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Three polypropylene (PP) matrixes with different intrinsic toughness were used to study the morphologies and mechanical properties of PP filled with four sizes of calcium carbonate particles. PP1 was a homopolymer, PP2 was a propylene-ethylene copolymer, and PP3 was a mixture of PP1 and PP2 (PP1:PP2 ‫؍‬ 1:1, weight ratio). Calcium carbonate (CC25, CC4, CC1.8, and CC0.07) with an average particle size of 25, 4, 1.8, and 0.07 m, respectively, was used. It was clear that the PP matrix and filler size had key effects on improvement of mechanical properties of PP matrix. For all three PP matrixes, the yield strength, the flexural strength and modulus of the composites filled with CC25, CC4, and CC1.8 could be regarded as the same. But the yield strength, the flexural strength and modulus of composites filled with CC0.07 were obviously lower than those of composites filled with other sizes of particles. Among four sizes of calcium carbonate particles, CC0.07 had the best toughening effect to improve the impact strength of PP matrix, and the toughening effect of CC0.07 was influenced by PP matrix. For all PP matrixes, only in the case of moderate matrix toughness (PP3 matrix), the composite could receive the highest extent of toughness increase (4.3 times that of matrix). With regard to all PP composites, the best combination of properties was PP2 nanocomposite filled with 20 wt% CC0.07. POLYM. COMPOS., 27:443-450, 2006.

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