Processing characteristics of low‐density polyethylene filled with calcium carbonate of different size distributions

Low‐density polyethylene (LDPE) was filled with blends of different proportions of two sizes of calcium carbonate (CaCO₃; 600 and 2500 mesh). The torque of the LDPE/CaCO₃ samples was measured with a torque rheometer. The results showed that the process torque values of the LDPE/CaCO₃ samples obviously decreased when LDPE was filled with a blend of two sizes of CaCO₃ (600‐ and 2500‐mesh CaCO₃ blend) in comparison with samples filled with CaCO₃ of a single size (600 or 2500 mesh). When the ratio of 600‐mesh CaCO₃ to the total CaCO₃ was in the range of 40–60 wt %, the lowest torque value of the LDPE/CaCO₃ samples was achieved. When the content of CaCO₃ in a sample was 30 wt %, LDPE filled with CaCO₃ of different size distributions showed the largest decrease in the torque ratio in comparison with the samples filled with CaCO₃ of a single size. The torques of LDPE samples filled with CaCO₃ of a single size and those filled with CaCO₃ of different size distributions at different temperatures were also studied. The results showed that the flow activation energy and flow activation entropy of LDPE samples filled with CaCO₃ of different size distributions increased obviously. The increase in the flow activation entropy was used to explain the phenomenon of the process torque decreasing for LDPE samples filled with CaCO₃ of different size distributions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010