环氧树脂的湿热老化特性研究
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摘要
为了研究环氧树脂的湿热老化特性,对老化前后环氧树脂试样的质量变化率、红外光谱、扫描电镜图、介电特性及空间电荷特性进行对比分析。结果表明:随着湿热老化时间的增加,环氧树脂材料的质量呈现增大-减小-增大-减小的趋势,裂纹数量不断增加,材料内部发生了氧化反应。在湿热环境下,环氧树脂材料裂解产生的游离小分子与吸收的水分子含量处于动态变化中,使得其介电常数实部(ε′)随着老化时间的增加呈现增大-减小-增大的趋势,而介电常数虚部(ε″)则呈现增大-减小-增大-减小-增大的趋势。利用Debye方程对ε″进行拟合,发现水分分布均匀度对材料的电导损耗具有很大影响,游离小分子含量、吸湿量与极化损耗呈正相关。湿热老化环氧树脂试样干燥后,其ε′和ε″相比老化前均有所减小。但由于其内部结构遭到破坏,不能完全恢复原有电气性能。随着老化时间的增加,环氧树脂材料内部残余空间电荷总量的衰减速率减缓,残留电荷总量增加。
In order to study the hygrothermal ageing characteristics of epoxy resin, the mass change rates, infrared spectra, scanning electron microscope images, dielectric properties, and space charge characteristics of the epoxy resin samples before and after ageing were compared. The results show that with the increase of the hygrothermal ageing time, the mass of epoxy resin shows a trend of increasedecrease-increase-decrease, the crack amount increases continuously, and the oxidation reaction occurs inside the materials. In the hygrothermal environment, the real part of dielectric constant(ε′) of epoxy resin shows a trend of increase-decrease-increase and the imaginary part of dielectric constant(ε″) shows a trend of increase-decrease-increase-decrease-increase with the increase of ageing time, this is because the free small molecules produced by the pyrolysis of epoxy resin and the absorbed water molecules change dynamically. The ε″ is fitted by Debye equation and we find that the water distribution uniformity has great influence on the conduction loss of the materials, and the free small molecules content and the moisture absorption content are positively correlated with polarization loss. After the hygrothermal aged sample is dried, its ε′ and ε″ decrease compared with the unaged sample, but due to the destruction of its internal structure, the original electrical properties can not be restored completely. With the increase of the ageing time, the decay rate of the total residual charge amount in epoxy resin materials slows down, and the amount of residual charge increases.
In order to study the hygrothermal ageing characteristics of epoxy resin, the mass change rates, infrared spectra, scanning electron microscope images, dielectric properties, and space charge characteristics of the epoxy resin samples before and after ageing were compared. The results show that with the increase of the hygrothermal ageing time, the mass of epoxy resin shows a trend of increasedecrease-increase-decrease, the crack amount increases continuously, and the oxidation reaction occurs inside the materials. In the hygrothermal environment, the real part of dielectric constant(ε′) of epoxy resin shows a trend of increase-decrease-increase and the imaginary part of dielectric constant(ε″) shows a trend of increase-decrease-increase-decrease-increase with the increase of ageing time, this is because the free small molecules produced by the pyrolysis of epoxy resin and the absorbed water molecules change dynamically. The ε″ is fitted by Debye equation and we find that the water distribution uniformity has great influence on the conduction loss of the materials, and the free small molecules content and the moisture absorption content are positively correlated with polarization loss. After the hygrothermal aged sample is dried, its ε′ and ε″ decrease compared with the unaged sample, but due to the destruction of its internal structure, the original electrical properties can not be restored completely. With the increase of the ageing time, the decay rate of the total residual charge amount in epoxy resin materials slows down, and the amount of residual charge increases.
引文
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[24]RHAIEM A B,HLEL F,GUIDARA K,et al.Dielectric relaxation and ionic conductivity studies of[N(CH3)4]2Cu0.5Zn0.5Cl4[J].Journal of Alloys and Compounds,2008,463(1):440-445.
[25]LIU Y,AN Z,CANG J,et al.Significant suppression of surface charge accumulation on epoxy resin by direct fluorination[J].IEEE Transactions on Dielectrics and Electrical Insulation,2012,19(4):1143-1150.
[26]ALESSI S,CONDURUTA D,PITARRESI G,et al.Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends.Thermal,mechanical and morphological behaviour[J].Polymer Degradation and Stability,2011,96(4):642-648.
[27]龚瑾,李喆,刘新月.氧化铝/环氧树脂复合材料空间电荷特性与高温高湿环境下交流电场老化[J].电工技术学报,2016,31(18):191-198.
[2]蒋志勇.典型结构的环氧浇注干式变压器漏磁场仿真与分析[J].变压器,2017,54(1):32-37.
[3]黄炎光,易鹭.热老化对干式变压器环氧树脂介电性能的影响[J].绝缘材料,2016,49(9):53-56.
