潮湿环境下二氧化硅掺杂交联聚乙烯的分子动力学模拟
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摘要
为了对比研究水分对交联聚乙烯(XLPE)和SiO_2掺杂交联聚乙烯(SiO_2/XLPE)体系的影响,采用分子动力学方法,建立了含水质量分数分别为0,0.5%和1%的6个XLPE和SiO_2/XLPE模型.采用温度比体积曲线法得出随着水含量的增加,XLPE的玻璃化温度(T_g)依次为273K,258K和251K,而SiO_2/XLPE体系为285K,271K和266K.结果表明掺杂SiO_2提高XLPE的T_g,水分降低两体系的T_g.计算300K下两体系的弹性模量和剪切模量,结果表明水分降低了其机械性能,掺杂SiO_2提高其机械性能.此外,拟合均方位移曲线发现随着温度的上升水分子扩散系数增加,而掺杂SiO_2抑制了水分子的扩散.因为添加SiO_2后其表面羟基与水分子形成氢键,并且水分子自身由于氢键发生团聚而使得水分子聚集在SiO_2周围.研究结果可对XLPE和SiO_2/XLPE体系的微观水树枝现象和老化过程提供参考.
In order to study the effects of water molecules on cross-linked polyethylene(XLPE) and nano-SiO_2 doped XLPE systems,six models with water content of 0,0.5%,and 1% of the amorphous region of XLPE and SiO_2/XLPE were built and simulated by molecular dynamics(MD),and the glass transition temperature(T_g),mechanical properties and the diffusion coefficient of water in XLPE and SiO_2/XLPE have been researched.The T_g of XLPE with water content of 0,0.5%,and 1% is 273 K,258 Kand 251 K,while that of SiO_2/XLPE is 285 K,271 Kand 266 K,respectively.The results show that doping SiO_2 increases T_g of XLPE and water decreases T_g of XLPE and SiO_2/XLPE.The calculation results of the elastic modulus and shear modulus of the two systems at 300 K show that the mechanical properties of these two systems are reduced by water content,and the elastic modulus and shear modulus of XLPE are increased by doping SiO_2,namely,the mechanical properties of XLPE are improved.The diffusion coefficient of water molecule is obtained by fitting the slope of the linear part of the mean shift curve.It is found that the diffusion coefficient of water molecule increases with the increase of temperature.Doping SiO_2 inhibits the diffusion of water molecule.After adding SiO_2,the surface hydroxyl groups form hydrogen bonds with water molecule,and the water molecule aggregates around SiO_2 due to the agglomeration of hydrogen bonds.The research can provide some reference for the understanding of water trees and thermal aging test of XLPE or SiO_2/XLPE.
In order to study the effects of water molecules on cross-linked polyethylene(XLPE) and nano-SiO_2 doped XLPE systems,six models with water content of 0,0.5%,and 1% of the amorphous region of XLPE and SiO_2/XLPE were built and simulated by molecular dynamics(MD),and the glass transition temperature(T_g),mechanical properties and the diffusion coefficient of water in XLPE and SiO_2/XLPE have been researched.The T_g of XLPE with water content of 0,0.5%,and 1% is 273 K,258 Kand 251 K,while that of SiO_2/XLPE is 285 K,271 Kand 266 K,respectively.The results show that doping SiO_2 increases T_g of XLPE and water decreases T_g of XLPE and SiO_2/XLPE.The calculation results of the elastic modulus and shear modulus of the two systems at 300 K show that the mechanical properties of these two systems are reduced by water content,and the elastic modulus and shear modulus of XLPE are increased by doping SiO_2,namely,the mechanical properties of XLPE are improved.The diffusion coefficient of water molecule is obtained by fitting the slope of the linear part of the mean shift curve.It is found that the diffusion coefficient of water molecule increases with the increase of temperature.Doping SiO_2 inhibits the diffusion of water molecule.After adding SiO_2,the surface hydroxyl groups form hydrogen bonds with water molecule,and the water molecule aggregates around SiO_2 due to the agglomeration of hydrogen bonds.The research can provide some reference for the understanding of water trees and thermal aging test of XLPE or SiO_2/XLPE.
引文
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[2]LEWIS T J.[J].IEEE T DIELECT EL IN,1994,1(5):812-825.
[3]张秀敏,蒲孝文,李康,等.[J].绝缘材料,2015,48(10):1-9.
[4]ZHANG L,ZHOU Y,CUI X,et al.[J].IEEE T DIELECT EL IN,2014,21(4):1554-1564.
[5]徐明忠,赵洪,吉超,等.[J].高电压技术,2012,38(3):684-690.
[6]TANAKA T,BULINSKI A,CASTELLON J,et al.[J].IEEE T DIELECT EL IN,2011,18(5):1482-1517.
[7]IEEE.IEEE International Conference on Solid Dielectrics.[C]//LEWIS T J.Interfaces and nanodielectrics are synonymous.July 5-9,2004,Toulouse:IEEE,2004:792-795.
[8]张晓星,陈霄宇,肖淞,等.[J].高电压技术,2018,44(3):740-749.
[9]杨青,兰逢涛,何州文,等.[J].绝缘材料,2015,48(11):40-43,48.
[10]凡朋,周登波,严海健,等.[J].高电压技术,2017,43(9):2875-2880.
[11]MODULE F.Material Studio 6.0[CP].Accelrys inc.,San Diego,CA,2011.
[12]SUN H,REN P,FRIED J R.[J].Comput Theor Polym Sci,1998,8(1/2):229-246.
[13]ANDERSEN H C.[J].J Chem Phys,1980,72(4):2384-2393.
[14]BERENDSEN H J C,POSTMA J P M,GUNSTEREN W F V,et al.[J].J Chem Phys,1984,81(8):3684-3690.
[15]KARASAWA N,GODDARD W A.[J].Macromolecules,1992,25(26):7268-7281.
[16]CHEATHAM T EⅢ,MILLER J L,FOX T,et al.[J].J Am Chem Soc,1995,117(14):4193-4194.
[17]WU C,XU W.[J].Polymer,2006,47(16):6004-6009.
[18]刘曦,蔡钢,濮峻嵩,等.[J].绝缘材料,2016(5):60-64.
[19]YANG Q,CHEN X,HE Z,et al.[J].RSC Adv,2016,6(15):12053-12060.
[20]FOX T G,FLORY P J.[J].J Appl Phys,1950,21(6):581-591.
[21]HE E,WANG S,LI Y,et al.[J].Comput Mater Sci,2017,134:93-99.
[22]NOGUEIRA P,RAMREZ C,TORRES A,et al.[J].J Appl Polym Sci,2015,80(1):71-80.
[23]ZAFAR A,BERTOCCO F,SCHJDT-THOMSEN J,et al.[J].Compos Sci Technol,2012,72(6):656-666.