Preparation And Properties Of PP-g-MAH Ionomer And PP Blend For Cable Materials

In the power grid,high-voltage power cables are the key part of primary power transmission,and they play an important role in the safe and stable operation of power loads.At present,the insulating material widely used in high-voltage cables is mainly cross-linked polyethylene(XLPE).However,in the manufacturing process of XLPE cables,the extrusion and cross-linking production process is complicated,energy consumption is high,and polar small molecules are cross-linked.By-products need to be degassed to reduce their content.The more important problem is that XLPE cables are thermosetting materials.After reaching the end of their service life,they are difficult to recycle and cause serious damage to the environment.Therefore,it is imperative to study alternative materials for XLPE.Polypropylene(PP)has high heat resistance,its use temperature can reach 100?without cross-linking,and it has good electrical insulation properties,mechanical properties and high cost performance,so it is considered to be the first choice for XLPE replacement However,the shortcomings of PP itself,such as high modulus and low melt viscosity,limit its application fields,especially the low melt viscosity.Due to gravity during cable processing,eccentricity is likely to occur,which will cause the electric field distribution of high-voltage cables.Unevenness shortens the service life of the cable and even leads to partial breakdown of the cable.Therefore,the preparation of PP high-voltage cable materials with high melt viscosity has become a research hotspot.Based on this,using the characteristics of ionomer to increase viscosity,this paper uses polypropylene grafted maleic anhydride(PP-g-MAH)ionomer and PP blending to prepare PP/polypropylene grafted calcium maleate(PP-g-MACa)and PP/polypropylene grafted with magnesium maleate(PP-g-MAMg)to increase the melt viscosity of PP,and to study its rheological properties,lay a good foundation for the industrialization of PP non-crosslinked high-voltage cables.In this paper,the preparation of ionomers is carried out first.PP-g-MAH was prepared by solid-phase grafting,and the process was optimized by uniform design,and its structure was characterized by infrared spectroscopy.At the same time,the grafting kinetics of PP-g-MAH was studied.The results show that when the temperature is 95?,the reaction time is 60 min,the amount of benzoyl peroxide(BPO)is 4 wt%of PP,and the amount of maleic anhydride(MAH)is 8 wt%,the maximum grafting rate is 4.12%,there is basically no degradation side reaction;the infrared spectrum shows that there are absorption peaks of carbonyl groups at1781.90 cm^-1and 1857.11 cm^-1,indicating that MAH is connected to PP;the PP-g-MAH grafting kinetics model is established.The scientific results show that the grafting rate at the initial stage of polymerization is approximately proportional to the 1.08 power of the initial concentration of the initiator,and is proportional to the power of 1.42 with the initial concentration of MAH,and the apparent activation energy of the PP-g-MAH grafting reaction is Ea=37.75 k J/mol.At the same time,PP-g-MACa and PP-g-MAMg were prepared by blending PP-g-MAH with calcium stearate and magnesium stearate,and their structures were analyzed by infrared spectroscopy and X-ray photoelectron spectroscopy(XPS).Characterization,and the volume resistivity,dielectric properties,breakdown field strength,and mechanical properties of PP-g-MACa and PP-g-MAMg were studied at the same time.The results show that:PP-g-MACa and PP-g-MAMg both have a characteristic peak of carboxylate at 1560 cm^-1;XPS shows that the binding energy of Ca 2p has changed from 347.4 e V to 346.8 e V and the binding energy of Mg 1s has changed from 1303.5 e V to 1302.6 e V,which also proves the formation of ionomers;for PP-g-MACa ionomer,with the increase of Ca²⁺content,the volume resistivity and breakdown field strength of PP-g-MACa first decrease,then increase and then decrease.The dielectric constant first increases,then decreases,and then increases.The dielectric loss first increases and then decreases,the tensile strength first decreases and then increases,the elongation at break first increases and then decreases;PP-g-MACa-0.8 has the best overall performance,and its volume resistivity is 5.29?10¹⁴??m,the characteristic breakdown value is 24.48 k V/mm;for PP-g-MAMg ionomer,with the increase of Mg²⁺content,the volume resistivity of PP-g-MAMg first increases and then decreases,and the breakdown field strength First decrease,then increase,and then decrease,the dielectric constant and dielectric loss both increase first and then decrease,the tensile strength first decreases and then increases,the rate of change of elongation at break first increases and then decreases;PP-g-MAMg-0.8 has the best overall performance,the volume resistivity is7.42?10¹⁴??m,and the characteristic breakdown value is 24.88 k V/mm.The blending of PP and ionomer was further studied.PP/PP-g-MACa and PP/PP-g-MAMg were prepared by blending PP with PP-g-MACa-0.8 and PP-g-MAMg-0.8.At the same time,the morphology,rheological properties,volume resistivity,dielectric properties,breakdown field strength and mechanical properties of PP/PP-g-MACa and PP/PP-g-MAMg were studied.The results showed that there was a spherical structure in the cross section of PP/PP-g-MACa for the first time through the analysis of the morphology and structure by SEM,The spherical structure increases with the increase of Ca²⁺content,and the diameter decreases.There is a rod structure in the section of PP/PP-g-MAMg.The rod structure increases with the increase of Mg²⁺content,and the length diameter ratio and size increase.Through the further analysis of element distribution by energy dispersive spectrometer(EDS),it is found that the distribution of magnesium in PP/PP-g-MAMg is more uniform than that of calcium in PP/PP-g-MACa.With the increase of PP-g-MACa and PP-g-MAMg content,the composite viscosity,storage modulus and loss modulus of PP/PP-g-MACa and PP/PP-g-MAMg increased;When the Ca ionomer content of PP/PP-g-MACa was 70 wt%,the composite viscosity increased the most,the volume resistivity increased by 70.4%,the characteristic breakdown value increased by 3.08%,the tensile strength was 22.13 MPa and the elongation at break was 270.87%;PP/PP-g-MAMg has the best comprehensive properties when the content of Mg ionomer is 30 wt%,the composite viscosity increases the most,the volume resistivity increases by 110.3%,the characteristic breakdown value increases by 4.58%,the tensile strength is 20.44 MPa and the elongation at break is 228%;The comprehensive test of PP/PP-g-MACa and PP/PP-g-MAMg cable insulation materials shows that their tensile strength,elongation at break,volume resistivity and aging properties meet the requirements of GB/T110171-2002 standard.