Effect of Organic Montmorillonite on the Micromorphology and Water-Tree Aging Properties of XLPE/OMMT Nanocomposite Dielectrics
Crosslinked polyethylene/organic montmorillonite(XLPE/OMMT)nanocomposite dielectrics were prepared by melt blending method to investigate the effects of organic montmorillonite types on the micromorphology and water-trees aging properties of the nanocomposite dielectrics.The specimens were tested by mechanical properties.It is found that the comprehensive mechanical properties reach the best when the mass fraction of OMMT is 0.5%.The micromorphology of the specimens was investigated by differential scanning calorimetry and scanning electron microscope.The organic montmorillonite(OMMT3)organically modified with dioctadecyl benzyl quaternary ammonium salt and refined,plays an obvious role of heterogeneous nucleation,leading to a more perfect crystal with a crystallinity up to 25.3%,and the average size of the crystals is only 16.67 μm.Accelerated water-tree aging tests were performed on each specimen by water needle electrode method.The stripping of the dispersed OMMT3 layer forms a more tortuous labyrinth path,and its barrier effect on water molecules and the restraint of XLPE crosslinked network structure on the movement of molecular chains,the combined effect of the two effectively inhibits the growth of water trees in XLPE/OMMT3 specimen,and the initiation probability is reduced to 23.4%.The chemical structure of the water trees before and after aging was characterized by Fourier transform infrared spectroscopy.The test results indicate that the increase of carbonyl index and vibration peak of hydroxyl in the water-tree region of nanocomposite dielectrics indicate that water-tree aging is due to electrochemical degradation,while the chain breakage of XLPE/OMMT3 is less in the process of water-trees growth,showing excellent thermal and oxygen aging resistance.
organic montmorillonitecrosslinked polyethylenenanocomposite dielectricmicromorphologywater tree