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A series of star-shaped polylactic acid was synthesized using L-lactic acid (L-LA) and octa(γ-chloroammoniumpropyl) octasilsesquioxane (POSS-NH3Cl) by in the presence of stannous(II) octanoate (Sn(Otc)2) catalyst. The structures and properties of these dendritic polymers were characterized by FTIR, 1H-NMR and TGA, respectively. These results demonstrated that the chemical reaction between POSS-NH3Cl and L-LA had been taken place, and the novel star-shaped polylactic acid (POSS-g-PLLA) had been synthesized. And thermal properties, such as melting temperature and decomposition temperature, were obviously improved along with the increment of the added amount of POSS-NH3Cl. The decomposition temperature of POSS-g-PLLA was higher ca. 70℃ higher than that of PLLA, also higher 65℃ than that of POSS-NH3Cl/PLLA.

In the sodium silicate electrolyte system, the uniform ceramic films formed on AZ91D magnesium alloys were obtained by the pulse power when the current density is 40mA/cm2. The morphology, phase composition, anticorrosion and abrasion resistance behaviors in corrosive medium were studied scanning electron microscopy (SEM). The results show that Micro-arc oxidation film is of double-layer structure (loose layer and compact layer), uniform surface and local cracks. Micro-arc oxidation treatment enhanced the anticorrosion of magnesium alloy. The corrosion potential of micro-arc oxidation film is more increased by 94mV than that of the magnesium alloy substrate. The abrasion of the film will be reduced in corroding medium.