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Preparation, Surface-modification of Nano-ZnO Whiskers and Its Application in Polyacrylate Coating

Author: HeWeiWei
Tutor: LiYuPing
School: Hunan University
Course: Materials Science
Keywords: Nano-ZnO whiskers Preparation Characterization Modification Dispersion Composite coatings Strengthening
CLC: TB383.1
Type: Master's thesis
Year: 2006
Downloads: 84
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Abstract


The suitbale technological parameters of synthesizing nano-ZnO whiskers by a one-step wet chemical method with low-temperature in normal pressure were investigated in this paper, and the modification effects of as-prepared nano-ZnO whiskers by built surfactant in different dispersion condition were also studied. The polyacrylate nanocomposite coatings were parepared by the dispersion of nano-ZnO whskers in polyacrylate, the hardness and other basis performance of nanocomposite film were evaluated.Through changing the different synthetic parameters in turn to prepare final products, and characterizing as-prepared products with DSC-TG, XRD, TEM,FT-IR, the best technological parameters of synthesizing nano-ZnO whiskers were attained. 1.2 mg·L-1 ZnSO4 was added drop-wise into 3.0 mg·L-1 NaOH under stirring in baker that was heated at a temperature of 55°C in thermostat water bath, following that, 0.01 mg·L-1 C18H29NaO3S （DBS） was introduced into the aforementioned solution. In the monitoring of pH meter, the pH value of reaction mixture was adjusted to above 9 though controlling the amount of ZnSO4 added. 2 hours later, the precursor was harvested by filtering under vacuum and washing 3 to 5 times with distilled water and absolute ethanol, finally, the naonsized ZnO whiskers was attain after the precursor was dried in a vacuum oven 4h at 80°C. Depending on the synthetic conditions used, ZnO can be formed directly in aqueous solution without calcination. Transmission electron microscope （TEM） observation reveales that nano-ZnO whiskers are needle-like or rod-like morphology, they have diameters ranging from 30 to 50 nm and lengths up to 400nm. The nano-ZnO whiskers show high crystalline pattern, and all the diffraction peaks can be well assigned to the hexagonal-phase ZnO reported in the literature （Wurtzite-type, space group P63mc）, the calculated cell parameters of a0 and c0 are 3.25 and 5.21·, respectively. None other phases can be observed in the patter, verifying that the sample is phase-pure. The HRTEM image shows the lattice spacing of 0.26nm, corresponding to a lattice constant of the （002） plane of wurtzite structured ZnO, and implies the preferred growth orientation of ZnO nanorods along the （002） plane.In modification of nano-ZnO whiskers experiments, using DBS / PEG400 which containing 30% DBS as built modifying agent, controlling the concentration of DBS / PEG400 is 400mg·L-1, and agitating for 60min, the best effects of modification can be gotten. The absorbance of modified nano-ZnO whiskers dispersion is higher than that of unmodified, dispersion and stability in system is also better.The polyacrylate nanocomposite coatings were parepared through dispersing the nano-ZnO whiskers into polyacrylate, After detected some basic performance of the composite coating, we attained the conclusion that, the composite coatings with 6% nano-ZnO whiskers contained have the best comprehensive performance, not only film hardness is strengthened, stain-resisting and scrub resistance of the coating are much increased, but also the coating’s thixotropy and storage stability are clear improved.

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