| The concept of polymer nanocomposites was advanced in the early 80s, and soon it become to be the focus of the research. The in-situ polymerization method can be used to achieve the industrialization of polymer nanocomposites. Firstly, nano-particles or modified nano-particles were dispersed into polymer raw materials, and then polymer nanocomposites were prepared via in-situ polymerization. The nanocomposites obtained via in-situ polymerization perform well because of the homogeneous dispersion and good compatibility of nano-particles. Besides, the in-situ polymerization method is effective and simple.In this paper, crude nano-particles and nano-particles modified by macromolecular surface modifier which we designed and synthesized were dispersed by high pressure shearing homogenizer (HPSH) into polymer diols, and then polyurethane nanocomposites were compounded via in-situ polymerization. The research indicated that nano-particles dispersed well in the polyurethane matrix, and played an important role in the increase of the performance as well as the reduction of the cost of polyurethane. There are three chapters constitute the thesis:The first chapter is the introduction which presents the frequently used inorganic nanoparticles, as well as their surface modification methods, and their application in polyurethane modification. Finally, the design of the whole paper is advanced.In the second chapter, nano-silica/polyurethane composites were synthesized via in-situ polymerization. Firstly, poly (tetramethylene ether glycol) (PTMEG) and poly (butylenes adipate glycol) (TPEG) and ethylene glycol (EG) and N, N-Dimethylformamide (DMF) and nano-silica were mixed as a certain proportion. Then the mixture treated by high-speed shearing machine and high pressure shearing homogenizer for 10 minutes respectively was placed in a three-neck flask with 4> 4'-diphenylmethane diisocyanate (MDI), The polymerization of polyurethane was carried out at 90℃under nitrogen atmosphere for 3 h. During the reaction, a small amount of MDI was appended according to the viscosity of the system. The composite resins were studied by FTIR, GPC, TGA and SEM. The result showed that the nano-silica in composites method possess homogenous dispersion, and the addition of nano-silica enhanced the mechanical properties of the composites but not reduce the molecular weights.The third chapter is the synthesis and application of macromolecule surface modifier (BA)m-(MMA)n-COOH. Firstly, the solution consisted of Methyl methacrylate (MMA, monomers), Butyl Acrylate (BA, monomers), Mercaptoacetic acid (2-MA, chain transfer agent) and 2,2'-Azobis (2-methylpropionitrile) (AIBN, radical initiator) in the ratio of 500/500/25/1 was add into toluene within 2.5h at 110℃, then the reaction was carried out for four hours. After that, change the device for the distillation and heated to 170℃to remove the solvent and unreacted monomers. The obtained compound was hydroxyl-terminated polyacrylate copolymers. The structure and thermal stability of copolymers were analyzed by FTIR, 1H NMR,13C NMR, GPC, TGA and DSC. The result indicated that the number-average molecular weight (Mn) of the macromolecule surface modifier which were hydroxyl-terminated was about 3500. The main weight loss of the copolymer which had a Tg was between 300℃and 400℃. Then the macromolecule surface modifier (BA)m-(MMA)n-COOH was used in the surface modification of nano-CaCO3. FTIR and TGA demonstrated that macromolecular modifier bonded covalently with the hydroxide radical on the surface of nano-CaCO3. Size distribution analyzer, sedimentation experiment and TEM were exerted to show that the modified nanoparticles dispersed well in organic solvent without serious agglomeration. Contact angle test investigated that the hydrophile of modified nanoparticles was decreased. Finally, the modified nanopartilces were dispersed into raw materials of polyurethane and nano-CaCO3/polyurethane composites were synthesized via in-situ polymerization. SEM showed that nano-CaCO3 in the nanocomposites was homogenously dispersed in the polyurethane matrix. TGA and tensile strength test indicated that the addition of nano-CaCO3 had no effect on the thermal stability of resins but a small amount of nano-CaCO3 would enhance the tensile strength. |
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