Preparation And Properties Of SEBS-g-MAH Ionomer And Its Modified PP Cable Compound

At present,the main insulation material of high-voltage power cables is cross-linked polyethylene（XLPE）,which has been widely used due to its good electrical and mechanical properties.However,this kind of cross-linked cable has some disadvantages.In the process of preparing this kind of cross-linked cable,high temperature cross-linking is required and energy consumption is high,so it is difficult to recover after reaching the service life,which does not meet the requirements of low carbon and environmental protection.Therefore,in recent years,the research of polypropylene（PP）non-cross-linked cable material instead of XLPE has become a hot spot.The heat resistance of thermoplastic PP is higher than that of XLPE,and its electrical and mechanical properties are excellent.It can be used without cross-linking,with low energy consumption and can be recycled,so it is the best material to replace XLPE.However,the disadvantages of PP such as low melt viscosity and high modulus limit its application,especially the low melt viscosity.In the process of cable extrusion,it is easy to deflect the core and cause uneven distribution of high voltage cable field strength,which is difficult to process,resulting in unqualified cable and high voltage breakdown.How to prepare non-crosslinked PP high-voltage cable material with high melt viscosity is the focus of research.In this paper,hydrogenated styrene-butadiene-styrene block copolymer（SEBS）grafts calcium maleate ionomer SEBS-g-MAca（S-g-MCa）and SEBS grafts magnesium maleate ionomer SEBS-g-MAMg（S-g-MMg）was blended with PP to prepare ionomer-modified PP cable compound PP/S-g-MCa（calcium cable compound for short）and PP/S-g-MMg（magnesium cable compound for short）,and the effects of ionomer and its blends with PP on melt rheological properties,electrical properties and mechanical properties were studied,It lays a solid theoretical and engineering application foundation for the industrialization of non-crosslinked PP high-voltage power cables.Firstly,in this experiment,ionomer was prepared.SEBS grafted maleic anhydride SEBS-g-MAH（S-g-MH for short）was prepared by solid phase grafting,and characterized by IR.The grafting process was optimized by uniform design and the reaction kinetics of SEBS grafted MAH was studied.The results showed that the reaction temperature and time were 92℃and 60min,respectively,and the amount of benzoyl peroxide（BPO）and MAH was 4%and 11%of the mass of SEBS,respectively.At this time,the maximum grafting rate was 3.83 wt%,and the minimum gel content was 0.56 wt%;1781.90 cm^-1in the infrared spectrum is the characteristic absorption peak of carbonyl group,indicating that MAH has been successfully grafted onto SEBS.The kinetic study of SEBS grafting MAH showed that the apparent activation energy at the initial stage of the grafting reaction was Ea=60.69 k J/mol,and the grafting reaction rate was proportional to the 1.062th power of the initiator molar concentration and the 1.613th power of the monomer molar concentration.The grafting kinetic model was Re=Aexp[（-60.69）?（（RT））][M]^1.613[I]^1.062。Secondly,calcium ionomer S-g-MCa and magnesium ionomer S-g-MMg were prepared by blending S-g-MH with calcium stearate and magnesium stearate,and characterized by FTIR and XPS,and their volume resistivity and breakdown field strength were studied.The results showed that the formation of S-g-MCa and S-g-MMg was confirmed by IR and XPS.When the ion content of S-g-MCa and S-g-MMg is 0.8 wt%（S-g-MCa-0.8）and 0.6 wt%（S-g-MMg-0.6）respectively,their comprehensive properties are the best,and the volume resistivity is 3.87×10¹⁴??m and 4.48×10¹⁴??m,the characteristic breakdown value is 22.86 k V/mm and 22.81 k V/mm respectively.Finally,PP was blended with S-g-MCa-0.8 and S-g-MMg-0.6 to prepare PP/S-g-MCa（hereinafter referred to as calcium cable material）and PP/S-g-MMg（hereinafter referred to as magnesium cable material）,and their micromorphology,rheological properties,volume resistivity,dielectric constant,loss angle tangent,breakdown field strength,tensile strength,elongation at break and crystallization behavior were studied.The results show that the spherical structure is found on the section of calcium cable material for the first time by SEM analysis.With the increase of S-g-MCa content,the spherical structure increased,the diameter difference of spherical structure decreases gradually,and the spherical structure was more evenly distributed;However,there was a rod-like structure on the section of magnesium cable material.When the amount of S-g-MMg increased,it was found that the number of rod-like structures on the section also gradually increases,and the distribution was more uniform,and the maximum length also increased to 6.5?m.Observing the POM images of calcium cable material and magnesium cable material,it was found that when the amount of ionomer increased,the spherulites of PP were gradually destroyed,until the spherulites disappeared.For calcium and magnesium cable materials,when the amount of S-g-MCa is 50 wt%and the angular frequency is 0.05 rad/s,the composite viscosity is 26600 Pa·s,and the torque is 4.2 N·m;When the addition of S-g-MMg is50 wt%and the angular frequency is 0.05 rad/s,the composite viscosity is 33300 Pa·s,and the torque is 7.3 N·m.For the electrical and mechanical properties of calcium and magnesium cable materials,when the addition of S-g-MCa is 50 wt%,the volume resistivity is 4.58×10¹⁴??m,breakdown field strength characteristic value is 22.10 k V/mm,dielectric constant is 2.239,loss angle tangent is 0.00675,tensile strength is 13.12 Mpa,elongation at break is 485.94%;When the addition of S-g-MMg is 50 wt%,the volume resistivity is 5.58×10¹⁴??m,the characteristic breakdown field strength is 23.98 k V/mm,the dielectric constant is 2.249,the loss angle tangent is 0.00483,the tensile strength is 13.40 MPa,and the elongation at break is 581.98%.