| Cross-linked polyethylene（XLPE）is widely used in the field of wire and cable due to its excellent electrical properties,mechanical properties and heat resistance.Because it is a thermosetting material,it is difficult to recycle,has a long process flow,and consumes massive large energy,so it is imperative to replace XLPE.As a thermoplastic material,PP has enough mechanical and electrical properties.It is heat-resisting without cross-linking and can be reuse.It is an ideal material to replace XLPE.However,PP itself has some disadvantages such as flammability and insufficient mechanical properties,which limit its application field.Therefore,the modification of PP to prepare flame retardant PP cable materials have attract people’s attention.Based on this,the SBS-g-MAH was prepared as the compatibilizer in this paper,the PP/SBS-g-MAH/SBS dynamic vulcanization and flame retardant material with excellent comprehensive performance were prepared by dynamic vulcanization.The micro morphology,mechanical properties,electrical properties and flame retardant properties of cable material were studied,laying a solid foundation for the preparation of non cross-linked PP flame retardant cable materials.In this paper,SBS-g-MAH was prepared by solid-phase grafting firstly.The optimum conditions of SBS grafting MAH was determined by orthogonal experiment.The structure was characterized by IR spectroscopy,and the grafting kinetics of SBS solid-phase grafting MAH was investigated.The results showed that the optimum conditions of SBS grafting MAH were as follows:temperature 80℃,BPO dosage 1.4wt%,reaction time 120 min,MAH dosage 6 wt%,xylene dosage 5 wt%,the grafting rate of SBS-g-MAH was 2.2%.The characteristic absorption peak of carbonyl group appeared at 1733 cm-1according to infrared spectrum,the MAH was grafted onto SBS.The grafting rate was proportional to the 0.91 power of MAH concentration and 0.46power of BPO concentration.It’s activation energy was 24.36 k J/mol.Then the PP/SBS-g-MAH/SBS matrix material was prepared by dynamic vulcanization.The optimal conditions were determined by the effect of vulcanizing technology on mechanical properties.The change of PP/SBS-g-MAH/SBS dynamically vulcanized were studied by IR spectroscopy.The results showed that with the increase of vulcanizing temperature,rotational speed and SBS content,the mechanical properties of the matrix materials first increase and then decrease;With the increase of DCP content,the mechanical properties of the matrix materials first decreased,then increased,at last decreased.When the vulcanizing temperature was 180℃,the rotational speed was 40 r/min,the SBS dosage was 20 wt%,and the DCP dosage was 0.3 wt%,the composite had the best comprehensive properties,the elongation at break was 488.13%,the tensile strength was 19.71 MPa,the fracture work was 15.49 J.The absorption peak of the C=C double bond in the SBS at 1599 cm-1and 1641 cm-1in the infrared spectrum almost disappeared,indicating that the double bond was opened and cross-linked in SBS.Finally,the mechanical properties,electrical properties and flame retardancy of PP/SBS-g-MAH/SBS dynamically vulcanized flame retardant cable materials with different grafting rate and dosage were studied.The results showed that with the increase of SBS-g-MAH grafting rate and dosage,the mechanical properties,breakdown field strength and flame retardancy of the cable material first increased and then decreased,the volume resistivity decreased first and then increased at last decreased with little change,the dielectric constant and loss tangent had a certain increase.When the SBS-g-MAH grafting rate was 1.76%and the dosage was 4 wt%,the tensile strength,elongation at break and the fracture work were 17.66 MPa,258.18%and 9.47 J,respectively,The volume resistivity was 1.11×1013Ω·m,the dielectric constant and loss tangent were 3.239 and 0.0408 respectively,breakdown field strength was 24.55 k V/mm,the oxygen index（LOI）was 30.8%,and vertical combustion was V-0 level. |
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