Effect of process conditions on the properties of surface-modified organic pigments encapsulated by UV-curable resins

摘要

Aqueous dispersions of nanoscale organic pigments were successfully prepared via ball milling and ultrasonication. The dispersed organic pigments were encapsulated into UV-curable resins via a mini-emulsion technique. Critical factors that affected the dispersion and encapsulation stability were investigated. The encapsulated organic pigments were characterised with transmission electron microscopy, thermogravimetric analyses, Fourier Transform-infrared spectra and zeta potential. The results clarified that the type of dispersing agent plays an important role in achieving maximal dispersion stability. Encapsulated organic pigments showed greater dispersion stability, and better wettability than the original pigments. Polyester tetra-acrylate oligomer can stabilise the mini-emulsion from diffusion degradation and inhibit phase separation with time. 1,6-Hexandiol dimethacrylate was the monomer of choice for ink-jet printing inks. Furthermore, it was found that monomer/oligomer and pigment/resin ratios were more influential and needed to be optimised. Thermal analysis, ultracentrifuge sedimentation and morphologies provided supporting evidence for the encapsulation of organic pigments into UV-curable resins.