Utilization of mineral fillers in high density polyethylene

Abstract

This research aims to study the utilization of mineral additives for high density polyethylene (HDPE). The mineral fillers used are calcium carbonate and talc. In addition, carbon black will also be employed. Interfacial affinity between HDPE and the applied fillers are modified by the use of a coupling agent. Titanate type of coupling agent was employed in the present study because fillers such as calcium carbonate and talc do not respond to silanes. Experimental design was based on a factorial design method to find factors and interactions that effect the mechanical and thermal properties of the filled-HDPE. A two-level full or 2k factorial design was considered to be best for the needs of the present study because it enables the possibility of assessing several factors and their interactions simultaneously. The effect of five factors were studied namely the CaCO₃ with and without pre-treatment with titanate coupling agent and carbon black. The main finding is that the mechanical properties are significantly effected. The order of the significance of the effect is as following untreated CaCO₃ > treated CaCO₃ > untreated talc > treated talc> carbon black. The thermal properties are not significantly effected by the five factors and their interactions. The CaCO₃ is selected to study the effect of mineral filler on the mechanical properties of HDPE composites. In the study, the modulus, yield stress, hardness and the heat deflection temperature increase when the filler content is increase. The value of fracture energy and the yield strain decrease when the filler content is increased. Surface treatment of CaCO₃ with titanate coupling agent enhances the adhesion between the filler and polymer surface. The suitable CaCO₃ content is in the range from 10 to 20 phr as the system still possesses adequate ductility. The best concentration of titanate coupling agent is 0.5 %.