Physical-Mechanical Properties of Chartwell^® Coupling Agent-Treated Calcium Carbonate and Silica-Reinforced Hybrid Natural Rubber Composites

Abstract

In this work investigated the possibility of applying a superficial treatment to ultra-fine calcium carbonate aiming to improve its interaction with the polymer chains of natural rubber so it does not act just as a filler. Commercial processes commonly use 40 phr of Silica as reinforcement filler. Here, we have evaluated the partial replacement of Silica by two types of calcium carbonate into hybrid natural rubber composites, untreated ultra-fine calcium carbonate and with ultra-fine calcium carbonate treated with 2% Chartwell C-515.71HR®. We added calcium carbonate fillers to the composite mixtures (as replacements for commercial silica treated with silane) and studied their influence on the vulcanization process. According to our findings, between 25% and 75% of the silica can be replaced with treated calcium carbonate, and up to 30 parts of CaCO3 can be combined with 100 parts of NR without compromising the properties of the polymer matrix (NR), which generates economic advantages for this industry. Treated calcium carbonate was able to link the inorganic and organic parts of the composite due to its bifunctionality; hence, it can be used as a filler to partially replace silica in hybrid NR composites.

Keywords

• NR-CaCO₃ composites
• vulcanization
• crosslink density
• mechanical properties
• coupling agent