savin1_20200909_113144毕设manuscript-iseim2014_jielinguo no 105

1、Conference Proceedings of ISEIM 2014Study on Electrical Properties of Micro-nano Structured Epoxy CompositesJielin Guo1, Yu Chen1*, Zirui Jia1, Toshikatsu Tanaka2, Jielong Wu3, Yonghong Cheng 11, State Key Laboratory of Electrical Insulation and Power Equipment Xian Jiaotong University, Xian, Shaanx

2、i, P.R.China, 7100492, IPS Research CenterWaseda University, Kitakyushu, Fukuoka, Japan, 808-0135 3, Shaanxi Electric Power CompanyXian, Shaanxi, P.R.China, 710048*E-mail: Abstract: With the aim of reducing the insulation faults in GIS and achieving the purpose of GIS device mi

3、niaturization, it is very important to develop a new type insulation material. In this paper, the micro-nano Al2O3/Epoxy composites were proposed, and its dielectric breakdown strength wasbreakdown strength and this has been verified 2. Over the past few years, there has been increased interest in t

4、he use of nano-sized fillers as additives to polymer nanocomposites materials. Electrical insulation using nanocomposites may provide superior performance when compared with conventional microfilled materials, such as lower dielectric losses and increased dielectric strength. Such improvements can c

5、reate apparatus that are more compact and last longer than what is available presently. For the thermal properties of modified epoxy-based polymer composites, some researchers have found that the addition of the nanofillers has higher glass transition temperature than pure epoxy resin 3. Others foun

6、d that after adding the nanoparticles, epoxy glass transition temperature may decrease and this phenomenon relates with mass fraction of fillers and the combination between the fillers and epoxy resin 4. Others found that thermal stability of composite increases with the content of micro-filler 5.Ou

7、r research focus on the insulation and thermal properties of micrometer and nanometer sized composites based on epoxy resin. In this paper, six kinds of composites specimen have been prepared and were observed through Scanning Electron Microscope (SEM). The experiment results of decomposition temper

8、ature, glass transition temperature, dielectric constant, conductivity, dielectric loss and the breakdown voltage are presented.investigated. Nano-fillers and micro-fillers(-Al2O3with apurity of 99.9%, particle size range at 1221 m for microfillers, and average particle size with 30 nm for nano fill

9、ers) were dispersed in the epoxy resin with shear force and ultrasonic vibration. The specimens were produced by a curing reaction with the hardener. Six kinds of material were prepared for this investigation, which were neat epoxy, nano-composite (loaded with 5 wt% nano-Al2O3 fillers), nano-composi

10、te (loaded with 5 wt% nano-TiO2 fillers),micro-composite (loaded with 65wt%micro-Al2O3fillers),nano-micro-mixture-composites(loaded with 2 wt% nano-Al2O3 fillers and 63 wt% micro-Al2O3 fillers), nano-micro-mixture-composites (loaded with 2 wt% nano-TiO2 fillers and 63 wt% micro-Al2O3 fillers).Disper

11、sion of the micro and nano Al2O3 in the epoxy resin was observed through SEM, and thermal behavior was analyzed with Thermo-Gravimetric Analysis (TGA) and differential scanning calorimeter (DSC). The dielectric constant and dielectric loss were measured by broadband dielectric spectrum test facility

12、. Dielectric breakdown experiments werecarriedoutthroughthesphere-plate configuration under AC voltage.sample-sphereKeywords: Epoxy Composite, Power Frequency Voltage, Thermal Stability, Insulation PropertyBreakdownII.EXPERIMENTALI.INTRODUCTIONSample PreperationIn this paper, six kinds of specimen w

13、ere prepared for investigation, which were neat epoxy (BER), 5 wt% nano alumina (Al2O3)/epoxy composite (NC1), 5 wt% nano titanium dioxide (TiO2)/epoxy composite (NC2), 65 wt% micro alumina/ epoxy composite (MC), 2 wt% nano alumina (Al2O3)and 63wt% micro alumina(Al2O3)/ epoxy composite (NMMC1) and 2

