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Anhydrous lanthanum chloride manufacturers share research progress in preparation and application of cerium dioxide nanomaterials (Part 3)

2022-06-21 13:20:48
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(Continued)


The anti pollution flashover coating with room temperature vulcanized silicone rubber (RTV) as the main component has excellent hydrophobicity, hydrophobic mobility, electrical insulation and other characteristics, and has become the first choice of anti pollution flashover coatings for power transmission and transformation equipment in the power system. However, in recent years, with the rapid development of modern heavy industries such as chemical industry, coal and steel, the environmental pollution caused by them has become increasingly serious, which makes the insulation performance of transmission line insulators decline and pollution flashover accidents occur frequently, causing serious consequences for personal safety and industrial and agricultural development. Therefore, the research and development of high-performance silicone rubber materials for anti pollution flashover has become an urgent need for power security.


In order to further improve the service life of RTV, researchers have done a lot of research work by improving the base material, composition, structure and other methods of RTV, and have also made some progress.


However, the above studies mainly focus on the effects of nano oxides, especially nano CeO2, on the heat resistance and corrosion resistance of silicone rubber, and relatively few studies on the role of silicone rubber in weather aging resistance, especially in ultraviolet aging resistance under exposure environment. Therefore, this paper introduces nano CeO2 into silicone rubber to study the effect of nano CeO2 on the anti ultraviolet aging strength and hydrophobic performance of RTV, so as to improve the outdoor service life of RTV.


Effect of Nano-CeO2 on aging resistance of RTV silicone rubber coating


3.1 experimental raw materials


PRTV, Dezhou Mingao Power Technology Co., Ltd; Ammonium bicarbonate (NH4HCO3), Tianjin Guangfu Fine Chemical Research Institute; Urea (CO (NH2) 2), Tianjin Guangfu Fine Chemical Research Institute; Lanthanum chloride, Nanjing Chemical Reagent Co., Ltd; Cerium chloride, Nanjing Chemical Reagent Co., Ltd; Hydrochloric acid, Beijing chemical plant; Glacial acetic acid, Beijing chemical plant; Sodium hydroxide, Tianda chemical reagent factory, Dongli District, Tianjin; Ethanol, Tianda chemical reagent factory, Dongli District, Tianjin; Ammonia (NH3 · H2O), Tianda chemical reagent factory, Dongli District, Tianjin; Zinc stearate (2nst2), Zhongshan huamingtai Chemical Co., Ltd; CTAB, Sinopharm Chemical Reagent Co., Ltd; Polyethylene glycol (PEG), Shanghai Xilong Biochemical Technology Co., Ltd; Silane coupling agent kh151, Guangzhou Baocheng New Material Technology Co., Ltd., PRTV, znst2 and silane coupling agent kh151 are industrial grade reagents, and others are chemically pure.


3.2 main instruments and equipment


Scanning electron microscope: Hitachi s-3400n Hitachi Instruments Co., Ltd; Ultraviolet visible spectrophotometer: uh4150, Hitachi; Fourier transform infrared spectrometer: Bruker tensor27, Germany; Contact angle measuring instrument: caioob, Shanghai yingnuo Precision Instrument Co., Ltd; UV aging test box: UVB-313 Zn-P, Beijing Zhongke Boda Instrument Technology Co., Ltd.


3.3 preparation of nano CeO2


Using rare earth chloride, ammonia, ammonium bicarbonate and urea as main raw materials, CeO2 precursor was prepared by direct precipitation method with polyethylene glycol or CTAB as dispersant. After filtration and drying, it was placed in a muffle furnace and annealed to obtain nano CeO2 powder. The morphology and crystal structure are shown in Fig. 1. It can be found from Fig. 1 that the particle size of CeO2 powder is a nanorod around 100 nm, and the XRD peak position comparison standard pattern (34-0394) is CeO2, And the peak position is widened due to the nanostructure.


Figure 1 nano CeO2 rod and kh151 modified CeO2 rod

Preparation of 3.4 nano CeO2 rod modified anti pollution flashover coating


Nano CeO2 rods with different mass fractions were dispersed into the anti pollution flashover coating, and fully stirred at room temperature for 15min to obtain the nano CeO2 rod modified silicone rubber coating. Table 1 shows the specific formula composition.


