Polypropylene toughened with calcium carbonate mineral filler

Abstract

A polypropylene homopolymer was modified by a rigid filler consisting of three different sizes of CaCO₃ particles in various volume fractions. The materials were characterized by differential scanning calorimetry. Mechanical properties of extrusion blended/injection molded samples, including tensile, flexural, Dynatup impact energy and notched Izod impact energy, were examined as a function of temperature down to—40°C, filler particle size, and filler volume fraction.

Dynatup impact tests were performed for compression molded plastic parts. The toughening mechanism of PP homopolymer through the incorporation of calcium carbonate depends on the filler particle size and volume fraction. The toughness of the CaCO₃ filled materials increased significantly at ambient temperature for both material samples and molded plastic parts. A similar improvement was demonstrated in Dynatup and Izod impact tests at low temperatures down to—40°C. The level of toughness increase achieved by the addition of CaCO₃ is close to the toughness produced using rubber at 23°C, and even better at lower temperatures.

Key words:

• Polypropylene
• Calcium carbonate
• Mineral filler
• Toughness