Abstract
Graphene carbon nitride (g-C3N4) was successfully prepared by semi-closed pyrolysis and then incorporated into the ultraviolet (UV)-curing system to synthesize different specimens of g-C3N4-hybridized UV-curing (g-C3N4/UV) coatings. The apparent appearance and dispersity g-C3N4 were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The influence of the curing speed and mechanical properties was also tested. The dispersion level of g-C3N4 can be kept less than 1 μm by mechanical mixing. The pencil hardness of composite coatings could be 6H while the adhesion based on glass could be 1 level. The degree of curing of the coating could be obviously improved by the addition of g-C3N4, leading to a 7 percent increase of the gel content. Additionally, the decomposition of hard segments of polyurethane acrylate could be avoided by the use of g-C3N4 resulting in an increasing stability to heat. We found the gel content in an aerobic environment was lower than that in an anaerobic environment. On this basis, the function and mechanism of g-C3N4 was investigated in detail and methods to eliminate the O2 were proposed.
Highlights
IntroductionUV curing technique is becoming more and more important in coating due to its various advantageous characteristics: high machining speed, lower energy consumption and costs, chemical inertness, and environmental friendliness [1,2]
UV curing technique is becoming more and more important in coating due to its various advantageous characteristics: high machining speed, lower energy consumption and costs, chemical inertness, and environmental friendliness [1,2].For application, it is quite necessary that photoinitiators, light stabilizers, and other light activated chemicals to coexist in the same reaction system [3,4]
The pure g-C3 N4 exhibited two obvious positions of diffraction peaks at 13.1◦ and 27.4◦, which can be respectively g-C3N4 exhibited two obvious positions of diffraction peaks at 13.1° and 27.4°, which can be indexed as the (100) and (002) crystal plane. plane corresponds to a nitric distance among respectively indexed as the (100) and (002) crystal plane. plane corresponds to a nitric distance triazine of d = 0.685 nm, and plane indicates a laminar stack with a distance of d = 0.32 nm
Summary
UV curing technique is becoming more and more important in coating due to its various advantageous characteristics: high machining speed, lower energy consumption and costs, chemical inertness, and environmental friendliness [1,2]. An effective method for increasing the photocatalytic efficiency and mechanical properties is to add nanoparticles (1–100 nm), to prepare hybrid UV-curable coatings [7,8] It shows considerable improvement and novel performance compared with traditional composites [9,10]. The contradiction of light initiation and chain termination in the UV curing process can be effectively solved by the development of new high performance UV-curable coatings incorporated with g-C3 N4 , which can play the dual role of photo initiators and light stabilizers, thereby improving the film aging resistance with a high polymerization rate. A possible mechanism of g-C3 N4 accelerating an otherwise kinetically hindered reaction associated with g-C3 N4 /UV composite nanocoatings was discussed
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