Various properties of composite materials containing grafted mica were studied. These modified mica were used to reinforce HDPE and PP Tensile strength, impact istrength, and modulus of the grafted mica composites are improved rather than silane coupling agent-treated mica composite. The dynamic mechanical properties, the storage modulus E''of grafted mica composite are increased more than silane treated mica system and tan δ_max are decreased. Crystallinity of these composite are found to be increased in following order mica vinyl-silane treated mica