Chemical precipitation route has been demonstrated for in-situ chlorination of polypropylene and structural modification to integrate flame retardancy along with facile processing parameters, i.e. optimum melt flow index and mechanical properties. Thus, obtained chlorinated polypropylene (Cl-PP) was characterized for optimized composition and degree of chlorination, chemical structure, morphology, physical properties with the help of infra-red spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), melt flow index and other standard methods. The analytical results revealed the 74% chlorination of polypropylene chain increased with the molecular weight, comparable melt flow index and improved flame retardancy from V2 to V0 grade on UL-94 scale due to reduced heat release rate and improved limiting oxygen index from 17.5 to 27.1 due to structural changes and induced polycrystallinity. The evolved features of PP were explained on the basis of synergistic interaction, evolved crystallinity, size reduction and functionality during chemical treatments and reprecipitations. Further, the obtained Cl-PP was explored as the coating material for insulation of cables with electric insulation and durable properties.