Chemical–physical characterization of ancient paper with functionalized polyamidoamines (PAAs)

Hybrid inorganic–organic treatments, based on amide-amine polymers (PAAs), against thermal oxidation have been prepared on paper dating back to eighteenth century. The polymeric sols are obtained by step-growth Michael addition polymerization and functionalized with siloxane network by sol–gel method. Five types of samples have been prepared changing the molar ratios among the reagents and their concentration. The treated paper samples were subjected to morphological and structural characterization, by using Scanning Electron Microscopy and vibrational spectroscopies (FTIR and Raman), respectively. Static mechanical tests have been carried out on the samples for measuring elastic modulus, ultimate strength, ultimate deformation and energy loss, whereas dynamic-mechanical measurements have been recorded at increasing temperatures to evaluate E′, E″ and tan δ. Finally, Thermo-Gravimetry and Differential Scanning Calorimetry have been carried out in order to study the behaviour of treated samples in temperature with respect the plain paper. The main result is that the siloxane-modified PAA treatment can improve significantly both mechanical and dynamic-mechanical properties, as well as the thermal resistance, without altering the aspect and texture of the original material. In general, the thicker the impregnation, the better the performances of treated paper: the thickest treatment is able to prevent the combustion of paper samples until 500 °C. The treatment is very promising to preserve ancient manuscripts during accidental fire and against the embrittlement due to natural ageing.