148 / 2018-08-25 14:36:24

Effect of particle size of inorganic particles on dielectric strength of composites

Composite; crystalline; breakdown; particle size ; zinc oxide

In order to study the effect of inorganic filler particle size on the dielectric strength of polymer, the low density polyethylene (LDPE) was used as the matrix, and the zinc oxides with particle sizes of 9 nm, 30 nm, 100 nm, 200 nm and 1 μm respectively, were used as fillers. Pure LDPE and five kinds of composites each having a content of 2wt% were prepared by melting blending (LDPE, 9n, 30n, 100n, 200n, 1m). Scanning electron microscopy (SEM) was used to investigate the dispersibility of zinc oxide particles in the polymer matrix. The crystallinity of specimens was measured by differential scanning calorimetry (DSC). The AC and DC breakdown characteristics of the pure LDPE and composites were studied. The experimental results show that the particle dispersibility is significantly improved with the increase of the particle size of zinc oxide. The crystallinity of the composite increases first and then decreases with the increase of ZnO particle size. When the particle size of zinc oxide is 30 nm, the crystallinity of the composite is highest, which is 48.33%. The AC and DC breakdown strength of composites increases first and then decreases with the increase of ZnO particle size (30n>9n>100n>LDPE> 200n>1m). The AC and DC breakdown strength of pure LDPE is 127.5 kV/mm and 299.0 kV/mm, respectively. When the particle size of zinc oxide is 30 nm, the AC and DC breakdown strength of the composite is highest, which is 138.0 kV/mm and 340.4 kV/mm, respectively.In order to study the effect of the particle size of the inorganic filler on the dielectric strength of the polymer, low density polyethylene (LDPE) was selected as the matrix material, and zinc oxide (ZnO) with particle diameters of 9 nm, 30 nm, 100 nm, 200 nm and 1 μm, respectively, were used as the inorganic fillers. Five kinds of composite materials with content of 2wt% and pure LDPE were prepared by melt blending. Scanning electron microscopy (SEM) was used to investigate the dispersibility of ZnO particles in the polymer matrix. The crystallinity of different samples was measured by differential scanning calorimetry (DSC). The AC and DC breakdown characteristics of the five composite materials and pure LDPE were tested.
The experimental results show that the smaller the ZnO particles, the easier it is to agglomerate in the matrix and it is difficult to disperse uniformly. The crystallinity of the composites is higher than that of pure LDPE. The crystallinity of the composites increases first and then decreases with the increase of ZnO particle size. The highest crystallinity is 40.28% when the ZnO particle size is 30 nm. The results of AC breakdown test show that the AC breakdown strength of pure LDPE is 127.5 kV/mm. The AC breakdown strength of composites increases first and then decreases with the increase of ZnO particle size. When the ZnO particle size is 30 nm, the breakdown strength of composite is the highest, which is 138.0 kV/mm. When the ZnO particle size is 1 μm, the breakdown strength of composite is the smallest, which is 113.4 kV/mm. The results of DC breakdown test show that the breakdown strength of pure LDPE is 299.0 kV/mm, and the DC breakdown strength of composites increases first and then decreases with the increase of ZnO particle size. When the ZnO particle size is 30 nm, the breakdown strength of composite is the highest, which is 340.4 kV/mm. When the ZnO particle size is 1 μm, the breakdown strength of composite is the smallest, which is 257.8 kV/mm.