Preparation,Surface Modification And Polypropylene Filled With CaCO₃/wollastonite Composite Particles

Wollastonite is a kind of mineral raw material,with a wide range of scientific and industrial applications of calcium silicate,has been used in biomedical,agricultural,construction,plastic and other fields.Due to the interface compatibility between Wollastonite filler powder and polymer matrix is usually insufficient,modification of wollastonite is required.In this paper,the composite particles of CaCO₃/Wollastonite（W@C）were prepared by coating nano-calcium carbonate on the surface of wollastonite with calcium oxide by homogeneous precipitation method.The CaCO₃/wollastonite composite particles were also organically modified by wet method,and finally the composite material was prepared by filling the powder with different interface characteristics into PP.CaCO₃/Wollastonite composite particles were prepared by homogeneous precipitation method,（1）When the Cao addition was 25%,the carbonization temperature was 15°C,the CO₂ flow rate was 0.08 m³/h,the agitator rotation speed was 400 r/min,and the PEG content dosage was 4.37 g/L,CaCO₃/Wollastonite composite particles with specific surface area of 15.28 m²/g were obtained.（2）Compared with wollastonite particles,CaCO₃/wollastonite composite particles are coated with a layer of CaCO₃particles with an average particle size of 33 nm,and the original sharp edges and angles have been passivated,and the specific surface area is increased by more than 500%.The results of wet organic modification of CaCO₃/Wollastonite composite particles showed that（1）The modification effect of Sodium stearate was better than that of Zinc stearate,the maximum contact angle and activation index of the composite particles were121.156°and 99.8%,respectively,when the Zinc stearate dosage was 2%,the modification time was 20 min,the modification temperature was 60°C and the slurry concentration was 5%.The Zinc stearate are attached to the surface of the CaCO₃/Wollastonite composite particles by physical action.（2）The effect of KH-570 was better than that of KH-570.The dosage of KH-570 was 4%,the modification time was 50min,the modification temperature was 60°C and the slurry concentration was 10%,the contact angle and activation index of the modified composite particles were 94.541°and90.9%respectively.KH-570 was chemically bonded to the surface of the composite particles.The Wollastonite/PP composites with different interface properties were prepared by melt blending method with 20%of the fillers,The results showed that the mechanical properties of W@C/PP composites modified by the four modifiers were improved compared with pure PP and wollastonite/PP composites.The tensile strength,impact strength and flexural strength of W@C/PP composites modified by Zinc stearate were25.19 MPa,10.13 MPa and 80.15 MPa,respectively,which were 53%,36%and 84%higher compared with pure PP,indicating that the mechanical properties of W@C/PP composites modified by inorganic and organic composite were better.