The Surface Modification Of Nano-Powder And Solvent Effect In The Process

In order to obtain high performance of polymer nanocomposites, the surface modification of nano-powder is very important. The macromolecular coupling agent contains chemical groups which can bond on the surface of nano powder and flexible long chain which can be compatible with the polymer matrix. So we use the macromolecular modifier to modify nano powder, it can improve the dispersion of powder in polymer matrix, and the performance of polymer nanocomposites was improved. However, there are many factors, which can affect the dispersion properties of powders, in the process of surface modification of nano powder. In this paper, the effects of solvent and the structure of macromolecular in the modification processs were studied.1. A macromolecular coupling agent, low-molecular-weight polybutadiene liquid rubber(LMPB)-maleic anhydride(MAH), was synthesized using solution polymerization and it was used to modify nano-titanium dioxide(nano-TiO2). we further study the solvent effect in the modification processs by changing different polar solvents. The structure, number-average molecular weight, molecular weight distribution and thermal properties of LMPB-g-MAH were systematically investigated by FT-IR、GPC and TGA; The surface properties of modified nano-TiO2 were systematically investigated by FT-IR, nano-particle size analysis, TGA, contact angle analysis, hydrophobic, sedimentation test and TEM. The results showed that the macromolecular coupling agent can covalently bond on the surface of nano-TiO2 particles in the different solvent environment, while nano-sized TiO2 modified in the mixed solvent can achieve the better result than that modified in the pure solvent. The modified mechanism was also further discussed.2. Macromolecular initiator:PAN-Br and several kinds of block copolymers: PAN50-b-PGMA9, PAN5o-b-PGMA22, PAN5o-b-PGMA37, PAN5o-b-PGMA5O were successfully synthesized by atom transfer radical polymerization(ATRP). The structure of the macroinitiator and block copolymers were confirmed by FT-IR,1H-NMR,13C-NMR. Thermal properties of macroinitiator and block copolymer were characterized by TGA. The block copolymers were used for the surface modification of nano-aluminum nitride (AlN) in the mixed solvent of ethyl acetate-DMF. The properities of modified nano-AIN and raw nano-AlN were characterized by sedimentation test, FT-IR, TGA, contant angle analyser, nano-particle, size analyser and TEM. The results showed that nano-AIN modified by PAN50-b-PGMA50 in the mixed solvent of ethyl acetate and DMF at 85℃ possessed the good dispersibility. The active groups on the surface of nano-AIN particles could interact with epoxy group of PAN50-b-PGMA50-The using efficiency of PAN5o-b-PGMA5o was 78%, and chemical using efficiency reached 41.57%. After modified, the hydrophobicity of AIN was increased and contact angle changed from 21° to 62.5°. Nano-AIN particles modified by PAN50-b-PGMA50 could be well dispersed in ethyl acetate.