A novel spectroscopical approach to assess the synthesis and characterization of BPA-free epoxy resins designed for stone conservation

The development of stone conservation products is an active field of research since the achievement of environment-friendly multifunctional products able to ensure, at the same time, long-term key properties such as consolidating and hydrophobic effects, is a hard task. In this sense, novel products derived from Bisphenol A (BPA)-free epoxy resins have become increasingly appealing due to the easy tailoring of their physical, thermal and chemical properties coming from their combination with compatible inorganic precursors and/or their nano- reinforcement [1]. Pursuing this challenge, a cycloaliphatic diol derived from the isobutyric acid, with minor associated health and environmental concerns than phenolic-based ones, was selected to synthetize the corresponding BPA-free epoxy precursors, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CDBO) (Figure 1). To characterize the product, as well as to follow and assess the clean-up and curation process, FT-IR, ATR-FTIR and Raman spectroscopies were employed. H-NMR and 13C-NMR were also used to determine the structure and purity of the obtained epoxy resins. Then, the ratio epoxy-amine used for its thermal cure was optimized with the help of ATR measurements [3]. The thermal behavior of the most promising product, to be exploited as stone conservation material, was studied by TGA and DSC investigations.