Enhancement of ink-receiving properties of SiO ₂/PVA composite films by using rare earth-modified SiO ₂ particles

For the first time, rare earths were utilized to modify silica (SiO ₂) for improving the ink-receiving properties of silica/PVA (polyvinyl alcohol) composite films which was coated onto PET (polyethylene terephthalate) substrate. Fourier transform infrared spectra, XPS, scanning electron microscope, Brunauer-Emmett-Teller (BET) surface area measurement, contact angle and mechanical strength tests were used to characterize silica and SiO ₂/PVA composite films before and after modification by rare earths. The results indicated that the rare earths can effectively modify silica by increasing the oxygen-containing groups, decreasing the pore size and cumulative volume of pores, and narrowing the pore size distribution. The possible mechanism during rare earth-modification of silica may be due to the breakage of Si-O-C bonds which generates the carbon radicals combined with dissolved oxygen in the solution to form C-O/C-OH bonds. However, the detailed reaction mechanism still needs to be investigated and clarified in the future because of the complexity during the reaction. The characterization of SiO ₂/PVA films illustrates that silica content, compared to rare earth treatment time, has stronger effects on the hydrophilicity enhancement of the films. The tensile strength of SiO ₂/PVA films rapidly increased from 46.8 MPa to 72.6 MPa when increasing the rare earth treatment time from 0 to 10 h. The ink-receiving properties of SiO ₂/PVA films were thoroughly examined which illustrated that modification of SiO ₂ by rare earth up to 10 h can significantly enhance the ink-receiving properties of the composite films in terms of image quality, desiccation time of ink and mechanical strength of films with the optimum SiO ₂/PVA ratio of 0.3 (by weight). Besides, the thermal stability of composite films containing rare earth modified silica was excellent. Therefore, the SiO ₂/PVA composite films containing rare earth-modified silica seem to be promising materials for high-performance applications.