BPA-free Epoxy–Silica Hybrid Materials of Natural Origin for Stone Conservation: Inhibition Potential Against Biocolonization

In this work, epoxy–silica hybrids based on a BPAfree bio-based cycloaliphatic diol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), were tuned and tested as multifunctional products with consolidating, water-repellent and biocide capacity to be used for stone recovery. For that purpose, sol-gel technology was applied to carry out the epoxy hardening reactions, via triethylenetetramine (TETA), in the presence of 3- glycidyloxypropyl)trimethoxysilane (GPTMS) and octyltriethoxysilane (OcTES), as silica-forming additives to acquire the flexibility and hydrophobic base requirements [1]. Then, the formulations were enriched, using different synthetic strategies (i.e., as such ionic liquids, essential oils and nanoparticles), and checked to gain an inhibition potential against biocolonization while keeping the main properties unchanged. Thus, the effect imparted on the hybrid network by various blends of dimethyloctadecyl[3(trimethoxysilyl)propyl] ammonium chloride, tetradecyl phosphonium, thyme oil encapsulated in mesoporous SiO2 nanoparticles and cerium-doped TiO2 nanoparticles was investigated by a combination of Scanning Electron Microscopy/Energy-Dispersive X-ray spectroscopy (SEM-EDS), Fourier Transform Infrared (FTIR) and Attenuated Total Reflection Infrared (ATR-FTIR) measurements. Moreover, the thermal, hydrophobic, and chromatic properties of the hybrids were determined by thermogravimetry/differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle, and color measurements. Furthermore, the antimicrobial growth inhibition capacity was studied by agar disk-diffusion method using sowing strains of Micrococcus luteus, and Anthrobacter spp. bacteria and, the most promising formulations were final tested on lithic samples by accelerated aging tests in acidic chambers. References [1] O. Gomez-Laserna, P. Irizar, G. Lando, L. Kortazar, A. Irto, L. Ruiz-Rubio, I. Martinez-Arkarazo, P. Cardiano, M. A. Olazabal, Progress in Organic Coatings, 151 (2021) 106028.