Effects of Filler Mixing Methods on Properties of Polypropylene/Talc/Calcium Carbonate Composite Materials

Various mixing methods (①PP→Talc/CaCO3 mixing, ②PP→Talc→CaCO3 mixing, ③PP→CaCO3→Talc mixing) on the mechanical, thermal properties have been characterized by scanning electron microscopy (or acoustic exploration) and differential scanning calorimeter (DSC) .Stearic acid was used as a modifier for CaCO3. PP and Talc (or CaCO3) were mixed on a two-roll mill and thin films were prepared by compressing the mixed compound in a heated press. For mixing method① or ②, the impact strength, tensile strength, tensile elongation at break were more than those of mixing method③. The heterogeneous structure such as aggregation or agglomeration of filled particles and presumably voids at polymer-filler interface for mixing method① or ②, which is calculated by ultra-sonic images, was less than that of mixing method③. In these experiments, impact strength of PP/Talc/CaCO3 composites could roughly be expressed as a function of aggregation or agglomeration fraction. DSC properties (crystallization temperature, melting point, melting enthalpy, etc.) were not remarkably dependent on each mixing method, except for crystallization enthalpy under a cooling crystallization process.