Influence of palm oil modified epoxy resin/biscycloaliphatic diepoxide weight ratio on photoinitiated cationic crosslinking and properties of UV-cured coatings

Abstract

Effect of the weight proportion between epoxy resin modified by palm oil (EPO) and a biseyeloaliphatic diepoxide (BCDE) on photoinitiated cationic crosslinking of the system containing EPO, BCDE, triarylsulfonium hexafluoroantimonate salts (TAS) as well as performance of formed coatings have been investigated. The change of TAS and functional groups of the system upon UV-irradiation time was determined quantitatively by IR-spectrometric analysis, using internal standard method. Formation of tridimensional polymer network in the coatings upon UV- exposure was proved directly by evaluation of their gel fraction. It was demonstrated that epoxy group conversion and EPO/BCDE weight ratio relationship had optimal characteristic with the best consumptions of epoxy groups 5.94 and 6.13 mol/kg at 1.2 and 14.4 s of UV-exposure, correspondingly, when EPO/BCDE weight ratio was 20/80, Augmentation of the EPO/BCDE ratio from 20/80 to 60/40 increased flexibility of UV-cured coatings from 10 to 1 mm but decreased their gel fraction from 81 to 59%; the relative hardness of the cured coatings diminished from 0.95 to 0.43 when the EPO/BCDE ratio varied from 10/80 to 40/60.