Abstract
Objective: In the present work, the possibility of using UV-LED curing processes for the design of “smart” nanocoatings showing enhanced thermal, thermo-mechanical and barrier properties was thoroughly investigated.
Method: A commercially available ethoxylated bisphenol A diacrylate resin, chosen as a model system, was added to 5 wt.% of an organophilic nanoclay (Cloisite 30B) and a photoinitiator (2,4,6-Trimethylbenzoyldiphenyl- phosphineoxide), suitable for the UV-LED curing process. The system was then exposed to UV-LED radiation and the obtained coatings were characterized.
Results: As assessed by infrared spectroscopy and differential scanning calorimetry, a quick exposure (i.e. 5 s) to the UV-LED radiation in dynamic conditions was enough to achieve the completeness of the photocuring reaction. The morphology of the obtained coatings was characterized using X-ray diffraction and scanning electron microscopy: in particular, a clear increase in the interlayer distance was observed, hence indicating the occurrence of intercalation phenomena of the nanofiller into the curable resin. Furthermore, the good interactions taking place between the clay nanoplatelets and the polymer network were responsible for: i) an increase of the glass transition values of the polymer network, ii) enhanced thermal and thermo-oxidative stability of the nanocoatings and iii) improved barrier properties towards oxygen diffusion.
Conclusion: The UV-LED curing process was found very suitable for obtaining nanostructured coatings showing decreased oxygen permeability, as well as improved thermal and thermo-mechanical features.
Keywords: UV-LED technology, radical photo-induced polymerization, acrylic monomers, phyllosilicate, thermal properties, barrier properties.
Graphical Abstract
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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