertain these values. Such studies can be useful for understanding the processes that take place on natural ageing of historical parchments and leathers, as well as for establishing proper conditions of their storage.