Improvement of physico-mechanical properties of calcium carbonate filled natural nubber and low density polyethylene blends with titanate coupling agent

Nonblack particulate fillers most used with thermoplastic and rubber are calcium carbonate, silica, talc and alumina hydrates. The main characteristics, which control the effectiveness and the dispersion of filler in the polymer, are structure, surface area and chemical activity of filler. The mechanical behavior of rubber-thermoplastic blends depends greatly on interactions and compatibility that develop between the two polymers and the filler. The main objective of this study is to improve physico-mechanical properties of calcium carbonate (CaCO₃) filled natural rubber (NR) and low density polyethylene (LDPE) blends using a titanate coupling agent. Two series of NR/LDPE blends, with and without titanate coupling agent, were prepared by varying LDPE loading from 10% to 90% at 10% intervals. 20 parts by weight of CaCO₃ per 100 parts of combined polymer was incorporated into every blend composition. The blends were prepared using a Brabender plasticorder by melt mixing at a temperature of 130 °C, and at a rotor speed of 60 rpm. Physico-mechanical properties such as tensile properties, hardness, tear strength and morphology of the blends were studied. These properties were determined according to ISO standards. Morphology of the tensile fracture surface of blends was observed using a transmitted light microscopy. Tensile strength, tear strength and hardness of NR/LDPE blends increase with increase in LDPE loading while elongation at break decreases. NR/LDPE blends with titanate coupling agent exhibited enhanced properties at every LDPE loading. NR/LDPE blends having 30% of LDPE loading showed highest tensile strength. In this blend, NR was dispersed in LDPE matrix with good adhesion between NR and LDPE.