14、 wt% titanium dioxide (TiO2) and 63wt% micro alumina(Al2O3)/ epoxy composite (NMMC2). The materials used to prepare samples are shown in Table 1 and the filler amounts of epoxy-based composites are shown in Table 2. The Diglycidylether of bisphenol-A type epoxy resin (EPON-828) was cured by ethyltet

15、rahydrophthalic anhydride curing agent and N,N-dimethylbenzylamine accelerator to form a cross-linked structure. In order to disperse the micro fillers in epoxy homogeneously, the solution was mixed via the mixer of ARE-310 (THINKY Co.)Enclosed gas insulated switchgear (GIS) has been widely used and

16、 plays an important role in the power system. Epoxy resin is an indispensable material for insulation system. In order to obtain high thermal stability and improve insulation properties, epoxy resins should be mixed with appropriate micrometer sized fillers or nanometer sized fillers. The use of ino

17、rganic fillers such as silica, alumina, etc. in polymeric materials has been done for many years. Addition of these fillers in the formulation reduces cost, improves fire resistance and tree initiation phenomena 1. For outdoor applications, they enhance resistance to dry band arcing and surface disc

18、harges.However, such micro-filled epoxy resins will suffer lower breakdown strength. Composites with addition of nano-micro fillers can be useful to raise the once loweredACKNOWLEDGMENTThis work is supported by China Postdoctoral ScienceFoundation (2013M532047)，Shaanxi Provincial Science andTechnolo

19、gy Project - Industrial Research Programs (2013K09-41) and State Key Laboratory of Youth Innovation Fund (EIPE13310).Conference Proceedings of ISEIM 2014TABLE IMATERIALS USED TO PREPARE COMPOSITES(e)NC1(f)NC2Figure 1.SEM images of samples.Thermal properties of compositesThermal behavior of the compo

20、sites was analyzed with TGA/DSC equipment（ METTLER TOLEDO Co.）. The heating process was set from 25 to 150 ， kept the temperature at 150 for 10 minutes and then the temperature was kept rising to 600 and lasted for 10 minutes. The heating rate was 10 /min and the protection gas was nitrogen with a f

21、low of 20 ml/min.TABLE II. FILLER AMOUNTS OF EPOXY-BASED COMPOSITESBreakdown strengths test in a sphereplate sample-sphere electrode systemDielectric breakdown experiments were carried out in such an electrode system that a dielectric plate sample of 0.3 mm in thickness was inserted between a pair o

22、f sphere steel balls of 25 mm in diameter as shown in Figure 2, and a whole electrode system was immersed in transformer oil to avoid surface flashover. High voltage of 50 Hz was applied via a transformer. After each measurement, there will be 1 minute interval before the next measurement The voltag

23、e applied was increased at a rate of 1 kV/s until breakdown. The oil was stirred after every breakdown measurement and replaced after10 measurements to ensure that the experiment data were not affected due to the by-products of degradation.Broadband dielectric spectrum test in room temperatureDielec

24、tric spectroscopy is a technique for real and imaginary permittivity measurements which over a frequency range (e.g. 1 Hz 1 MHz) 6. Broadband dielectric spectrum test system can be used to accurately measure the dielectric properties of the material parameters such as dielectric constant, dielectric

25、 loss tangent and electrical conductivity and so on. A voltage of 1 V was applied to the samples and their permittivity values were measured over a frequency range of 10-1 Hz to 106Hz.III RESULTSFor the nano-sized fillers, they were mixed by the ultrasonic cell crusher. Finally, the hardener was mix

26、ed with the solution. Then, the intermixture was degassed in a vacuum drying oven at 50 C for 1 h. Thus obtained solution without any air bubbles was decanted into an annular cast mold which has a diameter of 60 mm and thickness of 0.3 mm space. A resulted plate sample was then cured in an oven at 1

27、00 C for 2 h, post -cured at 150 C for 12 h, and finally cooled down gradually to room temperature to obtain a final shape of the sample. In order to improve the interface between micro-fillers and epoxy, silane coupling agent was added.Microstructures of the composite were imaged by SEM at an accel

28、eration voltage of 20 kV (VE9800S Keyence Co.). Fig. 1 SEM images of nano-Al2O3/epoxy composite, nano- TiO2/epoxy composite, nano-micro-Al2O3/epoxy and nano- micro-TiO2/epoxy composite shown indicate that good filler dispersion was obtained.(a)BER(b) MCHigh voltage inputElectrodeSpring 25mm (c) NMMC

