The influence of cashew nut shell oil (CNO), epoxidized soybean oil (ESO), castor oil (CO), and dioctyl phtalate (DOP) on the photocrosslinking kinetics of UV curable mixtures containing an o-cresol novolac epoxy resin (CNE), a bis-cycloaliphatic diepoxide monomer (BCDE), and a triarylsulfonium salt (TAS) as a cationic photoinitiator has been studied. The formulation with a weight ratio CNE/ BCDE/TAS of 60/40/5 was found to have the highest cure rate and the greatest final conversion of epoxy groups upon UV exposure. The presence of an unsaturated oil or of DOP in the UV curable formulation, at a content ranging from 0.07 to 0.79 mol/kg, was shown to increase the initial polymerization rate of the epoxy groups from 12 up to 31 mol/kg s, and the epoxy conversion after 18 s UV exposure from 80 up to 95%. It was found that the UV cured coatings containing CNO or DOP at concentrations between 0.3 and 0.6 mol/kg and ESO at concentrations between 0.12 and 0.19 mol/kg exhibit the best performance. These results were explained by a number of competitive factors, mainly the effects of the chemical structure and content of the oils and of DOP on the polarity, viscosity, compatibility, and internal filter effect of the UV curable resins, as well as by the characteristics of the tridimensional polymer networks formed upon UV exposure. The materials produced under the optimal conditions determined in this study can be used as high performance decorative and protective coatings and also as adhesives in different sectors of applications.
The influence of the weight ratio of a castor oil modified epoxy resin (CE) and an epoxidiacrylate resin (EDA) on photocrosslinking and properties of the coatings containing these resins, hexandioldiacrylate monomer (HDDA) and photoinitiator Darocur 1173 (D.1173) upon UV‐exposure have been studied. The variation of acrylate groups during the photoinitiated polymerization was evaluated by FTIR analysis. The crosslinking of the UV‐cured coatings was proved by gel fraction and swelling degree determinations. In addition, some of the properties of the UV‐cured coatings such as relative hardness, flexibility, impact resistance, adhesion onto steel plates and gloss have also been examined. It was shown that the increase of the CE/EDA ratio from 10/40 to 40/10 in investigated coatings led to the decrease of the conversion rate of acrylate groups, and significantly changed some properties of the cured coatings after 14.4 s of UV irradiation: Decrease of gel fraction from 96 to 61 %, but improved the flexibility from 10 to 3 mm, impact resistance from 40 to 140 kG.cm, adhesion from 5 to 2 points. The gloss of the coatings remained to be 100 % in all cases. Long hydrocarbon chains of castor oil residue in CE, lower reactivity of double bonds and radicals formed in the chains compared with those of acrylate groups have been attributed to the obtained relationship between the CE/EDA ratio and photocrosslinking, properties of the cured coatings.
The influences of the triarylsulfonium hexafluoroantimonate salts (TAS) content in the range from 1 to 9 % of the total resin and monomer weight on photocrosslinking and properties of UV-cured coatings based on epoxy diacrylate (EDA), hexanediol diacrylate (HDDA), epoxy resin modified by castor oil (CE) and 3,4-epoxycyclohexyl-methyl 3,4epoxycyclohexane carboxylate, a biscycloaliphatic diepoxide (BCDE), have been studied. It was shown that under UVexposure, photoinitiated radical polymerization of acrylate groups of EDA, HDDA and cationic polymerization of epoxy groups of CE, BCDE occurred very fast, leading to formation of interpenetrating polymer networks. The relationship between TAS content and polymerization of epoxy, acrylate groups as well as performance of UV-cured coatings had optimal particularity with highest conversion rate of the groups and properties of the cured coatings containing 5 and 7 % of TAS.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.