Investigation Of Dielectric Properties Of ZnO/LDPE Composites With Different Particle Sizes

Polyethylene has excellent electrical and mechanical properties,and is widely used as insulation material for power equipment.However,with the introduction and implementation of the global Internet strategy,the demand for long distance and high voltage transmission forms is increasing.Therefore,the insulation performance of the equipment also needs to be improved correspondingly.Many scholars have shown that the properties of polyethylene can be improved by adding inorganic additives to polyethylene to prepare the corresponding composites.However,since the concept of composite materials is put forward,although there are many related research,the relationship between the mesoscopic shape and the macro performance still needs to be explored.Therefore,by adjusting the microstructure and testing the corresponding macroscopic properties,we can further reveal the relationship between the two,which is of great significance for the development of new dielectric materials with better performance.In this paper,low density polyethylene(LDPE)is used as the research object of matrix,9nm,30 nm,100nm,200 nm and 1?m tested five different sizes of Zinc Oxide(Zn O)as an additive in the same way and contents were added to the micro nano composite into LDPE,through two steps of melt blending were prepared by different the particle size and micro nano Zn O/LDPE composite material.Scanning electron microscopy(SEM)was used to observe the particle size and morphology of various Zn O particles,and to observe the dispersion of Zn O in the composites.The crystallization behavior of the composites was tested by differential scanning calorimetry(DSC).The results show that the Zn O particles play the role of hetero nucleation in the composite and increase the crystallinity of LDPE,and the smaller the particle size of Zn O,the more significant the lifting effect is.The AC and DC breakdown properties of LDPE and the composites are tested,and study the relationship between the specimen thickness and breakdown strength in the experimental results,DC and AC breakdown strength of composites with Zn O particle size increasing increased first and then decreased,only when the Zn O particle size is less than 100 nm,breakdown the field of composite material is higher than the breakdown strength of LDPE,Zn O and particle size of 30 nm is the highest breakdown strength;the breakdown field strength of micro nano composites is between the corresponding micro and nano composite materials.On the other hand,with the increase of thickness,the AC breakdown field strength of all composites decreases,but the smaller the particle size is,the smaller the thickness of the composites is,and the dispersion of the breakdown field strength of all composites is also improved.The DC conductance and dielectric spectrum of LDPE and Zn O/LDPE composites are also measured.The results showed that electrical conductivity of LDPE and composites increased with the increase of electric field intensity and temperature,and the electrical conductivity between different particle sizes increased with the increase of particle size.The dielectric spectra of composite materials,in addition to the 9nm size of Zn O/LDPE composite dielectric constant is less than LDPE,the dielectric constant of composite materials were more than LDPE,and the particle size increases,the dielectric constant is large;in addition,the dielectric loss of the composites tangent in the whole frequency range is greater than LDPE.