Nano silica(nano-SiO2)was modified by silane coupling agent(KH550)and stearic acid.Then recycled polypropylene(RPP)nanocomposites were prepared by twin-screw extruder melt-blending process.The results show that the modified nano-SiO2 has good hydrophobic and lipophilic properties and a good dispersion effect in the matrix.With the increase of modified nano-SiO2 mass fractions,the melt mass flow rate(MFR)of RPP increases and then decreases.When the mass fraction of modified nano-SiO2is 1%,the MFR reaches the maximum.When the mass fraction of modified nano-SiO2 is only 0.5%,the impact strength of RPP composite reaches the maximum value of 22.23 kJ/m2,which is 134.99%higher than that of unmodified nano-SiO2/RPP with the same mass fraction.With the increase of modified nano-SiO2 mass fractions,the tensile strength of the composites increases first and then decreases.When the mass fraction of modified nano-SiO2reaches 3%,the tensile strength of RPP reaches the maximum value of 20.6 MPa.When the mass fraction of red phosphorus(RP)is20%,and the mass fraction of modified nano-SiO2 is 2%or 3%,the flame retardant level of RPP composites reaches UL94 V-0 level.Through studying the effects of modified nano-SiO2 on the structures and properties of RPP,the valuable references for the high-quality recycling of recycled polyolefin materials are provided.
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