超音波探査法を用いた炭酸カルシウム配合ポリプロピレン/エチレン酢酸ビニル共重合体の特性評価
Acoustic Microscopy Evaluation of Polypropylene/Ethylene Vinyl Acetate Filled with Calcium Carbonate
光石一太
Mitsuishi, Kazuta
The agglomerate of particles and voids at the polymer-particle interface and the heterogeneous structure, have been characterized by scanning acoustic microscopy for polypropylene (PP)/ethylene vinyl acetate polymer blends (EVA) filled with modified calcium carbonate (CaCO3). The relationships between the heterogeneous structure and mechanical properties (tensile strength, elongation at break, impact strength) of the PP/EVA/CaCO3 series were investigated.
Using ultrasonic images, the heterogeneous structure in the PP/EVA/CaCO3 series was evaluated based on the binarization method. Polymer blends were prepared by mixing PP and EVA using a two-roll mill, then the PP/EVA mixture and various size CaCO3 particulates were mixed on the same mill. Stearic acid was used as a modifier for CaCO3.
By adding 2wt% EVA to PP, the heterogeneous structure decreased to about one-seventh the value of the PP/CaCO3 blend. Furthermore, the heterogeneous structure in the modified CaCO3 series was about one-thirtieth that of the unmodified blends. The tensile elongation at break depends on the heterogeneous structure, irrespective of CaCO3 size and EVA content. However, it is recognized that impact strength depends on the heterogeneous structure and particle size. The impact strength of PP/ EVA filled with small CaCO3 particulates was greater than that with larger CaCO3 particulates for the same heterogeneous structure.
Key words: Acoustic microscopy / Polypropylene / Ethylene vinyl acetate / Calcium carbonate / Modification