Self-diagnostic Coatings for Cultural Heritage: Fluorescent additives.- Characterization, Lightfastness and Influence on a Waterborne Coating’s Yellowing and Plasma Removability of Commercial Pigments

Abstract

Main purpose of this thesis is the identification of different types of photoluminescent additives for the formulation of innovative waterborne self-diagnostic protective coatings which could serve in the field of cultural heritage conservation, enabling to monitor the coating’s health status. The research focuses on the characterization of srtucture and photo-oxidative degradation of some commercial fluorescent products; specifically, dispersions of water-insoluble additives (pigments) have been formulated, after having selected and characterized four products. The selected emitting substances have been shown to be BaMgAl10O17:Mn2+Eu2+ and Y2O2S:Eu2+ as inorganic and Eu3+(TTA)3(TPPO)2 (tris(2-thenoyltrifluoroacetonate)-(bis-triphenylphosphinoxide)europium chelate) and HPQ (2-2’hydroxyphenyl-4(3H)-quinazolinone) as organic pigments. In order to assess their performances in relation to the particle’s size, the pigments have also been ground to nanometric sizes with the bead mill technique. In particular, the influence of external conditions on the emission response, such as the inclusion in an acrylic matrix and a prolonged ultraviolet irradiation, has been investigated for three different particle size distributions. Also the influence of the additives on the photo-oxidative degradation and plasma removability of an acrylic coating have been evaluated. The research is part of the European project PANNA (Plasma and Nano for New Age soft conservation), therefore the removability tests have been carried out by means of a portable atmospheric cold plasma torch developed in the frame of the project. The obtained results and their chemical and physical differences allow one to declare the two organic samples as complementary fluorescent additives, combinable and suitable for various applications in the field of conservation dedicated coatings.