Modification of Titania and Iron Oxide Pigments for Application in Photoinitiated Cationic Polymerization of Epoxidized Linseed Oil

ABSTRACT The surface of titania, iron oxide red, iron oxide black, and iron oxide yellow particles was modified by silanization using octadecyltrimethoxysilane in case of all particles. Tetraethoxysilane, octadecyltriethoxysilane, as well as octyltrimethoxysilane were used for surface modification of titania particles only. Furthermore, the surface of titania, iron oxide black, and iron oxide red particles was also modified with a starch laurate protection layer. Moreover, a polymer protection layer was generated in case of titania particles by mini‐emulsion polymerization using the bio‐based methyl 9‐(methacryloyloxy)‐10‐hydroxy octadecanoate/9‐hydroxy‐10‐(methacryloyloxy) octadecanoate isomer mixture alone or together with hexandiol‐1,6‐dimethacrylate as crosslinker. Investigation of the surface modified particles in the photoinitiated cationic polymerization of epoxidized linseed oil (ELO) showed differences in epoxy conversion during ELO polymerization alone or together with bisphenol‐A‐diglycidyl ether (BADGE, weight ratio ELO: comonomer = 2: 1) in the presence of isopropyl thioxanthone (ITX) as sensitizer and bis( t ‐butyl phenyl iodonium) tetrakis( t ‐perfluorobutoxy) aluminate (S2617) as photoinitiator using an UV‐LED emitting at 395 nm for the irradiation during photo‐DSC and real‐time FT‐IR spectroscopic measurements. Crosslinked films were only obtained in case of using surface modified particles in the photoinitiated cationic polymerization of the ELO BADGE mixture. Furthermore, Dynamic Mechanical Analysis (DMA) of crosslinked films made from ELO together with bisphenol‐A‐diglycidyl ether in the absence of pigment and in the presence of iron oxide black pigment gives information regarding differences in the glass transition temperature of these films.