| The rotational molding industry is experiencing a rapid development. The process involves powder tumbling, melting, and distributing of polymer melt and cooling to form a solid part. The main concern in this work is to gain a better understanding of how processing conditions affect powder densification in the rotational molding process.; The uni-axial bench-scale molding machine built in our laboratory is used for studying the densification process. An experimental procedure was set in place to ensure proper control of molding conditions. The degree of densification achieved during molding was determined based on the density of the molded part and bubble content in the molded part. Density measurements were performed using an electronic densimeter MD-200s, for which, larger volume sample part gives a more accurate result. Oven temperature was found to have significant effects on the density profiles. Higher oven temperature causes larger variations in the density with the axial position in the molded parts. Small variations in the molding heating time also have important effects on the density profiles. The powder sizes were found to have a definite effect on the density of the molded parts. Powders with high fine particle content produced parts with lower density and higher bubble content. Bubble distribution along the thickness reflects the temperature changes experienced during molding cycle. Additional experimental work will be needed to confirm some of the results presented in this work. |