[4]吕小军,张琦,马兆庆,等.湿热老化对碳纤维/环氧树脂基复合材料力学性能影响研究[J].材料工程,2005(11):50-53.
[5]BAO L R,YEE A F.Effect of temperature on moisture absorption in a bismaleimide resin and its carbon fiber composites[J].Polymer,2002,43(14):3987-3997.
[6]ADAMSON M J.Thermal expansion and swelling of cured epoxy resin used in graphite/epoxy composite materials[J].Journal of Materials Science,1980,15(7):1736-1745.
[7]ZHENG Q,MORGAN R J.Synergistic thermal-moisture damage mechanisms of epoxies and their carbon fiber composites[J].Journal of Composite Materials,1993,27(15):1465-1478.
[8]SOLES C L,YEE A F.A discussion of the molecular mechanisms of moisture transport in epoxy resins[J].Journal of Polymer Science Part B:Polymer Physics,2015,38(5):792-802.
[9]王晓洁,梁国正,张炜,等.湿热老化对高性能复合材料性能的影响[J].固体火箭技术,2006,29(4):301-304.
[10]ZOU C,FOTHERGILL J C,ROWE S W.The effect of water absorption on the dielectric properties of epoxy nanocomposites[J].IEEE Transactions on Dielectrics and Electrical Insulation,2008,15(1):106-117.
[11]RAIN P,BRUN E,GUILLERMIN C,et al.Experimental model of a silica/epoxy interface submitted to a hygrothermal aging:A dielectric characterization[J].IEEE Transactions on Dielectrics and Electrical Insulation,2013,19(1):343-351.
[12]LI Y,LI R,HUANG L,et al.Effect of hygrothermal aging on the damage characteristics of carbon woven fabric/epoxy laminates subjected to simulated lightning strike[J].Materials and Design,2016,99:477-489.
[13]ALMEIDA J H S,SOUZA S D B,BOTELHO E C,et al.Carbon fiber-reinforced epoxy filament-wound composite laminates exposed to hygrothermal conditioning[J].Journal of Materials Science,2016,51(9):4697-4708.
[14]DOGAN A,ATAS C.Variation of the mechanical properties of E-glass/epoxy composites subjected to hygrothermalaging[J].Journal of Composite Materials,2015,50(5):637-646.
[15]MOJTABA H Y,PEARL L S.FTIR analysis of a polycarbonate blend after hygrotherm alaging[J].Journal of Applied Polymer Science,2015,132(3):41316.
[16]XIAO G Z,DELAMAR M,SHANAHAN M E R.Irreversible interactions between water and DGEBA/DDA epoxy resin during hygrothermal aging[J].Journal of Applied Polymer Science,2015,65(3):449-458.
[17]KUMAGAL S,YOSHIMURA N.Impacts of thermal aging and water absorption on the surface electrical and chemical properties of cycloaliphatic epoxy resin[J].IEEE Transactions on Dielectrics and Electrical Insulation,2002,7(3):424-431.
[18]赵鹏,熊金平,左禹.湿热环境下介质因素对CF/UPR复合材料的影响[J].化工新型材料,2010,38(1):72-74.
[19]WANG Y,LIU Y,XIAO K,et al.The effect of hygrothermal aging on the properties of epoxy resin[J].Journal of Electrical Engineering and Technology,2018,13(2):892-901.
[20]ADAMSON M J.Thermal expansion and swelling of cured epoxy resin used in graphite/epoxy composite materials[J].Journal of Materials Science,1980,12(7):1736-1745.
[21]王有元,王施又,黄炎光,等.干式变压器环氧树脂热老化特性研究[J].高电压技术,2018,44(1):187-194.
[22]LIU Y,AN Z,CANG J,et al.Significant suppression of surface charge accumulation on epoxy resin by direct fluorination[J].IEEE Transactions on Dielectrics and Electrical Insulation,2012,19(4):1143-1150.
[23]ZHAO X,LIAO R,LIANG N,et al.Role of defects in determining the electrical properties of ZnO ceramics[J].Journal of Applied Physics,2014,116(1):526.
[24]RHAIEM A B,HLEL F,GUIDARA K,et al.Dielectric relaxation and ionic conductivity studies of[N(CH3)4]2Cu0.5Zn0.5Cl4[J].Journal of Alloys and Compounds,2008,463(1):440-445.
[25]LIU Y,AN Z,CANG J,et al.Significant suppression of surface charge accumulation on epoxy resin by direct fluorination[J].IEEE Transactions on Dielectrics and Electrical Insulation,2012,19(4):1143-1150.
[26]ALESSI S,CONDURUTA D,PITARRESI G,et al.Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends.Thermal,mechanical and morphological behaviour[J].Polymer Degradation and Stability,2011,96(4):642-648.
[27]龚瑾,李喆,刘新月.氧化铝/环氧树脂复合材料空间电荷特性与高温高湿环境下交流电场老化[J].电工技术学报,2016,31(18):191-198.