Morphology of 3.5 nano CeO2 rod modified silicone rubber coating


According to the experimental method in 1.4, the nano CeO2 rods were surface modified, and according to the experimental conditions in Table 1, the nano CeO2 rods were uniformly dispersed into the silicone rubber coating to observe the uniformity of RTV Coating on the material surface. The experimental results are shown in Fig. 2.


Figure 2 RTV morphology of nano CeO2 before and after surface modification

It can be seen from figs. 2a and 2b that the introduced nano CeO2 rods are dispersed in the coating. It can be seen from Fig. 2C that when the No. 1 unmodified nano CeO2 rods enter the organic phase, serious agglomeration or phase separation occurs, which not only results in poor dispersion effect of cerium oxide, but also affects the smoothness and beauty of the coating. The No. 2 and No. 3 surface modified nano CeO2 rods do not appear the same serious agglomeration and phase separation phenomenon as No. 1, and are well dispersed, And the dispersion did not decrease with the increase of the addition amount.


Study on properties of 3.6 nano CeO2 rod modified anti pollution flashover coating


3.6.1 ultraviolet visible spectrum analysis


Ultraviolet visible spectroscopy can characterize the characteristics of silicone rubber coating in light absorption, and the degree of diffuse reflection, that is, light absorption, directly affects the degree of aging resistance of silicone rubber coating in outdoor. The ultraviolet visible spectrum can be used to analyze the ultraviolet shielding effect of different additive components on the silicone rubber coating.


In order to further test the anti-aging effect of the nano CeO2 rod on the silicone rubber coating substrate, the influence was analyzed by using the spectral data of light absorption in the long wavelength range from 1200 nm near-infrared light to 300 nm ultraviolet light. The modified nano CeO2 rod sample (1.5% (mass fraction, the same below)) was doped into RTV to make the coating and then compared after 560h climate aging resistance. At the same time, the RTV without nano CeO2 was also compared after 560h climate aging resistance. Fig. 3 is the scanning spectrum of ultraviolet visible spectrum test before and after aging.


Fig. 3 ultraviolet visible spectrum of RTV under different conditions

It can be seen from Fig. 3 that after 560 hours of weather aging resistance test, the reflection spectrum of the silicone rubber coating sample without adding nano CeO2 changed significantly in the near-infrared region, while the spectral characteristics of the silicone rubber coating sample with adding 1.5% nano CeO2 remained basically unchanged in the range of 1200 nm to 300 nm without obvious change. It is proved that nano CeO2 has an obvious effect on the weather aging resistance of silicone rubber coating samples, and maintains the working stability of the coating. The obvious change of the blank sample in the near-infrared region should be attributed to the group change inside the coating sample, and the specific chemical key position change should be determined and judged by the infrared spectrum test.



3.7 conclusion

(1) After the nano CeO2 rods are treated with silane coupling agent kh151, a large number of carbon containing groups are added on the surface, so that no more than 1.5% of the nano CeO2 rods can be evenly dispersed in the silicone rubber coating.

(2) After 560 hours of aging resistance test, the influence of nano CeO2 rod on the aging resistance of RTV was characterized and analyzed by means of ultraviolet visible spectrum analysis, infrared spectrum analysis and contact angle test. The results show that the introduction of 1.5% nano CeO2 rod can effectively maintain the physical and chemical characteristics of the silicone rubber coating, such as ultraviolet visible spectrum, infrared spectrum and hydrophobicity, and can play an obvious role of ultraviolet shielding.



Main references

(1) Zhang Peng, et al., research progress on the preparation of nano cerium dioxide and its photocatalytic performance, modern chemical industry, network launch date: 2020-08-26

(2) He Chuan, et al., oxidation characteristics of elemental mercury of CeO2 modified regenerated SCR catalyst, modern chemical industry, online launch date: 2020-07-16

(3) Li Lin, et al., effect of nano CeO2 on the aging resistance of RTV silicone rubber coatings, rare earth: 2020 (1)



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