UV-light-induced curing of branched epoxy novolac resin for coatings

Abstract

Usually, the processing technology of the thermoset polymers is characterized by the use of the two component formulations, which generally consist of a polymer resin and a hardener. These two component polymer formulations need to be hardened for almost 12 hours at room temperature [1, 2]. Generally, extra heating at 60-160°C is necessary to facilitate the hardening process [3]. The conventional curing process has several relevant disadvantages. Firstly, as the prerequisite condition for acceptable final properties of the produced material, the following thermal treatment is always desirable as a post-curing process [4]. Secondly, there are difficulties with producing large monolith constructions and coating large surfaces that can be sensitive to heating and/or when heating is even impossible [5]. For example, the repair service protective coatings applications for ships in the maritime industry, and for power generators in the energy generation sector [6]. The market of ultraviolet (UV) curable polymers is growing very rapidly, especially in the last decades [7]. This market is anticipated to grow by 7.0% from 2013 to 2019 and is expected to reach USD 7.930

UV-Light Curing of 3D Printing Inks from Vegetable Oils for Stereolithography

“…Another parameter of interest in the case of crosslinked network is the crosslinking density N and the related molecular weight between crosslinks M c . These two parameters were calculated according to the empirical approach adopted by Flory–Rehner [ 50 , 51 , 52 ]. The Table 1 gathers the calculated values of crosslinking density (N) and corresponding molecular weight between the crosslinks for all fully UV-cured resins (cured at 4 s).…”

Cellulose Nanocrystals vs. Cellulose Nanofibers: A Comparative Study of Reinforcing Effects in UV-Cured Vegetable Oil Nanocomposites

“…The UV-light curing process impacts the developed macromolecular chain network, which was revealed by the crosslinking density N and the molecular weight between crosslinks M c that have been calculated according to the Flory–Rehner equation [ 43 ] and corresponds to the empirical approach used by authors before [ 44 ]. Table 3 presents the calculated polymer chain network N and M c values for prepared UV-cured compositions.…”

Multifunctional Gelcoats for Fiber Reinforced Composites

“…From the three different UV regions (UV-A: 400-315 nm; UV-B: 315-280 nm; and UV-C: 280-100 nm [80]), UV-B and UV-C are commonly used to induce photopolymerization [81]. Gaidukovs et al investigated UV-light induced curing of branched epoxy novolac resin for coatings [82]. The cationic photopolymerization of the epoxy novolac resin coatings was initiated by photodecomposition of bis(4-dodecylphenyl) iodonium hexaflurorantimonate.…”

“…In the case of these manufacturing properties, the photocured coatings reached the same hardness as the thermally cured two-component epoxy novolac coatings, presumably due to the dense cross-linking polymer network structure which developed. They stated that UV irradiation times longer than 6 minutes result in the photodegradation of the epoxy novolac resin [82]. This photopolymerization technology of the epoxy novolac resin can be applied to produce protective coatings for diverse applications in power generation and maritime industries, where the thermal curing process is not feasible.…”