29、1(d) NMMC2SampleGroundFigure 2. The structure of sphere-plate sample-sphere electrode systemCopper Ball- Copper electrodeTransformeroilholderSpecimenNano-fillerMicro-fillerTypeAmountswt%TypeAmountswt%BER-NC1Al2O35-NC2TiO25-MC-Al2O365NMMC1Al2O32Al2O363NMMC2TiO22Al2O363Epoxy ResinDiglycidyl ether of b

30、isphenol-A type epoxy resin (EPON-828)HardenerMethyltetrahydrophthalicanhydride (MeTHPA)AcceleratorN,N-dimethylbenzylamine BDMASilane Cupling AgentK550Micro Al2O3-Al2O3 with purity of 99.9% and average particle size ranged from 12 to 21mNano Al2O3-Al2O3 average particle size is 30nmNano TiO2Anatase

31、TiO2 average particle size is 10nmConference Proceedings of ISEIM 2014Weibull Distribution is commonly used for breakdown strengths in nanodielectrics7. The Weibull distribution plot of the micro and the micro-nanofilled samples are shown in Figure 6. Micro composites show lower breakdown strength t

32、han their neat epoxy 8, but they are expected to exhibit some increase.Breakdown strength decreased down by 17.26 % from 69.11kV/mm to 57.18 kV/mm when epoxy resin was loaded by micro Al2O3 fillers. It actually increased by 8.1 % from57.18 to 62.21 kV/mm when the micro Al2O3/epoxy composite was load

33、ed by nano Al2O3 fillers. However, when the micro Al2O3/epoxy composite was loaded by nano TiO2 fillers, breakdown strength decreased down by 4.02% fromTABLE III TEMPERATURE WITH SAME RESIDUAL WEIGHT RATEFig. 3 shows TGA test result for the samples under the same heating rate. First, according to th

34、e TGA curve, we can figure out that the micro-nano structured epoxy composites have better thermal stability than the neat epoxy. In order to prove this, we chose the same residual weight ratio to compare the thermal decomposition temperature.Table III shows the thermal decomposition temperature und

35、er the same residual weight ratio. From Table III we can infer that after using inorganic fillers to modify epoxy, thermal decomposition temperature can be improved under the same residual weight ratio.DSC can be used to study physical changes in the process of polymer material. Fig. 4 shows the TGA

36、 and DSC curves of the nano-Al2O3/epoxy composite. In Figure 4, the blue line represents the TGA curve and the red line represents the DSC curve. From the exothermic peak in DSC curve, the glass transition temperature can be speculated. When the composite begin to decompose, there is an endothermic

37、peak in the DSC curve. The rest of the samples all have the same feature. The glass transition temperature (Tg) of the micro-57.18kV/mmto54.88kV/mm.Breakdownstrengthdecreased down by 25.25% from 69.11 kV/mm to51.66kV/mm when epoxy resin was loaded by nano Al2O3 fillers and 12.32% from 69.11kV/mm to

38、56.79 kV/mm when epoxy resin was loaded by nano TiO2 fillers.Figure 5. The breakdown strengths of the six kinds of samplesnano/epoxy composite has changed fromthe beneat epoxy. statisticallyThese differences significant.werenotfoundtoWeibullProbability Plot0.960.900.751.00.80.50BERMCNMMC1

39、NMMC20.2NC1NC20.100.00100200300Temperature (C)4005006000.05Figure 3 Thermo gravimetric curves of epoxy composites4550556065707580Breakdown Strength(kV/mm)Figure 6. Weibull distribution plot for the six kinds of samples1251.01007.57.06.56.05.55.04.54.03.50.8750.6500.4250.200.00100200300400500600Tempe

40、rature (C)3.010-1100101102103104105106Figure 4.Thermal properties of nano-Al2O3/epoxy composite.Frequency(Hz)Figure 7. Real permittivity plots for samples at room temperature.Residual RateResidual RateHeat Rate(mW)Real PermittivityProbabilityBERMCNMMC1NMMC2NC1NC2BER MC NMMC1 NMMC2 NC1 NC2Residual ra

