Research On SEBS/PP Halogen-free Cable Material

As a new type of thermoplastic elastomer,styrene-ethylene/butylene-styrene block copolymer(SEBS),which also known as "the fourth generation of rubber",is widely used in wire and cable,automobile and other fields.However,the application of SEBS is limited due to its the poor compatibility with polar materials,high melting viscosity and easy combustion and dripping.Therefore,SEBS modification has become one of the research hotspots.In this paper,the SEBS was grafted with MAH and modified by blending in order to prepare the halogen-free flame retardant cable materials with good comprehensive properties to meet the demand of high performance cable.In this paper,MAH grafting SEBS(SEBS-g-MAH)was prepared by melting in mixer.The influence of MAH dosage,DCP dosage,reaction temperature,reaction time and rotor speed on grafting ratio of SEBS-g-MAH were also investigated in this paper.The grafting formula and technology were determined to obtain the products with high grafting degree.The structure of grafted products was characterized by IR and the grafting rate of SEBS-g-MAH was calculated by acid-base titration.The results showed that the grafting rate of the product increased first and then decreased with the increase of the amount of MAH as well as the blending time and the rotation speed.when the proportion of SEBS,MAH and DCP is 100:3:0.1(phr),the temperature was 175 ?,the rotation speed was 40r/min and the reaction time was 9min,the grafting ratio was 3.18 wt %.The ratio of polymer matrix is determined by testing the mechanical properties.The results showed that the optimum mechanical properties of the polymer matrix are obtained when the ratio of SEBS to PP is 1:1(mass ratio),and the ratio of SEBS503 T to SEBS604 is 3:4(SEBS603T/SEBS503T).The effect of flame retardant and synergistic agent on the fire retardancy,carbon layer after combustion,thermal stability and mechanical properties were investigated by the oxygen index testing,scanning electron microscope(SEM),thermogravimetric analysis(TGA)and tensile testing.The results showed that theoxygen index of the composites increased from 30 to 32 with the change of ratio of montmorillonite to silicone powder and the increase of the amount of montmorillonite and silicon powder.The carbon layer becomes more dense,the thermostability gets better,the tensile strength increased from 7.2 MPa to 9.65 MPa and the elongation at break increased from 752.6 % to 825.6 %.The oxygen index of the composites increased from 29 to 33 with the change of the ratio of MCA to aluminum diethyl phosphinate and the increase of the amount of them,the foaming carbon layer of the composites was formed and thermostability of the composites increased gradually,meanwhile the tensile strength and elongation increased evenly.The oxygen index of the composites with the addition of SEBS-g-MAH increased from 33 to 35,the tensile strength increased from 10.03 MPa to 11.45 MPa,the elongation at break increased from 898.36 % to 910.32 %,and the equilibrium torque at melting was reduced,compared with the sample without SEBS-g-MAH.The electrical properties and water resistance of SEBS/PP flame retardant composites were investigated.The results showed that the volume resistivity was greater than 1.0 × 1010 ? · m,the breakdown field strength is greater than 20 k V/mm,and the water resistance is good,which meet standards for cable requirements(JB/T10707-2007);the effects of antioxidants on the flame retardancy and thermostability of SEBS/PP composites were also researched.The flame retardancy and thermal stability of the composites were improved with the increase of antioxidants.