Research On LDPE/SiO_x Nanocomposites Based On The Organic Silicon Sol

The technology for synthesizing polyolefin nanocomposites has becomeglobal research hot spot. Polyolefin nanocomposites which have perfect perform-ance, especially those with good electrical properties, are widely applicated tothe electrical field. Preparation of nanocomposites, especially polyethylene-basednanocomposites, is very difficult because of the small particle size of nanoparti-cles being easily to agglomerate. Acodingly this, on the basis of the high boilingpoint organic silicon sol preparation process, we explore the new of LDPE/SiO_xnanocomposite materials and research their mechanical properties and dielectricproperties. This work has laid a solid foundation for large-scale industrial produ-ction of high performance PE nanocomposites.The high-boiling point organic silica sol was prepared by alcoholysis withtetraethoxysilane (TEOS) and home-made reagent N. The factors and levels oforthogonal experiment are determined by single factor experiment by whichinvest the influence factors including ratio (reagent N and TEOS molar ratio),reaction temperature and reaction time on solid content of the organic silica sol.Orthogonal experiment was designed. The optimum conditions for preparation ofhigh boiling point organic silica sol was determined by analysising of the resultsof orthogonal experiment. The results showed that a transparent high-boilingpoint organic silica sol, which solid content is about39wt%, temperature rangeof volatile volatilization is130℃to170℃and the stable time in eight months ormore, were successfully prepared by the use of alcoholysis.For the first time, LDPE/SiO_xnanocomposite materials were prepared byblending high boiling point organic silica sol with molten low density polyethyle-ne directly. The factors (content of SiO_x, mixing time, speed, temperature etc)were performed by uniform design method. Tensile strength and elongation atbreak were used as the mechanical properties evaluation indicators and breakd- own strength and volume resistivity were used the electrical properties evaluation.Preparation of LDPE/SiO_xcomposite blend technology has been identified bystatistical analysis of experimental results. Farther more, the nanocompositeswhich SiO_xparticle size was55nm-96nm were successful prepared.The results showed that the SiO_xnanoparticles could effectively reduce thespace charge density of the material. The impacts of the SiO_xcontent of LDPE/SiO_xcomposites were researched, such as processing rheology, mechanical pro-perties, the space charge distribution, electrical tree discharge, the breakdownfield strength and volume resistivity. When added to the SiO_xnanoparticles, theelectrical tree inception voltage of composite materials increased to11.25kV andinhibited the growth of electrical tree. The volume resistivity of LDPE/SiO_xnanocomposite compared to LDPE increased by82.6%. At the same time, thematerial’s breakdown field strength, tensile strength, elongation at break andelastic modulus had been varying degrees of improvement.