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Abstract. By combining a trifunctional urethane acrylate synthesized from a hexamethylene diisocyanate trimer and caprolactone acrylate with a bifunctional urethane acrylate prepared from hydroxyethyl acrylate and isophorone diisocyanate, a new reactive resin mixture was prepared, and trimethylolpropane triacrylate was chosen as the thinner to constitute a novel coating matrix. Different amounts of multi-functionalized carbon nanotubes (CNTs) and graphene oxide (GO) were introduced into the matrix and cured by ultraviolet radiation, producing different coatings. Utilizing the methods of Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, wide angle X-ray diffraction (WAXS) and thermogravimetric analysis (TGA), the chemical structures and physical properties of the coatings were analyzed. A series of ASTM methods, such as pencil hardness classification, RCA abrasion, crosscut adhesion test classification, and chemical resistance rub testing, were applied to investigate the performances of the coatings. It was found that introducing a small amount of carbon nanomaterials can improve the thermal stability, surface hardness, adhesion, abrasive resistance, and chemical resistance performance of the UV-curable coatings. The reasons and mechanisms of the performance improvements are discussed in this work.
Keywords: nanomaterials, polyurethane acrylate, UV-curable coating, carbon nanotube, graphene oxide
1.Introduction
Along with the continually increasing concerns on environmental protection, energy consumption and occupational health and safety, radiation curing technologies, including ultraviolet (UV) and electron beam curing, have received increasing attention in the last several decades. After its invention in the 1960s [1], the UV curing technology is much better known for its 5E characteristics (efficient, enabling, economical, energy saving and environment friendly) and has been widely applied in various industries, including paints, printing, packaging, surface protection and finishing, and device manufacturing in the form of products such as ink, coatings and adhesives [2, 3]. Even in the rising 3D-printing market, the applications of UV-curing technology have exhibited a rapidly growing trend [4]. Currently, UVcurable coatings have the biggest share in the entire UV curing product market [3].
A typical UV-curable formulation consists of reactive resins (oligomers or prepolymers) and reactive thinners, which are also called monomers. Due to the chemical reaction, the thinner is tightly linked to the polymer matrix, thus contributing to the formation of the crosslinked coating film. The power density of the UV radiation by itself is not sufficient to achieve polymerization. For...