Ruben F A O Torrico1, Samarah V Harb2, Andressa Trentin3, Mayara C Uvida4, Sandra H Pulcinelli5, Celso V Santilli6, Peter Hammer7. 1. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: ro1485.2011@my.bristol.ac.uk. 2. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: samarah.v.h@hotmail.com. 3. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: andressinha.trentin@gmail.com. 4. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: mayarauvida@gmail.com. 5. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: sandrap@iq.unesp.br. 6. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: santilli@iq.unesp.br. 7. São Paulo State University (UNESP), Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address: peter@iq.unesp.br.
Abstract
HYPOTHESIS: The fraction of the silica/siloxane phase is a crucial parameter, which determines the structure and thus the properties of epoxy-siloxane-silica hybrid coatings. A careful adjustment of the colloidal precursor formulation allows tuning the nanostructure towards a highly condensed and cross-linked hybrid nanocomposite, suitable as an efficient anticorrosive coating. EXPERIMENTS: Novel epoxy-siloxane-silica hybrids have been prepared through the curing reaction of poly(bisphenol A-co-epichlorohydrin) (DGEBA) with diethyltriamine (DETA) and (3-glycidoxypropyl)methyltriethoxysilane (GPTMS), followed by hydrolytic condensation of tetraethoxysilane (TEOS) and GPTMS. At a constant proportion of the organic phase, the effects of the varying molar proportions of siloxane (GPTMS) and silica (TEOS) on the film properties have been investigated. FINDINGS: A detailed structural analysis suggests for intermediate TEOS to GPTMS ratios a structure of highly condensed silica-siloxane domains covalently bonded to the embedding epoxy phase. The homogeneous distribution of the quasi-spherical sub-nonmetric silica-siloxane nodes is in agreement with low surface roughness (<5 nm), observed by atomic force microscopy. This dense nanostructure results in high thermal stability (>300 °C), strong adhesion to steel substrate and excellent barrier property in saline solution, with corrosion resistance in the GΩ cm2 range.
HYPOTHESIS: The fraction of the silica/siloxane phase is a crucial parameter, which determines the structure and thus the properties of epoxy-siloxane-silica hybrid coatings. A careful adjustment of the colloidal precursor formulation allows tuning the nanostructure towards a highly condensed and cross-linked hybrid nanocomposite, suitable as an efficient anticorrosive coating. EXPERIMENTS: Novel epoxy-siloxane-silica hybrids have been prepared through the curing reaction of poly(bisphenol A-co-epichlorohydrin) (DGEBA) with diethyltriamine (DETA) and (3-glycidoxypropyl)methyltriethoxysilane (GPTMS), followed by hydrolytic condensation of tetraethoxysilane (TEOS) and GPTMS. At a constant proportion of the organic phase, the effects of the varying molar proportions of siloxane (GPTMS) and silica (TEOS) on the film properties have been investigated. FINDINGS: A detailed structural analysis suggests for intermediate TEOS to GPTMS ratios a structure of highly condensed silica-siloxane domains covalently bonded to the embedding epoxy phase. The homogeneous distribution of the quasi-spherical sub-nonmetric silica-siloxane nodes is in agreement with low surface roughness (<5 nm), observed by atomic force microscopy. This dense nanostructure results in high thermal stability (>300 °C), strong adhesion to steel substrate and excellent barrier property in saline solution, with corrosion resistance in the GΩ cm2 range.