Preparation And Property Of UV-curable Functionalized Polyurethane Acrylate Film

UV-curable polyurethane acrylate(PUA) coating has broad prospect for application due to its unique properties including excellent abrasion resistance, outstanding flexibility and chemical resistance. In order to open up enormous applications in various fields, it is fundamental to prepare PUA composite coating with enhanced storage modulus, thermal and electrical properties. An effective method to improve these properties is to add nano-fillers into PUA matrix for preparing UV-curable nanocomposite coating. In this work, graphene was selected as nano-filler to add into PUA matrix by solution mixing method and the properties of UV-curable PUA nanocomposite film was characterized. Meanwhile, surface modified graphene was prepared for improving the uniform dispersion of graphene in PUA nanocomposite film.First of all, hydroxyethylacrylate(HEA), polyethylene glycol 2000(PEG-2000), polyvinylpyrrolidone(PVP) and hexadecyl trimethyl ammonium bromide(CTAB) were selected to modify the pristine graphene and the modification results were characterized. In IR spectrum, the edge of graphene sheet contains the remnant active groups. After modification, the interaction occurs between modifier and graphene. The results of SEM and XRD reveal that interlayer spacing of CTAB modified graphene increase maximally; and the CTAB-G sheets contain many exfoliated samples. Therefore, cationic surfactant CTAB has better modification effect on graphene.Four modified graphene HEA-G, PEG-G, PVP-G and CTAB-G were added into the PUA matrix to prepare UV-curable composite film. The XRD results show that the pure PUA and nanocomposite films are all amorphous in nature and have no crystalline regions. The SEM images indicate that the modified graphene CTAB-G is dispersed homogeneously in the PUA matrix. TGA diagrams show that the thermal stabilities of the nanocomposite films are improved, and CTAB-G/PUA nanocomposite film has significant increase in thermal stability.Modified graphene CTAB-G were prepared with different content of CTAB and the effect of the different proportion of CTAB on structure and morphology of graphene were investigated. XRD and SEM images show that when the mass ratio of CTAB to graphene is 2:3, CTAB-G has the largest interlayer spacing and promotes more exfoliation of the graphene layer. In addition, CTAB-G sheets stack loosely. The Raman spectra of CTAB-G and graphene indicate that the addition of CTAB makes the order of graphene decrease, and some defects are produced in the edges of graphene, which is favorable to the dispersion of graphene in polymer. Besides, the sheets’ edges of modified graphene tend to form monolayer or few-layer graphene sheet. The CTAB-G(the mass ratio of CTAB and graphene is 2:3) was incorporated into PUA by UV curing technology with different weight percentages. Infrared spectroscopy results confirm that the disappearances of the C=C bond at about 1636 cm-1(stretching vibration), 1408 cm-1(=CH2) and 810 cm-1(twist motion) after UV curing in the system reflect the complete curing reaction of CTAB-G/PUA nanocomposite films and CTAB-G(0.5 wt %) has no effect on the curing reaction process of PUA. TEM images of graphene/PUA-0.5 and CTAB-G/PUA-0.5 films show that the dispersion of CTAB-G in the polymer is improved. The results of TGA, DMA, and BroadBand Dielectric Spectrometer analyzer of nanocomposite films show that the thermal stabilities, storage modulus, dielectric properties and electrical conductivities of the nanocomposite films are greatly improved. When the mass fraction of CTAB-G is 1%, the initial decomposition temperature Td of CTAB-G/PUA-1.0 increases by 41 °C and Tg increases by 4.44 °C compared with pure PUA film; the storage modulus increases significantly; the relative permittivity is about two times and the electrical conductivity is about 50 times than that of pure PUA film(1 kHz). The nanocomposite film exhibits excellent comprehensive properties.