Structure property relations of copolymerised polypropylene /SiO 2 nanocomposites prepared by solid state shear milling (S 3 M) method

In the present paper, solid state shear milling (S³M) method was used to prepare the copolymerised polypropylene (Co-PP)/nano-SiO₂ composites under the conditions of solvent free and non-organic treatment. The change of phase morphology and arrangement of SiO₂ under mechanical force were firstly observed in the complex multiphase and multicomponent Co-PP/nano-SiO₂ composite. The effect of milling cycles on the phase structure and mechanical properties was studied. It was found that the S³M method was an effective way which can adjust the phase structure of composite through change of milling cycles. After 20 milling cycles, the composite can form a structure with a lot of SiO₂ particles around the ethylene–propylene copolymer phase, the Charpy notched impact strength of the composite with 4 wt-%SiO₂ particles can be largely improved from 24·2 to 38·2 kJ m^–2. While after 30 milling cycles, the composite can form a structure with SiO₂ particles dispersed more uniformly in the Co-PP matrix. However, with this structure, the prepared composite has higher stiffness but the notched impact strength could not be greatly improved. The mechanism of the toughening effect is discussed and the structure property relation established.