Influence of some vegetable oils on the photocrosslinking of coatings based on an o-cresol novolac epoxy resin and a bis-cycloaliphatic diepoxide

Abstract

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.

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

“…It can be seen that absorption bands at 1799 cm -1 (TAS); 748, 791 cm -1 (epoxy groups of BCDE); 911, 2993 cm -1 (total epoxy groups) were sharply decreased; the absorption bands at 3460 cm -1 (hydroxyl groups), 1076 cm -1 (ether groups) significantly increased while absorption band at 1730 cm -1 remained almost unchanged. Therefore, the absorption bands at 1799, 791, 911, 3460 and 1076 cm -1 were used for quantitative evaluation of TAS, epoxy groups of BCDE and total epoxy groups, hydroxyl and ether groups, respectively, by internal standard method, [4][5][6]8] using absorption band at 1730 cm -1 (carboxyl groups) as an internal reference.…”

“…In dependence on the concurrence of the initiation and transfer reaction, the variation of hydroxyl groups during UV-exposure could or could not have an optimal characteristic. [4][5][6][7] Influence of the weight ratio EPO/BCDE on conversion of epoxy groups is demonstrated in figures 3 and 4. It can be noticed that the relationship between the ratio EPO/BCDE and conversion rate or final conversion of epoxy groups had an optimal feature (Fig.…”

“…The preparation of wet coatings of the samples, their UV-irradiation, analysis were realized by using methods and instruments, equipments presented in published works. [4][5][6] 3. RESULTS AND DISCUSSION…”

“…Among them, the addition of bio-renewable epoxidized rubber and vegetables to the photopolymerizable formulations is one of the most efficient method from both production and environment safety points of view. [4][5][6][7] This work focused on investigation of the impact of EPO content in EPO, BCDE mixture on photocrosslinking and performance of photocrosslinked coatings based on EPO, BCDE and TAS.…”

Flexible epoxy novolac coatings: Use of cardanol‐based flexibilizers

“…In this context, epoxy novolacs (EPNs) have become important. Epoxy novolacs are epoxidized novolac resins of higher functionality than the conventional bisphenol‐A‐based liquid epoxy resins . EPNs combine both the properties of good thermal stability (due to phenolic backbone) with the reactivity of the epoxy group.…”