Properties Of Water Tree Growth And Breakdown In LDPE/MMT Nano-Composite

Organic nano-montmorillonite (Montmorillonite, MMT) is a hot issue in the fieldof nano-dielectric currently. With wide application of Low density polyethylene (LDPE)in extra high voltage gird, research of LDPE with excellent dielectric property and heatresistant performance is of great academic significance and application value.Preparation method of LDPE/MMT nano-composites and experiment design of watertree propagation are studied and a type of LDPE/MMT nano-composites was prepared.Comparison of trigger and growing properties of water trees in LDPE and LDPE/MMTnano-composites was illustrated through contrast experiment. Then breakdownperformances of LDPE and LDPE/MMT nano-composites were tested as well. Themain works of the author are as follows：①LDPE/MMT nano-composites were prepared by in melt intercalation process.Intercalation behavior and microstructure of composites of MMT in LDPE areinvestigated by using X-ray diffractometry(XRD) and transmission electronmicroscopy(TEM) and intercalation effect of MMT in polymer is also analyzed.Thermal and mechanical properties tests show that heat resistant performance andtensile strength properties of LDPE/MMT nano-composites are improved comparedwith LDPE.②Experiment platform of water tree growing is established based on the waterneedle model and then growing morphology of water trees in the nano-composites wereobserved under a constant voltage. Length of the water trees is measured and the triggerrate is counted. Analysis of the impact of MMT nano-particles on the water absorptionand water trees growth is also given. Results show that nano-montmorillonite particlescould effectively improve the degree of crystallinity of the LDPE and reduce its grainsize. Besides, nano-montmorillonite particles also reduce water absorption to inhibit thewater tree growth in nano-composites.③Pilot study of the breakdown performance of LDPE and LDPE/MMTnano-composite were made, the breakdown characteristics of LDPE/MMTnano-composite after water tree aging experiments were also studied.Compared andanalyzed different percentage content of MMT nano-particles impact on thebreakdown strength of LDPE of in water tree aging process.Experimental analysis ofbreakdown strength for the LDPE and LDPE/MMT nano-composite shows that the different addition of the MMT could improve the average breakdown strength andWeibull breakdown strength of LDPE materials.