Research And Application Of Surface Nano-structured Mineral Powders

Mineral powders have numerous applications in various areas of plastics, textiles, rubbers, adhesives, paints and papers in order to reduce cost and improve properties. Mineral powders are good crystalline, and they break along the cleavage plane when they are comminuted, which cause the mineral powders have flat surfaces and sharp edge angles. Flat surfaces limit contact area and coupling links between the polymer and the powders, and sharp edge angles cause many stress concentration points where breakage always initiate from in the polymer matrix. As a result the composite materials can not have very high performance, and also the filling ratio is limited. How to improve the surface morphology of mineral powders is an important research field these years. This paper has an originated investigation as follows:Mineral powders with nanostructure surface were prepared by chemical method and heterogeneous nucleation in system. Mineral powders such as ground calcium carbonate (GCC), wollastonite, and dolomite were coated with nanometer particles which were calcium carbonate with calcite structure after the surface finish. Mineral powders had better surface morphology after surface finish that the smooth cleavage planes were coated with nanometer particles and the sharp edge angles were blunt by the coating of nanometer particles. The technological parameter of the reaction system such as filling amount of mineral powders, concentration of, mixing intensity had intensive effect on the result of the surface finish. In order to gaining nanostructure surface, appropriate technological parameter should be carefully chosen. Ultrasonic disintegrator and stirred ball mill were employed to check the bond strength between the nanostructure coating layer and the mineral powder matrix, and the result showed that their was a strong bond strength between them for the coating layer still existed without break after disintegrating by large power ultrasonic. The composite mineral powders had larger specific surface area more than original mineral powder with substantial increase of 100~500%. The composite mineral powders also had better whiteness, viscosity and so on, which could wide the application field of mineral powders. Surface pattern of mineral powder, surface structure, system temperature, system value were examined during the course of surface finish, and then analyzed the surface finish mechanics.Composite GCC and wollastonite powders were filled into PP matrix to prepare composite polymer. Mechanical properties of composite PP were tested, and also fracture analysis, XRD analysis; DSC analysis had been done to the composite PP. Test result showed that PP composites filled by composite mineral powders had better mechanical properties. Such as when the filling ratio is 5~10%, the fracture elongation percent of PP filled by composite GCC was greater than PP matrix. When the filling ratio is 30%, the impact strength of PP filled by composite wollastonite was greater than PP filled by wollastonite more than 30%. Composite mineral powders had stronger bond with PP matrix than original mineral power because of their nanostructure surface. PP composite filled by composite mineral powders had higher crystallizing point and big crystallinity. As follows are the mechanics of how PP was toughed and reinforced by composite mineral powders: higher bonding strength between fillers and matrix; small scope deformation is easier to initiate and much energy is need to change to big deformation; PP composites have smaller grains; lots of little size cracks can be initiated and they will change orientation during growth. Composite mineral powders have good application potential in plastics, rubbers and paints for they have advantages of both the micrometer powders and nanometer powders. Now the technology has finished pilot-scale experiments, and has finished technical evaluation by ministry of education with an evaluation of international advanced technology.