Study On Polymeric Dispersants For Water-based Pigment Dispersions

A series of maleic anhydride-styrene copolymers (SMA) were synthesized by solution sediment polymerization methods, and the SMA synthesized were hydrolysized to make water-soluble polymer SMH. The effects of polymerization temperature and initiator on the molecular weights were investigated. The copolymers were analyzed by Fourier-Transform Infrared spectroscopy(FT-IR), I3C Nuclear Magnetic Resonance Spectroscopy (I3C NMR) and Gel Permeation Chromatography(GPC). Experimentally it is found that increasing the temperature and increasing the rate of initiator decrease the average molecular weight. The FT-IR analysis results indicate that the water soluble polymeric dispersant was the partly hydrolyzed SMA. The data of I3C NMR indicate that the copolymer sequence was "styrene-styrene-maleic anhydride" (SSM). The data of GPC indicate that the number-average molecular is 4934 and the polydispersity is 1.978 with a narrow molecular distribution.The polymer SMH was used as dispersant for organic pigment in water. The dispersity of dispersions were determined by Spectrometer and Scanning Electron Microscopy(SEM). The relation between the polymer characteristics and the dispersity were discussed. It was found that the best dispersity was achieved when the maleic anhydride is 32 percent in the dispersant and the monomer ratio of maleic anhydride to styrene was 1:1. Theproper intrinsic viscosity was between 24-33ml/g for the copolymer used as dispersant. The proper ratio of pigment to dispersant was studied, and the best ratio of pigment to dispersant is 2:1.The dispersity of polymeric dispersant SMH and traditional dispersing agents were compared in this paper. The SEM of dispersions indicate that the polymeric dispersant has the same or better dispersity than the traditional ones. The dispersity of pure pigment dispersion was 55.27. It was better than nonionic surfactant TweenSO. The polymeric dispersant made the pigment microparticle smaller and well-distributed .