Study On Mechanical And Electrical Performance Of Acetylated SEBS/PP Composites

Polypropylene(PP)is expected to become a substitute for crosslinked polyethylene(XLPE)insulation because of its outstanding electrical performance and environmentally friendly characteristics.The blending of thermoplastic elastomers into polypropylene can improve its low-temperature brittleness problem,making it have great potential for application in high voltage(HV)cable insulation.However,after a large amount of thermoplastic elastomer is incorporated,the electrical resistance of PP will be reduced,resulting in it not being able to meet the electrical requirements of HV cables.In order to solve this problem,in this paper,the acetylation reaction is used to introduce acetyl groups in the styrene counterpart of the terminal segment of thermoplastic elastomer styrene-ethylene-butadiene-styrene(SEBS)without damaging its macromolecular chain,and to produce acetophenone groups,so that SEBS has the effect of both a toughening agent and a voltage stabilizer.The melt blending of acetylated SEBS(Ac-SEBS)with PP not only enables PP to have excellent mechanical and electrical properties at the same time,but also solves the problem of easy migration of acetophenone small molecules due to incompatibility with polymers.In this paper,the mechanical properties and electrical insulation properties of AcSEBS/PP are mainly investigated with reference to PP and SEBS/PP.The results show that Ac-SEBS has an acetophenone structural unit on Ac-SEBS.When 30% of Ac-SEBS was incorporated into PP,Ac-SEBS had relatively good dispersion in the polypropylene matrix when the acetylation degree is not high.Moreover,Ac-SEBS/PP has relatively good thermal stability.In terms of mechanical properties,the highly flexible Ac-SEBS can maintain the toughening effect of SEBS,significantly increase the tensile strength and elongation at break of PP,and reduce the elastic modulus of PP.In addition,the loss factor of Ac-SEBS/PP does not exceed 0.2,and the thermal elongation is only 10%.It shows that Ac-SEBS/PP has excellent mechanical properties and meets the industrial requirements of HV cable applications.In terms of electrical performance,the acetophenone structural unit on Ac-SEBS absorbs high-energy electrons to significantly increase the alternating current(AC)and direct current(DC)breakdown field strength of the composite system and inhibits the growth and growth of electrical branches.Ac-SEBS/PP with 4.6% acetylation had higher AC and DC breakdown strength than other composites and slightly higher than pure PP.Compared with SEBS/PP,Ac-SEBS/PP has a 22.4% increase in DC breakdown field strength and a 37.1% increase in treeing voltage.At this time,AcSEBS can also make electrical tree branches grow in a jungle-like shape to inhibit the spread of electrical tree branches.Ac-SEBS with high electron affinity can also reduce the carrier mobility by trapping electrons so that the electrical conduction current of SEBS/PP is reduced,and by introducing deep traps,it can suppress the accumulation of space charge to a certain extent,thereby improving Insulation performance.In addition,the dielectric loss factor of Ac-SEBS/PP under power frequency conditions does not exceed 0.001,which is within the scope of engineering.Therefore,AcSEBS/PP composites have excellent electrical insulation performance and mechanical performance at the same time and are promising for replacing XLPE as the material for the main insulation in HV cables.