Study On Preparation And Properties Of PP-based Thermoplastic Semiconductive Inner Shielding Materials

The cross-linked polyethylene cable material is difficult to recycle after reaching the service life,resulting in waste of resources and environmental pollution,which has caused widespread concern.The current research on environmentally friendly recyclable cable materials has become an urgent solution.Polypropylene has become an alternative to cross-linked polyethylene cable insulating material of choice,owing to its excellent electrical insulating,easy processing,excellent mechanical properties,high heat resistance etc.However,few studies have been reported on the non-crosslinked semi-conductive inner shielding materials,that it is of great significance to study the thermoplastic semi-conductive inner shielding materials.This paper first studied the preparation of maleic anhydride grafted polypropylene,and the best preparation process and proportioning were determined.The results show that when the temperature of mixing was 190?,the time was 10 min,the rotating speed was 80r/min and the formula proportion was PP: MAH: St: DCP = 100: 3: 3.2: 0.3,the grafting rate was the largest,0.79 %.Second,the effect of blending process on the volume resistivity of the thermoplastic semi-conductive inner shielding material was explored.The results show that the loading order has a significant effect on the volume resistivity of the system.The volume resistivity of the thermoplastic semi-conductive inner shielding material prepared by the step-by-step feeding method,i.e.mixing resin and then adding carbon black(CB),20.9 ?·cm,was less than 25.1 ?·cm of onestep method.Mixture of time,temperature,rotor speed on the system volume resistivity have a certain impact.With the extension of mixing time,the volume resistivity first decreases and then increases.When the mixing time was 20 min,the volume resistivity is the minimum 17.37 ?·cm.With the increase of temperature,the volume resistivity first decreases and then increases.When the mixing temperature was 200?,the mixing effect was the best,and the volume resistivity is the smallest.With the increase of rotation speed,the volume resistivity first increases and then decreases.When the rotation speed is 40 r/min,the volume resistivity is the smallest.The effects of the amounts of PP-g-MAH,SEBS,and CB components on the properties of the thermoplastic semi-conductive inner shielding material were investigated.The results show that the PP-g-MAH content,the SEBS oil-in-oil ratio,the amount of carbon black and the lubricant dosage affect the performance of the thermoplastic semi-conductive inner shielding material.With the increase of PP-g-MAH dosage,shielding material processing fluidity,the adhesion to copper enhanced,the volume resistivity gradually increased.When PP-g-MAH and PP ratio is 2/3,the balance torque of shielding material is 11.3N·m,the bonding strength with metal is 43 MPa,the volume resistivity is 92.3 ?·cm.With the increase of white oil and SEBS ratio,The volume resistivity of the semiconductive inner shielding material firstly decreases sharply and then tends to be stable.The processing fluidity and the surface smoothness of the composite material increase,and the thermal elongation slightly increases.When the white oil and SEBS oil-filling ratio is 1,the volume resistivity at room temperature 23.92 ?·cm,and the torque at equilibrium is 11.1 N·m.As the amount of carbon black increases,the volume resistivity decreases,the thermal elongation decreases,and the processing fluidity deteriorates.When CB content wsa 30wt%,the volume resistivity is 85.17 ?·cm,the thermal elongation at 20? was 11.3%,the permanent deformation is 5.26% and the balance torque was 7.9 N·m.When the amount of lubricant is 0.6 wt% the shielding material is of the best performance.