Document Abstract
ANTEC Papers: 2000
0757: Modelling of Bubble Formation in Rotational Molding
C. T. Bellehumeur and J. S. Tiang Department of Chemical and Petroleum Engineering, University of Calgary Calgary, AB, Canada, T2N 1N4 cbellehu@acs.ucalgary.ca
Polymer sintering and heat transfer are fundamental phenomena in rotational molding. In the heating stage of the molding cycle, the powder particles melt, adhere to each other and sinter. During this stage, pockets of air are entrapped between the particles and form bubbles. This work aims at determining the relative effects of material properties and molding temperature on the initial sintering and bubble formation in rotational molding. The molding temperature varies strongly with the oven temperature and molded part thickness, and is determined using a lumped parameters heat transfer model (Gogos et al., 1998). The initial sintering of powder is predicted using a two-particle sintering model (Pokluda et al, 1997). The sintering model is used together with the heat transfer model to predict the level of sintering reached when an additional powder layer adheres to the melt and thus entraps air pockets which in turn will form bubbles. Results show that the initial size of the bubbles formed does not vary significantly when changing molding conditions. The polymer rheological properties seem to dominate the bubble formation process. Further results will be compared with experimental work.