41、te T()Items95%80%60%40%20%BER335.5375.5395.5409.5428.5NC1334.5371389403493NC2338381398412453.5MC361395-NMMC1369404-NMMC2358.5396-Conference Proceedings of ISEIM 20140.05of the samples. The permittivity of the composite material depends on each volume fraction and each permittivity 12.0.04IV.CONCLUSI

42、ON(I).The addition of micro and nano Al2O3 fillers into epoxy can increase the thermal stability. But the change of the glass transformation temperature is not significant.(II).The introduction of inorganic fillers can improve permittivity value and can also increase the dielectric loss. The real pe

43、rmittivity value: NMMC1 MC NMMC2 NC2 NC1 BER at 50Hz. Also, the micro-nano/epoxy composite has higher conductivity.(III). Adding micro and nano Al2O3 fillers into epoxy will cause some reduction in dielectric breakdown strength. Its worthwhile to consider continuing to add nano fillers into micro-co

44、mposite to help compensate such reduction to a certain degree. Micro-nano/epoxy composites are considered to show lower breakdown voltage than neat epoxy. The breakdown strength also relate with the permittivity of the inorganic filler. The higher the inorganic nano fillers permittivity is, the high

45、er breakdown strength the micro- nano/epoxy composite has. The result of the breakdown strength: BER NMMC1 MC NC2 NMMC2 NC1.(IV).Large interaction zone can have a major impact on the permittivity values of nano-composite materials as compared to micro-composite materials. This may explain the fact t

46、hat nano-filled samples have lower values of permittivity and tan over micro-filled samples.0.030.020.010.0010-1100101102103104105106Frequency (Hz)Figure 8.Tan plots of studied epoxy samples at room temperature.543210104105Frequency (Hz)106Figure 9 Real Conductivity plots for samples at room tempera

47、ture.Fig. 7 and 8 show the real permittivity and the tan plots of the different samples. Fig. 9 shows the conductivity plots for samples at room temperature. The introduction of inorganic fillers has a higher permittivity value than the base polymer 9. The real permittivity and the tan plots show th

48、at there is a significant difference in the measured values of the unfilled when compared with the micro and micro- nanofilled samples.REFERENCESYu Chen, T. Imai, Y. Ohki, T. Tanaka. “Tree initiation phenomena in nanostructured epoxy composites”J. Dielectrics and Electrical Insulation, IEEE Transact

49、ions on, 2010, 17(5): 1509-1515.K. Okamoto, Y. Ohki, T. Tanaka. “The role of nano and micro particles on partial discharge and breakdown strength in epoxy composites”J. Dielectrics and Electrical Insulation, IEEE Transactions on, 2011, 18(3): 675-681.X. Kornmann, Berglund, L.A., Lindberg, H, “Stiffn

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51、hida and S. Rimdusit, “Very High Thermal Conductivity Obtained by Boron Nitride-filled Polybenzoxazine Thermochim”, ACTA, Vol. 320, pp. 177-186, 1998.A. K. Jonscher, Dielectric Relaxation of solids, Chelsea Press, 1983.S. Singha and M. J. Thomas, “Dielectric Properties of Epoxy Nanocomposites”, IEEE

52、 Trans. Dielectr. Electr. Insul., Vol. 15, pp.12- 23, 2008.A. K. Jonscher, Dielectric Relaxation of solids, Chelsea Press, 1983.S. Singha and M. J. Thomas, “Dielectric properties of epoxy nanocomposites”, IEEE Trans. Dielectr. Electr. Insul, Vol. 15, pp12- 23, 2008.Z. Li, K. Okamoto, Y. Ohki, T. Tan

53、aka. “Effects of nano-filler addition on partial discharge resistance and dielectric breakdown1III.DISCUSSIONThe addition of micro and nano Al2O3 fillers into epoxy can increase the thermal conductivity. But they will cause some reduction in dielectric breakdown strength 10. This becomes a big issue to solve in power electronics field. It would be worthwhile to add nano fillers into micro- composite to help compensate such reduction to a certain degree. Furthermore, the breakdown voltage of the micro- nano structured epoxy composite re