Preparation of Calcium Carbonate from Cockle Shells as Fillers in Natural Rubber

The purpose of this research is to study the preparation of calcium carbonate from cockle shells by precipitation method and compare it to calcium carbonate from high temperature heating, commercial calcium carbonate, and cockle shell powder. The properties of the vulcanized natural rubber mixed with different types of calcium carbonate were observed. It appeared that the precipitated calcium carbonate delivered the best properties (hardness, 300% modulus, tensile strength, elongation at break, tear strength, and abrasion resistance), followed by the high temperature heated calcium carbonate, the commercial calcium carbonate, and the cockle shell powder, respectively. This result corresponded to the morphology from the scanning electron microscope (SEM); the precipitated calcium carbonate had crystalline form and the most uniform particle size, followed by the high temperature heated calcium carbonate, the commercial calcium carbonate, and the cockle shell powder. In particular, the cockle shell powder was composed of large and small particles dispersed over a wide range, which brought about the weak point of vulcanized rubber and caused the lowest properties of the vulcanized rubber mixed with cockle shell powder.