Encapsulation Of Organic Pigments With Nano Inorganic Oxides And It's Application In Coatings

Organic pigments are widely used in inks, coatings, plastics, rubbers and so on. There are lots of advantages of organic pigments such as high tinting strength, bright color, broad chromatogram and so on. However, the limited hiding power, poor dispersion ability, and especially the poor weather durability are obviously the obstacles for organic pigments in many applications. Many methods have been explored so far attempting to address these problems, such as encapsulation of polymer, organic pigment coated inorganic oxide, surfactant treatment and so on. In this dissertation, layer-by-layer assembly technique and sol-gel process were adopted to coat the nano silica, silica and titania layers on the surfaces of organic pigments particles. The properties of the modified organic pigments were investigated.In the research of nano silica particles encapsulated organic pigment particles via layer-by-layer assembly technique, firstly poly(sodium 4-styrenesulfonate)(PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) were orderly adsorbed on the surface of the organic pigment particles, then nano silica were adsorbed on the positive surface of the organic pigment particles. The results illustrated that the content of nano silica adsorbed on the organic pigment particles was controlled by number of the polyelectrolyte layers. The thickness of nano silica shell on the organic pigment particles surface could be modulated by adsorbing nano silica layer times. The first layer of nano-silica assembly obviously increased the particle size of organic pigment, resulting a relatively rough surface, an obvious augment in shell thickness and a broad pore size distribution, but the second and the third layers of nano-silica assembly preferred to fill the pores caused by the first layer of silica, causing a relatively smooth surface and slight increases in shell thickness, surface Si content and nanow pore size distribution. The nano-silica particles coated onto the surfaces of organic particles could obviously scatter the UV ray especially after the second and the third layer of silica assembly. The modified organic pigments have a better wettability than the original organic pigment.In the research of silica layer encapsulated organic pigment particles via sol-gel process, the surfaces of the organic pigment were also first orderly modified by PSS and PDADMAC, then coated by silica layer via sol-gel process of tetraethylorthosilicate (TEOS). The results showed that addition of polyvinylpyrrolidone (PVP), pH value, water and TEOS contents had significantinfluence on the morphology of the silica encapsulated organic pigment. Organic pigments coated silica by this approach could scatter UV ray with wavelength less than 270 nm, and this scattering property increased with more silica coated, furthermore, the thermal property of the organic pigment was enhanced.In the research of titania layer encapsulated organic pigment particles by sol-gel process, titania coating successfully encapsulated the organic pigment (Yellow 109) particles by a sol-gel process of titanium n-butoxide (TBOT) using poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) as the bridging agents, which was confirmed by TEM, SEM, XPS and BET analysis. The thickness of the titania coating could be easily adjusted with various TBOT loading in a certain range. X-ray powder diffraction (XRD) analysis indicated that the titania coated on the organic pigment particles was amorphous. TGA results illustrated that titania coating could not improve the thermal stability of the organic pigment but may be beneficial for fire resistance of the organic pigment. UV-Vis spectra showed that titania coating can scatter the UV ray below 270nm, moreover, the scattering of the UV ray increased with increasing thickness of titania coating.The research results of the properties of the modified organic pigment showed that the wettability, resistance to acid and alkali properties, color and weather durability of the inorganic oxide coated Benzidine Yellow G were superior those of their original counterparts. Furthermore, nano silica coated Benzidine Yellow G using layer-by-layer technique has a better wettability and more bright color than the silica and titania coated Benzidine Yellow G using sol-gel process. All these inorganic oxide coatings could improve the weatherability of Benzidine Yellow G...